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draft-ietf-sigtran-sua-10

Description: Request For Comments

You can download source copies of the file as follows:

draft-ietf-sigtran-sua-10.txt in text format.

Listed below is the contents of file draft-ietf-sigtran-sua-10.txt.




INTERNET-DRAFT                                    J. Loughney (Editor) 
Internet Engineering Task Force                                  Nokia 
                                                         G. Sidebottom 
                                                   gregside Consulting 
                                                          Guy Mousseau 
Issued:  27 December 2001                              Nortel Networks 
Expires: 27 June 2002                                       S. Lorusso 
                                                    Unisphere Networks 
                                                  L. Coene, G. Verwimp 
                                                               Siemens 
                                                             J. Keller 
                                                               Tekelec 
                                                            F. Escobar  
                                                              Ericsson 
                                                  W. Sully, S. Furniss 
                                                               Marconi 
                                                           B. Bidulock 
                                                   OpenSS7 Corporation 
 
                  SS7 SCCP-User Adaptation Layer (SUA) 
                    <draft-ietf-sigtran-sua-10.txt> 
 
Status of This Memo 
 
   This document is an Internet-Draft and is in full conformance with 
   all provisions of Section 10 of RFC 2026.  
    
   Internet-Drafts are working documents of the Internet Engineering 
   Task Force (IETF), its areas, and its working groups.  Note that 
   other groups may also distribute working documents as Internet-
   Drafts. 
    
   Internet-Drafts are draft documents valid for a maximum of six 
   months and may be updated, replaced, or obsoleted by other documents 
   at any time.  It is inappropriate to use Internet-Drafts as 
   reference material or to cite them other than as 'work in progress.' 
    
   The list of current Internet-Drafts can be accessed at 
   http://www.ietf.org/ietf/1id-abstracts.txt 
    
   The list of Internet-Draft Shadow Directories can be accessed at 
   http://www.ietf.org/shadow.html. 
    
   This draft expires on 27 June 2002. 
    
Abstract 
    
   This Internet Draft defines a protocol for the transport of any SS7 
   SCCP-User signalling (e.g., TCAP, RANAP, etc.) over IP using the 
   Stream Control Transport Protocol.  The protocol should be modular 
   and symmetric, to allow it to work in diverse architectures, such as 
   a Signalling Gateway to IP Signalling Endpoint architecture as well 
   as a peer-to-peer IP Signalling Endpoint architecture.  Protocol 
   elements are added to allow operation between peers in the SS7 and 
   IP domains.  

 
Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
Abstract.............................................................1 
1. Introduction......................................................3 
 1.1 Scope...........................................................3 
 1.2 Terminology.....................................................3 
 1.3 Signalling Transport Architecture...............................5 
 1.4 Services Provided by the SUA Layer..............................8 
 1.5 Internal Functions Provided in the SUA Layer...................10 
 1.6 Definition of SUA Boundaries...................................13 
2 Conventions.......................................................17 
3 Protocol Elements.................................................17 
 3.1 Common Message Header..........................................17 
 3.2 SUA Connectionless Messages....................................21 
 3.3 Connection Oriented Messages...................................25 
 3.4 Signalling Network Management (SNM) Messages...................35 
 3.5 Application Server Process State Maintenance Messages..........41 
 3.6 ASP Traffic Maintenance Messages...............................44 
 3.7 SUA Management Messages........................................47 
 3.8 Routing Key Management (RKM) Messages..........................48 
 3.9 Common Parameters..............................................51 
 3.10 SUA-Specific parameters.......................................60 
4. Procedures.......................................................77 
 4.1 Procedures to Support the SUA-User Layer.......................77 
 4.2 Receipt of Primitives from the Layer Management................78 
 4.3 AS and ASP State Maintenance...................................80 
 4.4 Routing Key Management Procedures..............................93 
 4.5 Availability and/or Congestion Status of SS7 Destination ......96 
 4.6 MTP3 Restart...................................................98 
 4.7 SCCP - SUA Interworking at the SG..............................99 
5 Examples of SUA Procedures.......................................100 
 5.1 SG Architecture...............................................100 
 5.2 IPSP Examples.................................................102 
6 Security Considerations..........................................103 
 6.1 Introduction..................................................103 
 6.2 Threats.......................................................104 
 6.3 Protecting Confidentiality....................................104 
7 IANA Considerations..............................................104 
 7.1 SCTP Payload Protocol ID......................................104 
 7.2 Port Number...................................................105 
 7.3 Protocol Extensions...........................................105 
8 Timer Values.....................................................106 
9 Acknowledgements.................................................106 
10 Authors' Addresses..............................................106 
11 References......................................................108 
Appendix A Signaling Network Architecture..........................109 
 A.1 Generalized Peer-to-Peer Network Architecture.................109 
 A.2 Signalling Gateway Network Architecture.......................110 
 A.3 Signaling Gateway Message Distribution Recommendations........112 
Copyright Statement................................................113 

 
Loughney (editor)                                           [Page 2] 
 

 
Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
1. Introduction 
    
   This draft defines a protocol for the transport SS7 SCCP [ANSI SCCP] 
   [ANSI SCCP] Users (i.e. TCAP, RANAP, etc.) signalling messages over 
   IP using the Stream Control Transmission Protocol (SCTP) [2960].  
   This protocol would be used between a Signalling Gateway (SG) and 
   Signaling Endpoint located in an IP network.  Additionally, the 
   protocol can be used to transport SS7 SCCP users between two 
   signaling endpoints located within an IP network. 
    
1.1 Scope 
    
   There is on-going integration of SCN networks and IP networks.  
   Network service providers are designing all IP architectures that 
   include support for SS7 and SS7-like signalling protocols. IP 
   provides an effective way to transport user data and for operators 
   to expand their networks and build new services. In these networks, 
   there is need for interworking between the SS7 and IP domains 
   [2719]. 
    
   This document details the delivery of SCCP-user messages (MAP & CAP 
   over TCAP [ANSI TCAP] [ITU TCAP], RANAP [RANAP], etc.) and new 3rd 
   Generation network protocol messages over IP between two signalling 
   endpoints.  Consideration is given for the transport from an SS7 
   Signalling Gateway (SG) to an IP signalling node (such as an IP-
   resident Database) as described in the Framework Architecture for 
   Signalling Transport [2719]. This protocol can also support 
   transport of SCCP-user messages between two endpoints wholly 
   contained within an IP network. 
    
   The delivery mechanism addresses the following criteria:  
    
     *    Support for transfer of SCCP-User Part messages (TCAP, RANAP, 
          etc.) 
     *    Support for SCCP connectionless service. 
     *    Support for SCCP connection oriented service. 
     *    Support for the seamless operation of SCCP-User protocol 
          peers. 
     *    Support for the management of SCTP transport associations 
          between a SG and one or more IP-based signalling nodes). 
     *    Support for distributed IP-based signalling nodes. 
     *    Support for the asynchronous reporting of status changes to 
          management. 
    
1.2 Terminology 
    
   Signalling Gateway (SG) - Network element that terminates SCN 
   signalling and transports SCCP-User signalling over IP to an IP 
   signalling endpoint.  A Signalling Gateway could be modeled as one 
   or more Signalling Gateway Processes, which are located at the 
   border of the SS7 and IP networks. Where an SG contains more than 
   one SGP, the SG is a logical entity and the contained SGPs are 
 
Loughney (editor)                                           [Page 3] 
 

 
Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
   assumed to be coordinated into a single management view to the SS7 
   network and to the supported Application Servers. 
    
   Application Server (AS) - A logical entity serving a specific 
   Routing Key.  An example of an Application Server is a virtual IP 
   database element handling all requests for a SCCP-user.  The AS 
   contains a set of one or more unique Application Server Processes, 
   of which one or more is normally actively processing traffic. 
    
   Application Server Process (ASP) - An Application Server Process 
   serves as an active or backup process of an Application Server 
   (e.g., part of a distributed signalling node or database element).  
   Examples of ASPs are MGCs, IP SCPs, or IP-based HLRs.  An ASP 
   contains an SCTP end-point and may be configured to process traffic 
   within more than one Application Server. 
    
   IP Server Process (IPSP) - A process instance of an IP-based 
   application.  An IPSP is essentially the same as an ASP, except that 
   it uses SUA in a peer-to-peer fashion.  Conceptually, an IPSP does 
   not use the services of a Signalling Gateway. 
    
   Signalling Gateway Process (SGP) - A process instance of a 
   Signalling Gateway.  It serves as an active, load-sharing or 
   broadcast process of a Signalling Gateway. 
    
   Signalling Process - A process instance that uses SUA to communicate 
   with other signalling process.  An ASP, a SGP and an IPSP are all 
   signalling processes. 
    
   Association - An association refers to an SCTP association.  The 
   association provides the transport for the delivery of SCCP-User 
   protocol data units and SUA layer peer messages. 
    
   Routing Key - The Routing Key describes a set of SS7 parameters 
   and/or parameter-ranges that uniquely defines the range of 
   signalling traffic configured to be handled by a particular 
   Application Server. An example would be where a Routing Key consists 
   of a particular SS7 SCCP SSN plus an identifier to uniquely mark the 
   network that the SSN belongs to, for which all traffic would be 
   directed to a particular Application Server.  Routing Keys are 
   mutually exclusive in the sense that a received SS7 signalling 
   message cannot be directed to more than one Routing Key.  Routing 
   Keys can be provisioned, for example, by a MIB or registered using 
   SUA's dynamic registration procedures. Routing keys MUST NOT span 
   multiple network appearances. 
    
   Routing Context - An Application Server Process may be configured to 
   process traffic within more than one Application Server.  In this 
   case, the Routing Context parameter is exchanged between the SGP and 
   the ASP (or between two ASPs), identifying the relevant Application 
   Server.  From the perspective of an SGP/ASP, the Routing Context 
   uniquely identifies the range of traffic associated with a 
 
Loughney (editor)                                           [Page 4] 
 

 
Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
   particular Application Server, which the ASP is configured to 
   receive. There is a 1:1 relationship between a Routing Context value 
   and a Routing Key within an AS.  Therefore the Routing Context can 
   be viewed as an index into an AS Table containing the AS Routing 
   Keys.  
    
   Address Mapping Function (AMF) - The AMF is an implementation 
   dependent function that is responsible for resolving the address 
   presented in the incoming SCCP/SUA message to correct SCTP 
   association for the desired endpoint. The AMF MAY use routing 
   context / rouging key information as selection criteria for the 
   appropriate SCTP association. 
    
   Fail-over - The capability to re-route signalling traffic as 
   required to an alternate Application Server Process, or group of 
   ASPs, within an Application Server in the event of failure or 
   unavailability of a currently used Application Server Process.  
   Fail-over may apply upon the return to service of a previously 
   unavailable Application Server Process. 
    
   Network Byte Order - Most significant byte first, a.k.a. Big Endian. 
    
   Layer Management - Layer Management is a nodal function that handles 
   the inputs and outputs between the SUA layer and a local management 
   entity.   
    
   Host - The computing platform that the SGP or ASP process is running 
   on. 
    
   Stream - A stream refers to an SCTP stream; a uni-directional 
   logical channel established from one SCTP endpoint to another 
   associated SCTP endpoint, within which all user messages are 
   delivered in-sequence except for those submitted to the un-ordered 
   delivery service. 
    
   Transport address - an address that serves as a source or 
   destination for the unreliable packet transport service used by 
   SCTP. In IP networks, a transport address is defined by the 
   combination of an IP address and an SCTP port number.  Note, only 
   one SCTP port may be defined for each endpoint, but each SCTP 
   endpoint may have multiple IP addresses. 
  
1.3 Signalling Transport Architecture 
    
   The framework architecture that has been defined for SCN signalling 
   transport over IP [2719] uses multiple components, including an IP 
   transport protocol, a signalling common transport protocol and an 
   adaptation module to support the services expected by a particular 
   SCN signalling protocol from its underlying protocol layer.   
    
   In general terms, the SUA architecture can be modeled as a peer-to-
   peer architecture. The first section considers the SS7-IP 
 
Loughney (editor)                                           [Page 5] 
 

 
Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
   interworking architectures for connectionless and connection- 
   oriented transport.  For this case, it is assumed that the ASP 
   initiates the establishment of the SCTP association with SG. 
    
1.3.1 Protocol Architecture for Connectionless Transport  
    
   In this architecture, the SCCP and SUA layers interface in the SG. 
   Interworking between the SCCP and SUA layers is needed to provide 
   for the transfer of the user messages as well as the management 
   messages.   
    
        ********   SS7   ***************   IP   ******** 
        * SEP  *---------*             *--------*      * 
        *  or  *         *      SG     *        * ASP  * 
        * STP  *         *             *        *      * 
        ********         ***************        ******** 
    
        +------                                 +------+ 
        | SUAP |                                | SUAP | 
        +------+         +------+------+        +------+ 
        | SCCP |         | SCCP | SUA  |        | SUA  | 
        +------+         +------+------+        +------+ 
        | MTP3 |         | MTP3 |      |        |      | 
        +------+         +------+ SCTP |        | SCTP | 
        | MTP2 |         | MTP2 |      |        |      | 
        +------+         +------+------+        +------+ 
        |  L1  |         |  L1  |  IP  |        |  IP  | 
        +------+         +------+------+        +------+ 
            |               |         |            | 
            +---------------+         +------------+ 
    
          SUAP - SCCP/SUA User Protocol (TCAP, for example) 
          STP  - SS7 Signalling Transfer Point 
    
   See Appendix A.3.1 for operation recommendations. 

1.3.1.1 SG as endpoint 
    
   In this case, the connectionless SCCP messages are routed on PC and 
   SSN.  The subsystem identified by SSN and Routing Context is 
   regarded as local to the SG.  This means from SS7 point of view, the 
   SCCP-user is located at the SG.  

1.3.1.2 SG as relay-point 
    
   A Global Title translation is executed at the SG, before the 
   destination of the message can be determined.  The actual location 
   of the SCCP-user is irrelevant to the SS7 network.  GT Translation 
   yields an "SCCP entity", from an AS can be derived.  Selection of 
   the AS is thus based on the SCCP called party address  (and possibly 
   other SS7 parameters depending on the implementation).   
 
Loughney (editor)                                           [Page 6] 
 

 
Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
    
1.3.2 Protocol Architecture for Connection-Oriented Transport  
    
   In this architecture, the SCCP and SUA layers interface in the SGP 
   to associate the two connection sections needed for the connection- 
   oriented data transfer between SEP and ASP.  Both connection 
   sections are setup when routing the Connect Request messages from 
   SEP via SGP to ASP or the other way.  The routing of the Connect 
   Request message is done in the same way as described in 1.3.1. 
    
        ********   SS7   ***************   IP   ******** 
        * SEP  *---------*             *--------*      * 
        *  or  *         *      SG     *        * ASP  * 
        * STP  *         *             *        *      * 
        ********         ***************        ******** 
    
        +------+                                +------+ 
        | SUAP |                                | SUAP | 
        +------+         +------+------+        +------+ 
        | SCCP |         | SCCP | SUA  |        | SUA  | 
        +------+         +------+------+        +------+ 
        | MTP3 |         | MTP3 |      |        |      | 
        +------|         +------+ SCTP |        | SCTP | 
        | MTP2 |         | MTP2 |      |        |      | 
        +------+         +------+------+        +------+ 
        |  L1  |         |  L1  |  IP  |        |  IP  | 
        +------+         +------+------+        +------+ 
            |               |         |            | 
            +---------------+         +------------+ 
    
          SUAP - SCCP/SUA Application Protocol (e.g. - RANAP/RNSAP) 
          STP  - SS7 Signalling Transfer Point 
    
   See Appendix A.3.2 for operation recommendations. 
    
1.3.3 All IP Architecture 
    
   This architecture can be used to carry a protocol that uses the 
   transport services of SCCP, but is contained with an IP network.  
   This allows extra flexibility in developing networks, especially 
   when interaction between legacy signalling is not needed.  The 
   architecture removes the need for signalling gateway functionality. 

 
Loughney (editor)                                           [Page 7] 
 

 
Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
    
          ********   IP   ******** 
          *      *--------*      * 
          * IPSP *        * IPSP * 
          *      *        *      * 
          ********        ******** 
         
          +------+        +------+ 
          | SUAP |        | SUAP | 
          +------+        +------+ 
          | SUA  |        | SUA  | 
          +------+        +------+ 
          | SCTP |        | SCTP | 
          +------+        +------+ 
          |  IP  |        |  IP  | 
          +------+        +------+ 
             |                | 
             +----------------+ 
    
       SUAP - SCCP/SUA Application Protocol (e.g. - RANAP/RNSAP) 
    
1.3.4 ASP Fail-over Model and Terminology 
    
   The SUA protocol supports ASP fail-over functions to support a high 
   availability of transaction processing capability. 
    
   An Application Server can be considered as a list of all ASPs 
   configured/registered to handle SCCP-user messages within a certain 
   range of routing information, known as a Routing Key.  One or more 
   ASPs in the list may normally be active to handle traffic, while 
   others may be inactive but available in the event of failure or 
   unavailability of the active ASP(s). 
    
   For operation recommendations, see Appendix A. 
    
1.4 Services Provided by the SUA Layer 
    
1.4.1 Support for the transport of SCCP-User Messages 
    
   The SUA supports the transfer of SCCP-user messages. The SUA layer 
   at the SG and at the ASP support the seamless transport the user 
   messages between the SG and the ASP. 
    
1.4.2 SCCP Protocol Class Support 
    
   Depending upon the SCCP-users supported, the SUA shall support the 4 
   possible SCCP protocol classes transparently.  The SCCP protocol 
   classes are defined as follows: 
    
     *    Protocol class 0 provides unordered transfer of SCCP-user 
          messages in a connectionless manner. 
    
 
Loughney (editor)                                           [Page 8] 
 

 
Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
     *    Protocol class 1 allows the SCCP-user to select the in-
          sequence delivery of SCCP-user messages in a connectionless 
          manner. 
    
     *    Protocol class 2 allows the bi-directional transfer of SCCP-
          user messages by setting up a temporary or permanent 
          signalling connection.   
    
     *    Protocol class 3 allows the features of protocol class 2 with 
          the inclusion of flow control.  Detection of message loss or 
          mis-sequencing is included. 
    
   Protocol classes 0 and 1 make up the SCCP connectionless service.  
   Protocol classes 2 and 3 make up the SCCP connection-oriented 
   service. 
 
1.4.3 Native Management Functions 
    
   The SUA layer provides the capability to indicate errors associated 
   with the SUA-protocol messages and to provide notification to local 
   management and the remote peer as is necessary. 
    
1.4.4 Interworking with SCCP Network Management Functions 
    
   SUA uses the existing ASP management messages for ASP status    
   handling.  The interworking with SCCP management messages consists 
   of DUNA, DAVA, DAUD, DRST, DUPU or SCON messages on receipt of SSP, 
   SSA, SST or SSC to the appropriate ASPs.  See also chapter 1.4.5. 
   The primitives below are considered to be send between the SCCP and 
   SUA management functions in the SG to trigger events in the IP and 
   SS7 domain. 
    
   Generic   |Specific   |  
   Name      |Name       |ANSI/ITU Reference                         
   ----------+-----------+--------------------------------------------- 
   N-State   |Request    |ITU-Q.711   Chap 6.3.2.3.2 (Tab 14/Q.711)    
             |Indication |ANSI-T1.112 Chap 2.3.2.3.2 (Tab 8E/T1.112.1) 
   ----------+-----------+--------------------------------------------- 
   N-Pcstate |Indication |ITU-Q.711   Chap 6.3.2.3.3 (Tab 15/Q.711)               
             |           |ANSI-T1.112 Chap 2.3.2.3.4 (Tab 8G/T1.112.1)  
   N-Coord   |Request    |ITU-Q.711   Chap 6.3.2.3.1 (Tab 13/Q.711) 
             |Indication |ANSI-T1.112 Chap 2.3.2.3.3 (Tab 8F/T1.112.1) 
             |Response   | 
             |Confirm    | 
    
1.4.5 Support for the management between the SGP and ASP. 
    
   The SUA layer should provide interworking with SCCP management 
   functions at the SG for seamless inter-operation between the SCN 
   network and the IP network.  It should: 
    

 
Loughney (editor)                                           [Page 9] 
 

 
Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
     *    Provide an indication to the SCCP-user at an ASP that a SS7 
          endpoint/peer is unreachable. 
     *    Provide an indication to the SCCP-user at an ASP that a SS7 
          endpoint/peer is reachable. 
     *    Provide congestion indication to SCCP-user at an ASP. 
     *    Provide the initiation of an audit of SS7 endpoints at the 
          SG. 
    
1.4.6 Relay function 
    
   For network scalability purposes, the SUA may be enhanced with a 
   relay functionality to determine the next hop SCTP association 
   towards the destination SUA endpoint. 
    
   The determination of the next hop may be based on Global Title 
   information (e.g. E.164 number), in analogy with SCCP GTT in SS7 
   networks, modeled in [ITU-T Q.714]. It may also be based on Hostname 
   information, IP address or pointcode contained in the called party 
   address. 
    
   This allows for greater scalability, reliability and flexibility in 
   wide-scale deployments of SUA.  The usage of a relay function is a 
   deployment decision. 
    
1.5 Internal Functions Provided in the SUA Layer 
    
   To perform its addressing and relaying capabilities, the SUA makes 
   use of an Address Mapping Function (AMF). This function is 
   considered part of SUA, but the way it is realized is left 
   implementation / deployment dependent (local tables, DNS [2916], 
   LDAP, etc.) 
    
   The AMF is invoked when a message is received at the incoming 
   interface. The AMF is responsible for resolving the address 
   presented in the incoming SCCP/SUA message to SCTP associations to 
   destinations within the IP network. The AMF will select the 
   appropriate SCTP association based upon routing context / routing 
   key information available. The destination might be the end SUA node 
   or a SUA relay node. The Routing Keys reference an Application 
   Server, which will have one or more ASPs processing traffic for the 
   AS.  The availability and status of the ASPs is handled by SUA ASP 
   management messages. 
    
   Possible SS7 address/routing information that comprise a Routing Key 
   entry includes, for example, OPC, DPC, SIO found in the MTP3 routing 
   label, SCCP subsystem number, or Transaction ID. IP addresses and 
   hostnames can also be used as Routing Key Information. 
    
   It is expected that the routing keys be provisioned via a MIB, 
   dynamic registration or external process, such as a database.  
    

 
Loughney (editor)                                           [Page 10] 
 

 
Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
1.5.1 Address Mapping at the SG 
    
   Normally, one or more ASPs are active in the AS (i.e., currently 
   processing traffic) but in certain failure and transition cases it 
   is possible that there may not be an active ASP available. The SGP 
   will buffer the message destined for this AS for a time t(r) or 
   until an ASP becomes available. When no ASP becomes available before 
   expiry of t(r), the SGP will flush the buffered messages and 
   initiate the appropriate return or refusal procedures. 
    
   If there is no match for an incoming message, a default treatment 
   MAY be specified.  Possible solutions are to provide a default 
   Application Server to direct all unallocated traffic to a (set of) 
   default ASP(s), or to drop the messages and provide a notification 
   to management. The treatment of unallocated traffic is 
   implementation dependent. 
    
1.5.2 Address Mapping at the ASP 
    
   To direct messages to the SS7 network, the ASP MAY perform an 
   address mapping to choose the proper SGP for a given message.  This 
   is accomplished by observing the Destination Point Code and other 
   elements of the outgoing message, SS7 network status, SGP 
   availability, and Routing Context configuration tables. 
    
   A Signalling Gateway may be composed of one or more SGPs. There is, 
   however, no SUA messaging to manage the status of an SGP. Whenever 
   an SCTP association to an SGP exists, it is assumed to be available.  
   Also, every SGP of one SG communicating with one ASP regarding one 
   AS provides identical SS7 connectivity to this ASP. 
    
   An ASP routes responses to the SGP that it received messages from; 
   within the routing context which it is currently active and 
   receiving traffic.  The routing context itself is used by the ASP to 
   select the SGP. 
 
1.5.3 Address Mapping Function at a Relay Node 
    
   The relay function is invoked when: 
    
     -    Routing is on Global Title 
     -    Routing is on Hostname   
     -    Routing is on SSN and PC or SSN and IP Address and the 
          address presented is not the one of the relay node 
    
   Translation/resolution of the above address information yields one   
   of the following: 
    
     -    Route on SSN: SCTP association ID towards the destination 
          node, SSN and optionally Routing Context and/or IP address. 
     -    Route on GT: SCTP association ID towards next relay node, 
          (new) GT and optionally SSN and/or Routing Context.  
 
Loughney (editor)                                           [Page 11] 
 

 
Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
     -    Routing on Hostname: SCTP association ID towards next relay 
          node, (new) Hostname and optionally SSN and/or Routing 
          Context.  
     -    A local SUA-user (combined relay/end node) 
    
   To prevent looping, an SS7 hop counter is used. The originating end 
   node (be it an SS7 or an IP node) sets the value of the SS7 hop 
   counter to the maximum value (15 or less). Each time the relay 
   function is invoked within an intermediate (relay) node, the SS7 hop 
   counter is decremented. When the value reaches zero, the return or 
   refusal procedures are invoked with reason "Hop counter violation". 
    
1.5.4 SCTP Stream Mapping 
    
   The SUA supports SCTP streams. The SG/AS needs to maintain a list of 
   SCTP and SUA-users for mapping purposes.  SCCP-users requiring 
   sequenced message transfer need to be sent over a stream supporting 
   sequenced delivery. 
    
   SUA uses stream 0 for SUA management messages.  It is OPTIONAL that 
   sequenced delivery be used to preserve the order of management 
   message delivery. 
    
   Stream selection based on protocol class: 
    
     -    Protocol class 0: SUA MAY select unordered delivery.  The    
          stream selected is based on traffic information available    
          to the SGP or ASP. 
     -    Protocol class 1: SUA MUST select ordered delivery.  The 
          stream selected is based upon the sequence parameter given by 
          the upper layer over the primitive interface and other 
          traffic information available to the SGP or ASP   
    -     Protocol classes 2 and 3: SUA MUST select ordered delivery.  
          The stream selected is based upon the source local reference 
          of the connection and other traffic information available to 
          the SGP or ASP. 
    
1.5.5 Flow Control 
    
   Local Management at an ASP may wish to stop traffic across an SCTP 
   association to temporarily remove the association from service or to 
   perform testing and maintenance activity.  The function could 
   optionally be used to control the start of traffic on to a newly 
   available SCTP association. 
    
1.5.6 Congestion Management 
    
   The SUA layer is informed of local and IP network congestion by 
   means of an implementation-dependent function (e.g., an 
   implementation-dependent indication from the SCTP of IP network 
   congestion).  
    
 
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   At an ASP or IPSP, the SUA layer indicates congestion to local SCCP-
   Users by means of an appropriate SCCP primitive (e.g. N-INFORM, N-
   NOTICE), as per current SCCP procedures, to invoke appropriate upper 
   layer responses.  When an SG determines that the transport of SS7 
   messages is encountering congestion, the SG MAY trigger SS7 SCCP 
   Congestion messages to originating SS7 nodes, per the congestion 
   procedures of the relevant SCCP standard. The triggering of SS7 SCCP 
   Management messages from an SG is an implementation-dependent 
   function. 
    
   The SCCP layer at an ASP or IPSP MAY indicate local congestion to an 
   SUA peer with an SCON message.  When an SG receives a congestion 
   message (SCON) from an ASP, and the SG determines that an endpoint 
   is now encountering congestion, it MAY trigger congestion procedures 
   of the relevant SCCP standard. 
    
1.6 Definition of SUA Boundaries 
 
1.6.1 Definition of the upper boundary 
    
   The following primitives are supported between the SUA and an SCCP-
   user (a reference to ITU and ANSI sections where these primitives 
   and corresponding parameters are described, is also given): 
    
   Generic     |Specific  |  
   Name        |Name      |ANSI/ITU Reference                                   
   ------------+----------+-------------------------------------------    
   N-Connect   |Request   |ITU-Q.711   Chap 6.1.1.2.2 (Tab 2/Q.711)      
               |Indication|ANSI-T1.112 Chap 2.1.1.2.2 (Tab 2/T1.112.1)   
               |Response  |  
               |Confirm   |  
   ------------+----------+------------------------------------------- 
   N-Data      |Request   |ITU-Q.711   Chap 6.1.1.2.3 (Tab 3/Q.711)      
               |Indication|ANSI-T1.112 Chap 2.1.1.2.3 (Tab 3/T1.112.1)   
   ------------+----------+------------------------------------------- 
   N-Expedited |Request   |ITU-Q.711   Chap 6.1.1.2.3 (Tab 4/Q.711)      
   Data        |Indication|ANSI-T1.112 Chap 2.1.1.2.3 (Tab 4/T1.112.1)   
   ------------+----------+------------------------------------------- 
   N-Reset     |Request   |ITU-Q.711   Chap 6.1.1.2.3 (Tab 5/Q.711)      
               |Indication|ANSI-T1.112 Chap 2.1.1.2.3 (Tab 5/T1.112.1)   
               |Response  |  
               |Confirm   |  
   ------------+----------+------------------------------------------- 
   N-Disconnect|Request   |ITU-Q.711   Chap 6.1.1.2.4 (Tab 6/Q.711)      
               |Indication|ANSI-T1.112 Chap 2.1.1.2.4 (Tab 6/T1.112.1) 
   ------------+----------+------------------------------------------- 
   N-Inform    |Request   |ITU-Q.711   Chap 6.1.1.3.1 (Tab 7/Q.711)     
               |Indication|ANSI-T1.112 Chap 2.1.1.2.5 (Tab 6A/T1.112.1) 
   ------------+----------+------------------------------------------- 
   N-Unit Data |Request   |ITU-Q.711   Chap 6.2.2.3.1 (Tab 10/Q.711)     
               |Indication|ANSI-T1.112 Chap 2.2.2.3.1 (Tab 8A/T1.112.1) 
   ------------+----------+------------------------------------------- 
 
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   N-Notice    |Indication|ITU-Q.711   Chap 6.2.2.3.2 (Tab 11/Q.711)     
               |          |ANSI-T1.112 Chap 2.2.2.3.2 (Tab 8B/T1.112.1) 
    
1.6.2 Definition of the lower boundary 
    
   The upper layer primitives provided by the SCTP are provided in 
   [SCTP]. 
    
1.6.3 Definition of the Boundary between SUA and Layer Management 
    
   M-SCTP_ESTABLISH request 
   Direction: LM -> SUA 
   Purpose:  LM requests ASP to establish an SCTP association with its             
             peer. 
    
   M-STCP_ESTABLISH confirm  
   Direction: SUA -> LM 
   Purpose:  ASP confirms to LM that it has established an SCTP 
             association with its peer. 
    
   M-SCTP_ESTABLISH indication  
   Direction: SUA -> LM 
   Purpose:  SUA informs LM that a remote ASP has established an SCTP             
             association. 
    
   M-SCTP_RELEASE request  
   Direction: LM -> SUA 
   Purpose:  LM requests ASP to release an SCTP association with its             
             peer. 
    
   M-SCTP_RELEASE confirm 
   Direction: SUA -> LM 
   Purpose:  ASP confirms to LM that it has released SCTP association 
             with its peer. 
    
   M-SCTP_RELEASE indication 
   Direction: SUA -> LM 
   Purpose:  SUA informs LM that a remote ASP has released an SCTP             
             Association or the SCTP association has failed. 
    
   M-SCTP RESTART indication 
   Direction: SUA -> LM 
   Purpose:  SUA informs LM that an SCTP restart indication has been 
             received. 
    
   M-SCTP_STATUS request  
   Direction: LM -> SUA 
   Purpose:  LM requests SUA to report the status of an SCTP 
             association. 
    
   M-SCTP_STATUS confirm  
   Direction: SUA -> LM 
 
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   Purpose:  SUA responds with the status of an SCTP association. 
    
   M-SCTP STATUS indication 
   Direction: SUA -> LM 
   Purpose:  SUA reports the status of an SCTP association. 
    
   M-ASP_STATUS request  
   Direction: LM -> SUA 
   Purpose:  LM requests SUA to report the status of a local or remote  
               ASP. 
    
   M-ASP_STATUS confirm  
   Direction: SUA -> LM 
   Purpose:  SUA reports status of local or remote ASP. 
    
   M-AS_STATUS request  
   Direction: LM -> SUA 
   Purpose:  LM requests SUA to report the status of an AS. 
    
   M-AS_STATUS confirm  
   Direction: SUA -> LM 
   Purpose:  SUA reports the status of an AS. 
    
   M-NOTIFY indication  
   Direction: SUA -> LM 
   Purpose:  SUA reports that it has received a Notify message from its 
             peer. 
    
   M-ERROR indication  
   Direction: SUA -> LM 
   Purpose:  SUA reports that it has received an Error message from its 
             peer or that a local operation has been unsuccessful. 
    
   M-ASP_UP request  
   Direction: LM -> SUA 
   Purpose:  LM requests ASP to start its operation and send an ASP Up 
             message to its peer. 
    
   M-ASP_UP confirm 
   Direction: SUA -> LM 
   Purpose:  ASP reports that is has received an ASP UP Ack message 
             from its peer. 
    
   M-ASP_UP indication 
   Direction: SUA -> LM 
   Purpose:  SUA reports it has successfully processed an incoming ASP  
             Up message from its peer. 
    
   M-ASP_DOWN request  
   Direction: LM -> SUA 
   Purpose:  LM requests ASP to stop its operation and send an ASP Down  
             message to its peer. 
 
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   M-ASP_DOWN confirm 
   Direction: SUA -> LM 
   Purpose:  ASP reports that is has received an ASP Down Ack message  
             from its peer. 
    
   M-ASP_DOWN indication 
   Direction: SUA -> LM 
   Purpose:  SUA reports it has successfully processed an incoming ASP 
             Down message from its peer, or the SCTP association has 
             been lost/reset. 
    
   M-ASP_ACTIVE request 
   Direction: LM -> SUA 
   Purpose:  LM requests ASP to send an ASP Active message to its peer. 
    
   M-ASP_ACTIVE confirm 
   Direction: SUA -> LM 
   Purpose:  ASP reports that is has received an ASP Active Ack message 
             from its peer. 
    
   M-ASP_ACTIVE indication 
   Direction: SUA -> LM 
   Purpose:  SUA reports it has successfully processed an incoming ASP  
             Active message from its peer. 
    
   M-ASP_INACTIVE request 
   Direction: LM -> SUA 
   Purpose:  LM requests ASP to send an ASP Inactive message to its             
             peer. 
    
   M-ASP_INACTIVE confirm 
   Direction: LM -> SUA 
   Purpose:  ASP reports that is has received an ASP Inactive            
             Ack message from its peer. 
    
   M-ASP_INACTIVE indication 
   Direction: SUA -> LM 
   Purpose:  SUA reports it has successfully processed an incoming ASP             
             Inactive message from its peer. 
    
   M-AS_ACTIVE indication 
   Direction: SUA -> LM 
   Purpose:  SUA reports that an AS has moved to the AS-ACTIVE state. 
    
   M-AS_INACTIVE indication 
   Direction: SUA -> LM 
   Purpose: SUA reports that an AS has moved to the AS-INACTIVE state. 
    
   M-AS_DOWN indication 
   Direction: SUA -> LM 
   Purpose: SUA reports that an AS has moved to the AS-DOWN state. 
 
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   If dynamic registration of RK is supported by the SUA layer, the 
  layer MAY support the following additional primitives: 
    
   M-RK_REG request 
   Direction: LM -> SUA 
   Purpose:  LM requests ASP to register RK(s) with its peer by sending 
             REG REQ message 
    
   M-RK_REG confirm 
   Direction: SUA -> LM 
   Purpose:  ASP reports that it has received REG RSP message with 
             registration status as successful from its peer. 
    
   M-RK_REG indication 
   Direction: SUA -> LM 
   Purpose:  SUA informs LM that it has successfully processed an 
             incoming REG REQ message. 
    
   M-RK_DEREG request 
   Direction: LM -> SUA 
   Purpose:  LM requests ASP to deregister RK(s) with its peer by 
             sending DEREG REQ message. 
    
   M-RK_DEREG confirm 
   Direction: SUA -> LM 
   Purpose:  ASP reports that it has received DEREG REQ message with 
             deregistration status as successful from its peer. 
    
   M-RK_DEREG indication 
   Direction: SUA -> LM 
   Purpose:  SUA informs LM that it has successfully processed an 
             incoming DEREG REQ from its peer. 
    
2 Conventions 
    
   The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, 
   SHOULD NOT, RECOMMENDED, NOT RECOMMENDED, MAY, and OPTIONAL, when 
   they appear in this document, are to be interpreted as described in 
   [RFC2119]. 
    
3 Protocol Elements 
    
   The general message format includes a Common Message Header together 
   with a list of zero or more parameters as defined by the Message 
   Type. 
      
   For forward compatibility, all Message Types may have attached 
   parameters even if none are specified in this version.  
    
3.1 Common Message Header 
    
 
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   The protocol messages for the SCCP-User Adaptation Protocol requires 
   a message structure which contains a version, message class, message 
   type, message length and message contents. This message header is 
   common among all signalling protocol adaptation layers:  
    
      0                   1                   2                   3 
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |    Version    |   Reserved    | Message Class | Message Type  | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |                        Message Length                         | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |                         Message Data                          | 
    
   Note that the 'data' portion of SUA messages SHALL contain SCCP-User 
   data, not the encapsulated SCCP message. 
    
   Optional parameters can only occur at most once in an SUA message. 
    
3.1.1 SUA Protocol Version  
    
   The version field (ver) contains the version of the SUA adaptation 
   layer.  The supported versions are:  
    
     1   SUA version 1.0  
    
3.1.2 Message Classes 
    
   Message Classes 
    
     0         SUA Management (MGMT) Message 
     1         Reserved 
     2         Signalling Network Management (SNM) Messages 
     3         ASP State Maintenance (ASPSM) Messages 
     4         ASP Traffic Maintenance (ASPTM) Messages 
     5         Reserved 
     6         Reserved 
     7         Connectionless Messages  
     8         Connection-Oriented Messages 
     9         Routing Key Management (RKM) Messages. 
     10 - 127  Reserved by the IETF 
     128 - 255 Reserved for IETF-Defined Message Class Extensions 
    
3.1.3 Message Types 
    
   SUA Management Messages  
    
     0         Error (ERR)  
     1         Notify (NTFY) 
     2 - 127   Reserved by the IETF 
     128- 255  Reserved for IETF-Defined Message Class Extensions 
      
 
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   Signalling Network Management (SNM) Messages  
    
     0         Reserved 
     1         Destination Unavailable (DUNA) 
     2         Destination Available (DAVA) 
     3         Destination State Audit (DAUD) 
     4         Network Congestion (SCON) 
     5         Destination User Part Unavailable (DUPU) 
     6         Destination Restricted (DRST) 
     7 - 127   Reserved by the IETF 
     128 - 255 Reserved for IETF-Defined Message Class Extensions 
      
   Application Server Process State Maintenance (ASPSM) Messages  
    
     0         Reserved 
     1         ASP Up (UP) 
     2         ASP Down (DOWN)          
     3         Heartbeat (BEAT) 
     4         ASP Up Ack (UP ACK) 
     5         ASP Down Ack (DOWN ACK) 
     6         Heartbeat Ack (BEAT ACK) 
     7 - 127   Reserved by the IETF 
     128 - 255 Reserved for IETF-Defined Message Class Extensions 
      
   ASP Traffic Maintenance (ASPTM) Messages 
    
     0         Reserved 
     1         ASP Active (ACTIVE) 
     2         ASP Inactive (INACTIVE) 
     3         ASP Active Ack (ACTIVE ACK)  
     4         ASP Inactive Ack (INACTIVE ACK) 
     5 - 127   Reserved by the IETF 
     128 - 255 Reserved for IETF-Defined Message Class Extensions 
    
   Routing Key Management (RKM) Messages 
    
     0         Reserved 
     1         Registration Request (REG REQ) 
     2         Registration Response (REG RSP) 
     3         Deregistration Request (DEREG REQ) 
     4         Deregistration Response (DEREG RSP) 
     5 - 127   Reserved by the IETF 
     128 - 255 Reserved for IETF-Defined Message Class Extensions 
      
   Connectionless (CL) Messages  
    
     0         Reserved 
     1         Connectionless Data Transfer (CLDT)  
     2         Connectionless Data Response (CLDR)  
     3 - 127   Reserved by the IETF 
     128 - 255 Reserved for IETF-Defined Message Class Extensions 
      
 
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   Connection-Oriented (CO) Messages  
    
     0         Reserved 
     1         Connection Request (CORE)  
     2         Connection Acknowledge (COAK) 
     3         Connection Refused (COREF)  
     4         Release Request (RELRE)  
     5         Release Complete (RELCO)  
     6         Reset Confirm (RESCO)  
     7         Reset Request (RESRE)  
     8         Connection Oriented Data Transfer (CODT) 
     9         Connection Oriented Data Acknowledge (CODA) 
     10        Connection Oriented Error (COERR) 
     11        Inactivity Test (COIT) 
     12 - 127  Reserved by the IETF 
     128 - 255 Reserved for IETF-Defined Message Class Extensions 
      
3.1.4 Message Length  
    
   The Message Length defines the length of the message in octets, 
   including the header and including all padding bytes. Message Length 
   is a 32-bit identifier. 
    
3.1.5 Tag-Length-Value Format 
    
   SUA messages consist of a Common Header followed by zero or more 
   parameters, as defined by the message type.  The Tag-Length-Value 
   (TLV) parameters contained in a message are defined in a Tag-Length-
   Value format as shown below.   
    
      0                   1                   2                   3 
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |          Parameter Tag        |       Parameter Length        | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     \                                                               \ 
     /                       Parameter Value                         / 
     \                                                               \ 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameter Tag: 16 bits (unsigned integer) 
    
      Tag field is a 16-bit identifier of the type of parameter. It 
      takes a value of 0 to 65535.  
    
   Parameter Length: 16 bits (unsigned integer) 
    
     The Parameter Length field contains the size of the parameter in 
     bytes, including the Parameter Tag, Parameter Length, and 
     Parameter Value fields. The Parameter Length does not include any 
     padding bytes. However, composite parameters will contain all 

 
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     padding bytes, since all parameters contained within this 
     composite parameter will be considered multiples of 4 bytes. 
      
   Parameter Value: variable-length. 
    
     The Parameter Value field contains the actual information to be 
     trasnfered in the parameter. 
      
     The total length of a parameter (including Tag, Parameter Length 
     and Value fields) MUST be a multiple of 4 bytes. If the length of 
     the parameter is not a multiple of 4 bytes, the sender pads the 
     parameter at the end (i.e., after the Parameter Value field) with 
     all zero bytes. The length of the padding is NOT included in the 
     parameter length field. A sender should NEVER pad with more than 3 
     bytes. The receiver MUST ignore the padding bytes. 
          
   Implementation note: the use of TLV in principle allows the 
   parameters to be placed in a random order in the message. However, 
   some guidelines should be considered for easy processing in the 
   following order: 
    
     -    Parameters needed to correctly process other message 
          parameters, preferably should precede these parameters (such 
          as Routing Context). 
     -    Mandatory parameters preferably SHOULD precede any optional 
          parameters. 
     -    The data parameter will normally be the final one in the 
          message. 
     -    The receiver SHOULD accept parameters in any order, except 
          where explicitly mandated. 
 
3.2 SUA Connectionless Messages 
    
   The following section describes the SUA Connectionless transfer 
   messages and parameter contents.  The general message format 
   includes a Common Message Header together with a list of zero or 
   more parameters as defined by the Message Type.  All Message Types 
   can have attached parameters.   
    
3.2.1 Connectionless Data Transfer (CLDT) 
    
   This message transfers data between one SUA to another. 
    
     

 
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      0                   1                   2                   3  
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |          Tag = 0x0006         |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0115          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                         Protocol Class                        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0102          |            Length             |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      /                        Source Address                         /  
      \                                                               \  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |         Tag = 0x0103          |            Length             |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      /                     Destination Address                       /  
      \                                                               \  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |         Tag = 0x0116         |             Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                        Sequence Control                       | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0101          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                         SS7 Hop Count                         |   
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0113          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                          Importance                           | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    
      |         Tag = 0x0114          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                      Message Priority                         | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    
      |         Tag = 0x0013          |            Length             |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |                         Correlation ID                        |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    
      |         Tag = 0x0117          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                          Segmentation                         | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x010b          |            Length             |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      /                             Data                              /  
      \                                                               \  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
    
 
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   Parameters 
     Routing Context               Mandatory 
     Protocol Class                Mandatory 
     Source Address                Mandatory 
     Destination Address           Mandatory 
     Sequence Control              Mandatory 
     SS7 Hop Count                 Optional 
     Importance                    Optional 
     Message Priority              Optional 
     Correlation ID                Optional 
     Segmentation                  Optional 
     Data                          Mandatory 
    
   Implementation note: This message covers the following SCCP 
   messages: unitdata (UDT), extended unitdata (XUDT), long unitdata 
   (LUDT). 
 
3.2.2 Connectionless Data Response (CLDR) 
    
   This message is used as a response message by the peer to report 
   errors in the received CLDT message, when the return on error option 
   is set. 
    

 
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       0                   1                   2                   3  
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |          Tag = 0x0006         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0106          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                           SCCP Cause                          | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0102          |             Length            |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      /                        Source Address                         /  
      \                                                               \  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |         Tag = 0x0103          |             Length            |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      /                     Destination Address                       /  
      \                                                               \  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |         Tag = 0x0101          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                         SS7 Hop Count                         |   
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0113          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                          Importance                           | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    
      |         Tag = 0x0114          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                      Message Priority                         | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    
      |         Tag = 0x0013          |             Length            |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                         Correlation ID                        |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   
      |         Tag = 0x0117          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                          Segmentation                         | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x010b          |             Length            |   
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 
      /                             Data                              /  
      \                                                               \  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
    
   Parameters 
     Routing Context               Mandatory 
     SCCP Cause                    Mandatory 
     Source Address                Mandatory 
 
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     Destination Address           Mandatory 
     SS7 Hop Count                 Optional 
     Importance                    Optional 
     Message Priority              Optional 
     Correlation ID                Optional 
     Segmentation                  Optional 
     Data                          Optional 
    
   Implementation note: This message covers the following SCCP 
   messages: unitdata service (UDTS), extended unitdata service (XUDTS) 
   and long unitdata service (LUDTS). 
    
3.3 Connection Oriented Messages 
    
3.3.1 Connection Oriented Data Transfer (CODT) 
 
   This message transfers data between one SUA to another for 
   connection-oriented service. 
    
       0                   1                   2                   3  
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |          Tag = 0x0006         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |         Tag = 0x0107          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                        Sequence Number                        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0105          |             Length            |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |                 Destination Reference Number                  |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |         Tag = 0x0114          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                      Message Priority                         | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    
      |         Tag = 0x0013          |             Length            |   
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   
      |                        Correlation ID                         |   
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   
      |         Tag = 0x010b          |             Length            |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      /                             Data                              /  
      \                                                               \  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
    
   Parameters 
     Routing Context               Mandatory 
     Sequence Number               Optional *1 
 
Loughney (editor)                                           [Page 25] 
 

 
Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
     Destination Reference Number  Mandatory  
     Message Priority              Optional 
     Correlation ID                Optional 
     Data                          Mandatory 
 
   NOTE *1:   This parameter is not present in case of Expedited Data 
              (ED). 
    
   Implementation note: In order for the CODT to represent DT1, DT2 and 
   ED messages, the following conditions MUST be met: 
    
   DT1 is represented by a CODT when: 
     Sequence Number parameter is present (contains "more" indicator). 
    
   DT2 is represented by a CODT when: 
     Sequence Number parameter is present (contains P(S), P(R) and more 
    indicator) 
    
   ED is represented by a CODT with: 
     Sequence Number parameter is not present 
 
3.3.2 Connection Oriented Data Acknowledge (CODA) 
    
   This message is used to acknowledge receipt of data by the peer.  
   This message is used only with protocol class 3. 
    
       0                   1                   2                   3  
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x0006         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0105          |             Length            |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |                 Destination Reference Number                  |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |         Tag = 0x0108          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                   Receive Sequence Number                     | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x010A          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                            Credit                             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     Routing Context               Mandatory 
     Destination Reference Number  Mandatory 
     Receive Sequence Number       Optional *1 
     Credit                        Mandatory *1 
 
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Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
    
   NOTE *1:    Mandatory when representing Data Acknowledgement (AK). 
    
   Implementation note: In order for the CODA to represent DA and EA 
   messages, the following conditions MUST be met: 
    
   DA is represented by a CODA when: 
     Receive Sequence Number parameter is present (contains P(S), P(R) 
    and more indicator) 
    
   EA is represented by a CODA when: 
     Receive Sequence Number parameter is not present 
    
3.3.3 Connection Request (CORE) 
    
   This message is used for establishing a signalling connection 
   between two peer endpoints. 
    
        0                   1                   2                   3 
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x0006         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0115          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                         Protocol Class                        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0104          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                   Source Reference Number                     | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0103          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                     Destination Address                       / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0116          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                        Sequence Control                       | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0107          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                        Sequence Number                        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0102          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                        Source Address                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
 
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Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
      |         Tag = 0x0101          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                         SS7 Hop Count                         |   
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0113          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                          Importance                           | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    
      |         Tag = 0x0114          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                      Message Priority                         | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    
      |         Tag = 0x010A          |           Length              | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                            Credit                             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x010b          |           Length              | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                             Data                              / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     Routing Context               Mandatory 
     Protocol Class                Mandatory 
     Source Reference Number       Mandatory 
     Destination Address           Mandatory 
     Sequence Control              Mandatory 
     Sequence Number               Optional *1 
     Source Address                Optional  
     SS7 Hop Count                 Optional 
     Importance                    Optional 
     Message Priority              Optional 
     Credit                        Optional *1 
     Data                          Optional 
    
    
   NOTE *1: Manditory for protocol class 3 only. 
    
   Implementation note: This message covers the following SCCP message: 
   Connection Request (CR). 
    
3.3.4 Connection Acknowledge (COAK) 
    
   This message is used to acknowledge a connection request from the 
   peer endpoint. 

 
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Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x0006         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0115          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                         Protocol Class                        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0105          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                 Destination Reference Number                  | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0104          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                   Source Reference Number                     | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x01116          |            Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                        Sequence Control                       | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x010A          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                            Credit                             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0113          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                          Importance                           | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    
      |         Tag = 0x0114          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                      Message Priority                         | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    
      |         Tag = 0x0103          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                     Destination Address                       / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x010b          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                             Data                              / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     Routing Context               Mandatory 
     Protocol Class                Mandatory 
     Destination Reference Number  Mandatory 
 
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Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
     Source Reference Number       Mandatory 
     Sequence Control              Mandatory 
     Credit                        Mandatory *2 
     Importance                    Optional 
     Message Priority              Optional 
     Destination Address           Optional *1 
     Data                          Optional 
    
   NOTE *1:    Destination Address parameter will be present in case 
               that the received CORE message conveys the Source 
               Address parameter.  
    
   NOTE *2:    Only applicable for protocol class 3. 
    
   Implementation note: This message covers the following SCCP message: 
   Connection Confirm (CC). 
    
3.3.5 Connection Refused (COREF) 
    
   This message is used to refuse a connection request between two peer 
   endpoints. 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x0006         |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0105          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                 Destination Reference Number                  | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0106          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                           SCCP Cause                          | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0103          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                     Destination Address                       / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0113          |             Length = 8        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                          Importance                           | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    
      |         Tag = 0x010b          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                             Data                              / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
 
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Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
    
   Parameters 
     Routing Context                    Mandatory 
     Destination Reference Number       Mandatory 
     SCCP Cause                         Mandatory 
     Destination Address                Optional *1 
     Importance                         Optional 
     Data                               Optional 
    
   Note *1:   Destination Address parameter will be present in case 
              that the received CORE message conveys the Source Address 
              parameter.  
    
   Implementation note: This message covers the following SCCP message: 
   Connection REFused (CREF). 
    
3.3.6 Release Request (RELRE) 
    
   This message is used to request a signalling connection between two 
   peer endpoints be released.  All associated resources can then be 
   released. 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |          Tag = 0x0006         |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0105          |             Length            |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |                 Destination Reference Number                  |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |         Tag = 0x0104          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                   Source Reference Number                     | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0106          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                          SCCP Cause                           | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0113          |             Length = 8        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                          Importance                           | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    
      |         Tag = 0x010b          |             Length            |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      /                             Data                              /  
      \                                                               \  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
    
 
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   Parameters 
     Routing Context               Mandatory 
     Destination Reference Number  Mandatory  
     Source Reference Number       Mandatory  
     SCCP Cause                    Mandatory  
     Importance                    Optional 
     Data                          Optional 
    
   Implementation note: This message covers the following SCCP message: 
   connection ReLeaSeD (RLSD). 
    
3.3.7 Release Complete (RELCO) 
    
   This message is used to acknowledge the release of a signalling 
   connection between two peer endpoints.  All associated resources 
   should be released. 
      
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |          Tag = 0x0006         |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0105          |             Length            |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |                 Destination Reference Number                  |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |         Tag = 0x0104          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                   Source Reference Number                     | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0113          |             Length = 8        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                          Importance                           | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    
    
   Parameters 
     Routing Context               Mandatory 
     Destination Reference Number  Mandatory  
     Source Reference Number       Mandatory  
     Importance                    Optional 
    
   Implementation note: This message covers the following SCCP message: 
   ReLease Complete (RLC). 
    
3.3.8 Reset Request (RESRE) 
    
   This message is used to indicate that the sending SCCP/SUA wants to 
   initiate a reset procedure (re-initialization of sequence numbers) 
   to the peer endpoint. 
 
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       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |          Tag = 0x0006         |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0105          |             Length            |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |                 Destination Reference Number                  |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |         Tag = 0x0104          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                     Source Reference Number                   | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0106          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                           SCCP Cause                          | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     Routing Context               Mandatory                      
     Destination Reference Number  Mandatory  
     Source Reference Number       Mandatory  
     SCCP Cause                    Mandatory 
      
   Implementation note: This message covers the following SCCP message: 
   ReSet Request (RSR). 
    
3.3.9 Reset Confirm (RESCO) 
    
   This message is used to confirm the Reset Request. 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x0006         |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |         Tag = 0x0105          |             Length            |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |                 Destination Reference Number                  |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |         Tag = 0x0104          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                   Source Reference Number                     | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
 
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Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
   Parameters 
     Routing Context               Mandatory 
     Destination Reference Number  Mandatory  
     Source Reference Number       Mandatory  
      
   Implementation note: This message covers the following SCCP message: 
   ReSet Confirmation (RSC). 
      
3.3.10 Connection Oriented Error (COERR) 
    
   The COERR message is sent to indicate a protocol data unit error. 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |         Tag = 0x0006          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0105          |             Length            |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |                 Destination Reference Number                  |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |         Tag = 0x0106          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                          SCCP Cause                           | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     Routing Context               Mandatory 
     Destination Reference Number  Mandatory 
     SCCP Cause                    Mandatory  
    
   Implementation note: This message covers the following SCCP message: 
   Protocol Data Unit ERRor (ERR). 
    
3.3.11 Connection Oriented Inactivity Test (COIT) 
    
   This message is used for auditing the signalling connection state 
   and the consistency of connection data at both ends of the 
   signalling connection. 
     

 
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Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0006          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0115          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                         Protocol Class                        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0104          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                   Source Reference Number                     | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0105          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                 Destination Reference number                  | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0107          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                        Sequence number                        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x010A          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                            Credit                             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     Routing Context               Mandatory 
     Protocol Class                Mandatory 
     Source Reference Number       Mandatory 
     Destination Reference number  Mandatory 
     Sequence Number               Mandatory *1 
     Credit                        Mandatory *1 
    
   NOTE *1:   Information in these parameter fields reflects those 
              values sent in the last data form 2 or data 
              acknowledgement message. They are ignored if the protocol 
              class indicates class 2.  
    
   Implementation note: This message covers the following SCCP message: 
   Inactivity Test (IT). 
    
3.4 Signalling Network Management (SNM) Messages 
    
3.4.1 Destination Unavailable (DUNA) 
    
   In the scope of SUA, this message is covered by the PC- or N-state 
   indication passed between SCCP and local SCCP-user. The DUNA message 
 
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Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
   is sent from the SG or relay node to all concerned ASPs (servicing 
   SCCP-users considered local to the SG or relay node, see chapter 
   1.3.1.1), when a destination or SCCP-user has become unreachable.  
   The SUA-User at the ASP is expected to stop traffic to the affected 
   destination or SCCP-user through the SG or relay node initiating the 
   DUNA.   
    
   The format for DUNA Message parameters is as follows: 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0006          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0012          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                        Affected Point Code                    / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x8003          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                              SSN                              | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0112          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                              SMI                              | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0004          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                          Info String                          /                                                                               
\                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     Routing Context               Optional 
     Affected Point Code           Mandatory *1 
     SSN                           Optional *1 
     SMI                           Optional 
     Info String                   Optional 
    
   Note 1:    When the SSN is included, the DUNA message corresponds to 
              the SCCP N-STATE primitive. When SSN is not, the DUNA 
              message corresponds to the SCCP N-PCSTATE primitive.  The 
              Affected Point Code can only contain one point code when 
              SSN is present. 
                
3.4.2 Destination Available (DAVA) 
    

 
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Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
   In the scope of SUA, this message is covered by the PC- and N-state 
   indication passed between SCCP and local SCCP-user. The DAVA message 
   is sent from the SG or relay node to all concerned ASPs (servicing 
   SCCP-users considered local to the SG or relay node, see chapter 
   1.3.1.1) to indicate that a destination (PC or SCCP-user) is now 
   reachable. The ASP SUA-User protocol is expected to resume traffic 
   to the affected destination through the SG or relay node initiating 
   the DAVA.  
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0006          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0012          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                        Affected Point Code                    / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x8003          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                              SSN                              | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0112          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                              SMI                              | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0004          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                          Info String                          /                                                                               
\                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     Routing Context               Optional  
     Affected Point Code           Mandatory *1 
     SSN                           Optional *1 
     SMI                           Optional 
     Info String                   Optional 
    
   Note 1:    When the SSN is included, the DAVA message corresponds to 
              the SCCP N-STATE primitive. When SSN is not included, the 
              DAVA message corresponds to the SCCP N-PCSTATE primitive. 
              The Affected Point Code can only contain one point code 
              when SSN is present. 
    
3.4.3 Destination State Audit (DAUD) 
    

 
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   The DAUD message can be sent from the ASP to the SG (or relay node) 
   to query the availability state of the routes to an affected 
   destination. A DAUD may be sent periodically after the ASP has 
   received a DUNA, until a DAVA is received. The DAUD can also be sent 
   when an ASP recovers from isolation from the SG (or relay node). 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0006          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0012          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                        Affected Point Code                    / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x8003          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                              SSN                              | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0112          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                              SMI                              | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0004          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                          Info String                          /                                                                               
\                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     Routing Context               Optional  
     Affected Point Code           Mandatory *1 
     SSN                           Optional *1 
     SMI                           Optional 
     Info String                   Optional 
    
   Note 1:    If the SSN is present, the DAUD is "soliciting" N-PCSTATE 
              primitives, otherwise it is "soliciting" N-PCSTATE 
              primitives.  The Affected Point Code can only contain one 
              point code when SSN is present. 
    
3.4.4 Network Congestion (SCON) 
    
   The SCON message can be sent from the SG or relay node to all 
   concerned ASPs to indicate that the congestion level in the SS7 
   network to a specified destination has changed. 
    
       0                   1                   2                   3 
 
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       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |         Tag = 0x0006          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0012          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                        Affected Point Code                    / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x8003          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                              SSN                              | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x000F          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                       Congestion Level                        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0112          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                              SMI                              | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0004          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                          Info String                          / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     Routing Context               Optional 
     Affected Point Code           Mandatory *1 
     SSN                           Optional *1 
     Congestion Level              Mandatory 
     SMI                           Optional 
     Info String                   Optional 
 
   Note 1:    When the SSN is included, the SCON message corresponds to 
              the SCCP N-STATE primitive. When SSN is not included, the 
              SCON message corresponds to the SCCP N-PCSTATE primitive. 
              The Affected Point Code can only contain one point code 
              when SSN is present. 
    
3.4.5 Destination User Part Unavailable (DUPU) 
    
   The DUPU message is used by an SG to inform an ASP that a remote 
  peer at an SS7 node is unavailable. 
    
   The format for DUPU message parameters is as follows: 
    
       0                   1                   2                   3 
 
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       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0006          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0012          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                        Affected Point Code                    / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x010c          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                           User/Cause                          | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0004          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      \                                                               \ 
      /                          INFO String                          / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     Routing Context               Optional 
     Affected Point Code           Mandatory *1 
     User/Cause                    Mandatory 
     Info String                   Optional 
 
   Note 1:    The DUPU corresponds to the SCCP N-PCSTATE primitive.  
    
3.4.6 Destination Restricted (DRST) 
 
   The DRST message is optionally sent from the SG to all concerned 
   ASPs to indicate that the SG has determined that one or more 
   destinations are now restricted from the point of view of the SG, or 
   in response to a DAUD message if appropriate. The SUA layer at the 
   ASP is expected to send traffic to the affected destination via an 
   alternate SGP of equal priority, but only if such an alternate route 
   exists and is available. If the affected destination is currently 
   considered unavailable by the ASP, the peer should be informed that 
   traffic to the affected destination can be resumed.  In this case, 
   the SUA layer should route the traffic through the SGP initiating 
   the DRST message. 
    
   This message is optional for the SGP to send and it is optional for 
   the ASP to act on any information received in the message.  

 
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       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0006          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0012          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                        Affected Point Code                    / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x8003          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                              SSN                              | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0004          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                          Info String                          / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     Routing Context               Optional 
     Affected Point Code           Mandatory *1 
     SSN                           Optional *1 
     Info String                   Optional 
    
  Note 1:    The Affected Point Code referes to the node to which 
              become restricted or which has requested coordinated 
              service outgage.  When SSN is included in the Destination 
              Address parameter, the DRST message corresponds to the 
              SCCP N-COORD primitive.  If the SMI parameter is also 
              included in the message, the DRST message corresponds to 
              the N-COORD Request and N-COORD Indication primitives, 
              otherwise, the DRST message corresponse to the N-COORD 
              Response and N-COORD Confirm primitives. The Affected 
              Point Code can only contain one point code when SSN is 
              present. 
 
3.5 Application Server Process State Maintenance Messages 
 
3.5.1 ASP Up (UP) 
    
   The ASP UP (UP) message is used to indicate to a remote SUA peer 
   that the Adaptation layer is up and running. 

 
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       0                     1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |           Tag = 0x0011        |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                        ASP Identifier                         | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-  
      |            Tag = 0x0109       |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                          Info String                          /                                                                               
\                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     ASP Identifier                Optional *1 
     Info String                   Optional 
    
   Note 1:  ASP Identifier MUST be used where the IPSP/SGP cannot 
            identify the ASP by pre-configured address/port number 
            information (e.g., where an ASP is resident on a Host using 
            dynamic address/port number assignment).   
    
3.5.2 ASP Up Ack (UP ACK) 
    
   The ASP UP Ack message is used to acknowledge an ASP-Up message 
   received from a remote SUA peer. 
    
       0                     1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |            Tag = 0x0004       |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                          Info String                          /                                                                               
\                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     Info String              Optional 
    
3.5.3 ASP Down (DOWN) 
    
   The ASP Down (DOWN) message is used to indicate to a remote SUA peer 
   that the adaptation layer is not running. 

 
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       0                     1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |           Tag = 0x0004        |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                          Info String                          /                                                                               
\                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     Info String         Optional 
    
3.5.4 ASP Down Ack (DOWN ACK) 
    
   The ASP DOWN Ack message is used to acknowledge an ASP-Down message 
   received from a remote SUA peer. 
    
       0                     1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |           Tag = 0x0004        |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                          Info String                          /                                                                               
\                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     Info String         Optional 
    
   Note: ASP DOWN ACK will always be sent to acknowledge an ASP DOWN.   
    
3.5.5 Heartbeat (BEAT) 
    
   The Heartbeat message is optionally used to ensure that the SUA 
   peers are still available to each other.  
    
   The format for the BEAT message is as follows: 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |           Tag = 0x0009        |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Heartbeat Data                          / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
    
   Parameters 
     Heartbeat Data      Optional 
    

 
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3.5.6 Heartbeat Ack (BEAT ACK) 
    
   The Heartbeat ACK message is sent in response to a BEAT message. A 
   peer MUST send a BEAT ACK in response to a BEAT message. It includes 
   all the parameters of the received Heartbeat message, without any 
   change. 
    
   The format for the BEAT ACK message is as follows: 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |           Tag = 0x0009        |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Heartbeat Data                          / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
    
   Parameters 
     Heartbeat Data      Optional 
    
3.6 ASP Traffic Maintenance Messages 
    
3.6.1 ASP Active (ACTIVE) 
    
   The ASPAC message is sent by an ASP to indicate to a remote SUA peer 
   that it is Active and ready to process signalling traffic for a 
   particular Application Server. 
    
   The format for the ACTIVE message is as follows: 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |           Tag = 0x000B        |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |                       Traffic Mode Type                       | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |           Tag = 0x0006        |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |          Tag = 0x0119         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                           TID Label                           | 
      +-------------------------------+-------------------------------+ 
      |          Tag = 0x0118         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                           DRN Label                           | 
      +-------------------------------+-------------------------------+ 
      |           Tag = 0x0004        |             Length            | 
 
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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                          Info String                          / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     Traffic Mode Type   Optional 
     Routing Context     Optional 
     TID Label           Optional 
     DRN Label           Optional 
     Info String         Optional 
    
3.6.2 ASP Active Ack (ACTIVE ACK) 
    
   The ASPAC Ack message is used to acknowledge an ASP-Active message  
   received from a remote SUA peer. 
    
   The format for the ACTIVE Ack message is as follows: 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |           Tag = 0x000B        |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |                       Traffic Mode Type                       | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |           Tag = 0x0006        |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |          Tag = 0x0004         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                          Info String                          / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     Traffic Mode Type   Optional 
     Routing Context     Optional 
     Info String         Optional 
    
   The value of the Traffic Mode Type and Routing Context parameters is 
   the same as for the ASP-Active message. 
    
   The value of the optional Info String parameter is the same as for 
   the ASP-Active message. 
    
3.6.3 ASP Inactive (INACTIVE) 
    

 
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   The INACTIVE message is sent by an ASP to indicate to a remote SUA 
   peer that it is no longer processing signalling traffic within a 
   particular Application Server.   
    
   The format for the ASPIA message parameters is as follows: 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |           Tag = 0x0006        |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |           Tag = 0x0004        |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                          INFO String                          / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     Routing Context     Optional 
     INFO String         Optional 
    
3.6.4 ASP Inactive Ack (INACTIVE ACK) 
    
   The INACTIVE Ack message is used to acknowledge an ASP-Inactive 
   message received from a remote SUA peer. 
    
   The format for the INACTIVE Ack message is as follows: 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x0006         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |          Tag = 0x0004         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                          INFO String                          / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     Routing Context     Optional 
     INFO String         Optional 
    
   The value of the optional Info String parameter is the same as for 
   the ASP-Active message. 
    
 
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3.7 SUA Management Messages  
 
   These messages are used for managing SUA and the representations of 
   the SCCP subsystems in the SUA layer. 
 
3.7.1 Error (ERR) 
    
   The ERR message is sent between two SUA peers to indicate an error 
   situation. The Data parameter is optional, possibly used for error 
   logging and/or debugging. 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |          Tag = 0x000C         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                          Error Code                           | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x0007         |             Length            |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      /                        Diagnostic Info                        / 
      \                                                               \  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
    
   Parameters 
     Error Code                    Mandatory  
     Diagnostic Info               Optional 
           
3.7.2 Notify (NTFY) 
    
   The Notify message used to provide an autonomous indication of SUA 
   events to an SUA peer.   
    
       0                     1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |          Tag = 0x000D         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                           Status                              | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |            Tag = 0x0011       |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                        ASP Identifier                         | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-  
      |          Tag = 0x0006         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x0004         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                          Info String                          / 
 
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                                                                               \                                                               
\
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   The NTFY message contains the following parameters: 
    
   Parameters 
     Status                        Mandatory 
     ASP Identifier                Optional *1 
     Routing Context               Optional 
     Info String                   Optional 
    
   Note 1:  ASP Identifier MUST be used where the IPSP/SGP cannot 
            identify the ASP by pre-configured address/port number 
            information (e.g., where an ASP is resident on a Host using 
            dynamic address/port number assignment).   
    
3.8 Routing Key Management (RKM) Messages 
    
3.8.1 Registration Request (REG REQ) 
    
   The REG REQ message is sent by an ASP to indicate to a remote SUA 
   peer that it wishes to register one or more given Routing Keys with 
   the remote peer.  Typically, an ASP would send this message to an 
   SGP, and expects to receive a REG RSP message in return with an 
   associated Routing Context value. 
    
   The format for the REG REQ message is as follows: 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x010D         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                       Network Appearance                      | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x010E         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                         Routing Key 1                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                              ...                              / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x010E         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      \                                                               \ 
      /                         Routing Key n                         / 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |            Tag = 0x0109       |             Length            |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |                        ASP Capabilities                       |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
 
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   The REG REQ message contains the following parameters: 
    
   Parameters 
     Network Appearance            Optional 
     Routing Key                   Mandatory *1 
     ASP Capabilities              Optional 
    
   Note 1: One or more Routing Key parameters MAY be included in a 
           single REG REQ message. 
    
3.8.2 Registration Response (REG RSP) 
    
   The REG RSP message is sent by an SG to an ASP indicate the result 
   of a previous REG REQ from an ASP.  When successful, the REG RSP 
   message contains the Routing Context assigned to the one or more 
   Routing Keys that we present in t 
    
   The format for the REG RSP message is as follows: 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x010D         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                       Network Appearance                      | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x010F         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                    Registration Result 1                      | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                              ...                              / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x010F         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                    Registration Result n                      | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   The REG RSP message contains the following parameters: 
    
   Parameters 
     Network Appearance            Optional 
     Registration Result           Mandatory *1 
    
   Note 1: One or more Registration Result parameters MAY be included 
           in a single REG RSP message. 
    
3.8.3 Deregistration Request (DEREG REQ) 
    

 
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   The DEREG REQ message is sent by an ASP to indicate to a remote SUA 
   peer that it wishes to deregister a given Routing Key.  Typically, 
   an ASP would send this message to an SGP, and expects to receive a 
   DEREG RSP message in return with the associated Routing Context 
   value. 
    
   The format for the DEREG REQ message is as follows: 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0006            |           Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         /  
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   The DEREG REQ message contains the following parameters: 
    
   Parameters 
     Routing Context               Mandatory 
    
3.8.4 Deregistration Response (DEREG RSP) 
    
   The DEREG RSP message is used as a response to the DEREG REQ message 
   from a remote SUA peer. 
    
   The format for the DEREG RSP message is as follows: 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x0110         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                   Deregistration Result 1                     | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                              ...                              / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x0110         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                   Deregistration Result n                     | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   The DEREG RSP message contains the following parameters: 
    
   Parameters 
     Deregistration Result         Mandatory *1 
    
   Note 1:  One or more Deregistration Result parameters MAY be included 
           in one DEREG RSP message. 
    
 
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3.9 Common Parameters 
    
   These TLV parameters are common across the different adaptation 
   layers. 
    
   Parameter Name                     Parameter ID 
   ==============                     ============ 
   Reserved                             0x0000 
   Not used in SUA                      0x0001 
   Not used in SUA                      0x0002 
   Not used in SUA                      0x0003 
   Info String                          0x0004  
   Not used in SUA                      0x0005 
   Routing Context                      0x0006 
   Diagnostic Info                      0x0007 
   Not used in SUA                      0x0008 
   Heartbeat Data                       0x0009 
   Not Used in SUA                      0x000A 
   Traffic Mode Type                    0x000B 
   Error Code                           0x000C 
   Status                               0x000D 
   Not used in SUA                      0x000E 
   Congestion Level                     0x000F 
   Not used in SUA                      0x0010 
   ASP Identifier                       0x0011 
   Affected Point Code                  0x0012 
   Correlation ID                       0x0013 
    
3.9.1 Not Used  
    
   Use of Parameter ID 0x0001 in SUA messages is not supported. 
    
3.9.2 Not Used 
      
   Use of Parameter ID 0x0002 in SUA messages is not supported. 
    
3.9.3 Not Used 
 
   Use of Parameter ID 0x0002 in SUA messages is not supported. 
    
3.9.4 Info String  
    
   The INFO String parameter can carry any meaningful 8-BIT ASCII 
   character string along with the message.  Length of the INFO String 
   parameter is from 0 to 255 characters.  No procedures are presently 
   identified for its use but service providers may use the INFO String 
   for debugging purposes. 

 
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       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x0004         |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                          Info String                          /                                                                               
\                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
3.9.5 Not Used in SUA 
    
   Use of Parameter ID 0x0005 in SUA messages is not supported. 
    
3.9.6 Routing Context 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x0006         |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Routing Context                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   The Routing Context parameter contains (a list of) 4-byte unsigned 
   integers indexing the Application Server traffic that the sending 
   ASP is configured/registered to receive.  There is a one-to-one 
   relationship between an index entry and a Routing Key or AS Name.   
    
   An Application Server Process may be configured to process traffic 
   for more than one logical Application Server.  From the perspective 
   of an ASP, a Routing Context defines a range of signalling traffic 
   that the ASP is currently configured to receive from the SG.   
    
   Additionally, the Routing Context parameter identifies the SS7 
   network context for the message, for the purposes of logically 
   separating the signalling traffic between the SGP and the 
   Application Server Process over a common SCTP Association, when 
   needed.  An example is where an SGP is logically partitioned to 
   appear as an element in several different national SS7 networks.  It 
   implicitly defines the SS7 Point Code format used, the SS7 Network 
   Indicator value and SCCP protocol type/variant/version used within a 
   separate SS7 network. It also defines the network context for the PC 
   and SSN values. Where an SGP operates in the context of a single SS7 
   network, or individual SCTP associations are dedicated to each SS7 
   network context, this functionality is not needed. 
    
   If the Routing Context parameter is present, it SHOULD be the first 
   parameter in the message as it defines the format and/or 
   interpretation of the parameters containing a PC or SSN value. 
    
 
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3.9.7 Diagnostic Information 
    
   The Diagnostic Information can be used to convey any information 
   relevant to an error condition, to assist in the identification of 
   the error condition.  In the case of an Adaptation Layer Identifier 
   or Traffic Handling Mode, the Diagnostic Information includes the 
   received parameter.  In the other cases, the Diagnostic information 
   may be the first 40 bytes of the offending message. 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0007          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                     Diagnostic Information                    / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
3.9.8 Not Used 
    
   Parameter ID 0x0008 is not used in SUA. 
    
3.9.9 Heartbeat Data 
    
   The sending node defines the Heartbeat Data field contents. It may 
   include a Heartbeat Sequence Number and/or Timestamp, or other 
   implementation specific details. 
    
   The receiver of a Heartbeat message does not process this field as 
   it is only of significance to the sender.  The receiver echoes the 
   content of the Heartbeat Data in a BEAT-Ack message. 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |         Tag = 0x0009          |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Heartbeat Data                          / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
    
   The data field can be used to store information in the heartbeat 
   message useful to the sending node (e.g. the data field can contain 
   a time stamp, a sequence number, etc.). 
    
3.9.10 Not Used 
    
   Parameter ID 0x000A is not used in SUA. 
    
3.9.11 Traffic Mode Type 
 

 
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   The Traffic Mode Type parameter identifies the traffic mode of 
   operation of the ASP within an AS.  
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |          Tag = 0x000B         |             Length = 8        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                      Traffic Mode Type                        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   The valid values for Type are shown in the following table. 
    
               1         Over-ride 
               2         Load-share 
               3         Broadcast 
    
   Within a Routing Context, Over-ride, Loadshare Types and Broadcast 
   cannot be mixed.  The Over-ride value indicates that the ASP is 
   operating in Over-ride mode, and the ASP wishes to take over all 
   traffic for an Application Server (i.e., primary/back-up operation), 
   over-riding any currently active ASP in the AS.  In Load-share mode, 
   the ASP wishes to share in the traffic distribution with any other 
   currently active ASPs.  In Broadcast mode, the ASP wishes to receive 
   the same traffic as any other currently active APSs. When there are 
   insufficient ASPs, the sender may immediately move the ASP to 
   Active. 
 
3.9.12 Error Code 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |        Tag =0x000C            |             Length = 8        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                          Error Code                           | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   The Error Code parameter indicates the reason for the Error Message.  
   The Error parameter value can be one of the following values: 
    
       Error Code                                      Value 
       ===================================================== 
       Invalid Version                                 0x01 
       Invalid Interface Identifier                    0x02   
       Unsupported Message Class                                                                
0x03 
       Unsupported Message Type                        0x04   
       Unsupported Traffic Handling Mode               0x05 
       Unexpected Message                              0x06   
       Protocol Error                                  0x07 
       Unsupported Interface Identifier Type           0x08 * 
       Invalid Stream Identifier                       0x09   
 
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       Unassigned TEI                                  0x0a * 
       Unrecognized SAPI                               0x0b * 
       Invalid TEI, SAPI combination                   0x0c * 
       Refused - Management Blocking                   0x0d   
       ASP Identifier Required                         0x0e   
       Invalid ASP Identifier                          0x0f  
       Invalid Routing Context                         0x10 
       Invalid Parameter Value                         0x11   
       Parameter Field Error                           0x12 
       Unexpected Parameter                            0x13 
       Destination Status Unknown                      0x14 
       Invalid Network Appearance                      0x15 
       Missing Parameter                                                         
0x16 
       Routing Key Change Refused                      0x17 
       Invalid loadsharing Label                       0x18 
    
   Please note that values marked with * are not directly supported by 
   SUA, but are used by other User Adaptation Layers (IUA, M2UA, M3UA, 
   etc.). 
         
   The "Invalid Version" error would be sent if a message was received 
   with an invalid or unsupported version.  The Error message would 
   contain the supported version in the Common header.  The Error 
   message could optionally provide the supported version in the 
   Diagnostic Information area. 
    
   The "Invalid Routing Context" error would be sent by a SG if an ASP 
   sends a message with an invalid (unconfigured) Routing Context 
   value.  The Error message could optionally provide the invalid 
   Routing Context in the Diagnostic Information area. 
    
   The "Unexpected Message Class" error would be sent if a message with 
   an unsupported Message Class were received. 
    
   The "Unexpected Message Type" error would be sent if a message with 
   an unsupported Message Type were received. 
    
   The "Unsupported Traffic Handling Mode" error would be sent by a SGP 
   if an ASP sends an ASP Active with an unsupported Traffic Handling 
   Mode.  An example would be a case in which the SGP did not support 
   load sharing. 
    
   The "Unexpected Message" error MAY be sent if a defined and 
   recognized message is received that is not expected in the current 
   state (in some cases the ASP may optionally silently discard the 
   message and not send an Error message).  For example, silent discard 
   is used by an ASP if it received a DATA message from an SGP while it 
   was in the ASP-INACTIVE state.  
    
   The "Protocol Error" error would be sent for any protocol anomaly 
   (i.e., reception of a parameter that is syntactically correct but 
   unexpected in the current situation. 
 
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   The "Invalid Routing Context" error is sent if a message is received 
   from a peer with an invalid (unconfigured) Routing Context value, or 
   if a message is received from a peer without a Routing Context 
   parameter and it is not known by configuration data which 
   Application Servers are referenced. 
    
   The "Invalid Stream Identifier" error is sent if a message is 
   received on an unexpected SCTP stream (e.g., a Management message 
   was received on a stream other than "0", or a Data message was 
   received on stream "0"). 
    
   The "Parameter Field Error" would be sent if a message is received 
   with a parameter having a wrong length field. 
    
   The "Unexpected Parameter" error would be sent if a message contains 
   a parameter not defined within a message. 
    
   The "Invalid Parameter" error would be sent if a message contains an 
   invalid parameter, for example a parameter having a value outside of 
   the acceptable range of values. 
     
   The "ASP Identifier Required" is sent by a SGP in response to an ASP 
   Up message, which does not contain an ASP Identifier parameter when 
   the SGP requires one.  The ASP should resend the ASP Up message with 
   an ASP Identifier. 
    
   The "Invalid ASP Identifier" is send by a SGP in response to an ASP 
   Up message with an invalid (i.e., non-unique) ASP Identifier. 
    
   The "Destination Status Unknown" Error MAY be sent if a DAUD is 
   received at an SG enquiring of the availability/congestion status of 
   a destination, and the SG does not wish to provide the status (e.g., 
   the sender is not authorized to know the status). 
    
   The "Missing Parameter" error would be sent if a mandatory parameter 
   were not included in a message. 
    
   The "Routing Key Change Refused" error is sent when the SG refuses a 
   change in the Routing Key parameters.   
    
3.9.13 Status  
    
   The Status parameter identifies the type of the status that is being 
   notified and the Status ID. 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |          Tag = 0x000D         |             Length = 8        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Status Type           |            Status ID          | 
 
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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   The valid values for Status Type (16 bit unsigned integer) are: 
    
          1     Application Server state change (AS_State_Change) 
          2     Other  
    
   The Status ID parameter contains more detailed information for the 
   notification, based on the value of the Status Type. 
    
   If the Status Type is AS_STATE_CHANGE, then the Status ID (16 bit 
   unsigned integer) values are: 
    
          1    reserved 
          2    Application Server Inactive (AS-Inactive) 
          3    Application Server Active (AS-Active) 
          4    Application Server Pending (AS-Pending) 
    
    
   These notifications are sent from an SGP to an ASP upon a change in 
   status of a particular Application Server. The value reflects the 
   new state of the Application Server. 
    
   If the Status Type is "Other", then the following Status Information 
   values are defined: 
    
          1    Insufficient ASP resources active in AS 
          2    Alternate ASP Active 
          3    ASP failure 
              
   These notifications are not based on the SGP reporting the state 
   change of an ASP or AS.  In the Insufficient ASP Resources case, the 
   SGP is indicating to an "Inactive" ASP(s) in the AS that another ASP 
   is required to handle the load of the AS (Load-sharing mode or 
   Broadcast mode).  For the Alternate ASP Active case, an ASP is 
   informed when an alternate ASP transitions to the ASP-Active state 
   in Over-ride mode.   
    
3.9.14 Not Used in SUA 
    
   Parameter ID 0x000E is not used in SUA. 
    
3.9.15 Congestion Level 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x000F          |             Length = 8        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                       Congestion Level                        |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
       
 
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   Congestion Level field: 8-bits (unsigned integer) 
    
   The valid values for the Congestion Level parameter range from 0 to 
   7, where 0 indicates least congested and 7 indicates most congested 
   subsystem. 
    
3.9.16 Not Used in SUA 
    
   Parameter ID 0x0010 is not used in SUA. 
 
3.9.17 ASP Identifier 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0011          |             Length = 8        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                        ASP Identifier                         | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   ASP Identifier field: 32-bits (unsigned integer) 
    
   The ASP Identifier field contains a unique value that is locally 
   significant amoung the ASPs that support an AS.  The SGP should save 
   the ASP Identifier to be used, if necessary, with the Notify message 
   (see Section 3.7.2).   
    
   The optional ASP Identifier parameter would contain a unique value  
   that is locally significant among the ASPs that support an AS.  The  
   SGP should save the ASP Identifier to be used, if necessary, with 
   the Notify message (see Section 3.3.3.2). 
    
3.9.18 Affected Point Code 
    
   The Affected Point Code Destinations parameter contains up to 
   sixteen Affected Point Code fields, each a three-octet parameter to 
   allow for 14-, 16- and 24-bit binary formatted SS7 Point Codes.  
   Affected Point Codes that are less than 24-bits are padded on the 
   left to the 24-bit boundary.   
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x0012         |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |    Mask       |                 Affected PC 1                 | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                             . . .                             / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   The encoding is shown below for ANSI and ITU Point Code examples. 
 
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   ANSI 24-bit Point Code: 
    
       0                   1                   2                   3--> 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |     Mask      |    Network    |    Cluster    |     Member    | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
                      |MSB-----------------------------------------LSB| 
    
   ITU 14-bit Point Code: 
    
       0                   1                   2                   3--> 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |     Mask      |0 0 0 0 0 0 0 0 0 0|Zone |     Region    | SP  | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
                                           |MSB--------------------LSB| 
    
   It is optional to send an Affected Point Code parameter with more 
   than one Affected PC but it is mandatory to receive it.  All the 
   Affected PCs included MUST be within the same Routing Context.  
   Including multiple Affected PCs may be useful when reception of a 
   management message or a linkset event simultaneously affects the 
   availability status of a list of destinations at an SG.   
    
   Mask: 8-bits 
    
   The Mask parameter can be used to identify a contiguous range of 
   Affected Destination Point Codes, independent of the point code 
   format.  Identifying a contiguous range of Affected PCs may be 
   useful when reception of an MTP3 management message or a linkset 
   event simultaneously affects the availability status of a series of 
   destinations at an SG.  
    
   The Mask parameter is an integer representing a bit mask that can be 
   applied to the related Affected PC field.  The bit mask identifies 
   how many bits of the Affected PC field are significant and which are 
   effectively "wild-carded".  For example, a mask of "8" indicates 
   that the last eight bits of the PC is "wild-carded".  For an ANSI 
   24-bit Affected PC, this is equivalent to signalling that all PCs in 
   an ANSI Cluster are unavailable.  A mask of "3" indicates that the 
   last three bits of the PC is "wild-carded".  For a 14-bit ITU 
   Affected PC, this is equivalent to signalling that an ITU Region is 
   unavailable. 
    
3.9.19 Correlation ID 
    
     0                   1                   2                   3  
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1  
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
    |          Tag = 0x0013         |             Length = 8        |  
 
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    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
    |                        Correlation ID                         |  
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
         
   The Correlation ID is a 32-bit identifier that is attached to CLDT 
   messages to indicate to a newly entering ASP in a Broadcast AS where 
   in the traffic flow of CLDT messages the ASP is joining.  It is 
   attached to the first CLDT message sent to an ASP by an SG after 
   sending an ASP Active Ack or otherwise starting traffic to an ASP.  
   The Correlation ID is only significant within a Routing Context.   
    
   Implementation note: Correlation ID parameter can be use for 
   features like Synchronisation of ASPs/SGPs in a Broadcast Mode 
   AS/SG; avoid message duplication and mis-sequencing in case of 
   failover of association from one ASP/SGP to other ASP/SGP etc. 
    
3.10 SUA-Specific parameters  
    
   These TLV parameters are specific to the SUA protocol. 
 
   Parameter Name                     Parameter ID 
   ==============                     ============ 
   SS7 Hop Counter                      0x0101 
   Source Address                       0x0102 
   Destination Address                  0x0103 
   Source Reference Number              0x0104 
   Destination Reference Number         0x0105 
   SCCP Cause                           0x0106 
   Sequence Number                      0x0107 
   Receive Sequence Number              0x0108 
   ASP Capabilities                     0x0109 
   Credit                               0x010A 
   Data                                 0x010B 
   User/Cause                           0x010C 
   Network Appearance                   0x010D 
   Routing Key                          0x010E 
   Registration Result                  0x010F 
   Deregistration Result                0x0110 
   Address Range                        0x0111 
   SMI                                  0x0112 
   Importance                           0x0113 
   Message Priority                     0x0114 
   Protocol Class                       0x0115 
   Sequence Control                     0x0116 
   Segmentation                         0x0117 
   DRN Label                            0x0118 
   TID Label                            0x0119 
    
   Destination/Source Address Sub-Parameters 
   =========================================== 
   Global Title                         0x8001  
   Point Code                           0x8002 
 
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   Subsystem Number                     0x8003 
   IPv4 Address                         0x8004 
   Hostname                             0x8005           
   IPv6 Addresses                       0x8006 
    
3.10.1 SS7 Hop counter  
    
      0                   1                   2                   3 
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |         Tag = 0x0101          |             Length = 8        | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |              Reserved                         | SS7 Hop Count |   
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   SS7 Hop Counter (3.18/Q.713) 
    
   The value of the SS7 Hop Counter is decremented with each global 
   title translation and is in the range 15 to 1.  
    
3.10.2 Source Address  
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |          Tag = 0x0102         |      Parameter Length         |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |      Routing Indicator        |       Address Indicator       | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      /                       Address parameter(s)                    /  
      \                                                               \  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
    
   The following combinations of address parameters are valid: 
    
     -    Global Title (e.g. E.164 number) + optional PC and/or SSN, 
          SSN may be zero, when routing is done on Global Title 
     -    SSN (non-zero) + optional PC and/or Global Title, when 
          routing is done on PC + SSN. The PC is mandatory in the 
          source address when sending from SGP to ASP, and in the 
          destination address when sending from ASP to SGP to reach the 
          SS7 SEP. 
     -    Hostname + optional SSN, when routing is done by Hostname 
     -    SSN (non-zero) and optional IP address (IPv4 or IPv6) when 
          routing is done on IP address + SSN 

3.10.2.1 Routing Indicator 
    
   The following values are valid for the routing indicator: 
    
     Reserved                      0 
 
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     Route on Global Title         1 
     Route on SSN + PC             2 
     Route on Hostname             3 
     Route on SSN + IP Address     4 
    
   The routing indicator determines which address parameters need to be 
   present in the address parameters field. 
    
3.10.2.2 Address Indicator 
 
   This parameter is needed for interworking with SS7 networks. The 
   address indicator specifies what address parameters are actually 
   received in the SCCP address from the SS7 network, or are to be 
   populated in the SCCP address when the message is sent into the SS7 
   network. The value of the routing indicator needs to be taken into 
   account.  It is used in the ASP to SG direction.  For example, the 
   PC parameter is present in the destination address of the CLDT sent 
   from ASP->SG, but bit 2 is set to "0" meaning "do not populate this 
   in the SCCP called party address". The effect is that the SG only 
   uses the PC to populate the MTP routing label DPC field, but does 
   not include it in the SCCP called party address. 
    
   In the SG->ASP direction, the source address PC parameter is present 
   (PC of SS7 SEP). However, this may have been populated from the OPC 
   in the received MTP routing label, not from the PC field in the SCCP 
   calling party address. In this case, bit 2 = "0" denotes that. The 
   AI gives further instructions to the SG how and when to populate the 
   SCCP addresses; in the SG->ASP direction, the AI gives information 
   to the ASP as to what was actually present in the received SCCP 
   addresses. 
    
   The address indicator is coded as follows: 
    
    Bit 1 is used to indicate inclusion of the SSN 
    
    0         Do not include SSN when optional 
     1         Include SSN 
    
     Bit 2 is used to indicate inclusion of the PC 
    
    0         Do not include PC, regardless of the routing indicator 
              value 
     1        Include PC 
    
    Bit 3 is used to indicate inclusion of the Global Title 
    
    0         Do not include GT when optional (routing indicator /= 1) 
     1        Include GT 
    
   The remaining bits are spare and SHOULD be coded zero, and MUST be 
   ignored by the receiver. 

 
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3.10.2.3 Global Title 
      
     0                   1                   2                   3 
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1  
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |         Tag = 0x8001          |            Length             | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |   No. Digits  | Trans. type   |    Num. Plan  | Nature of Add | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     /                         Global Title Digits                   / 
     \                                                               \ 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Length: 
    
   Does not include the filler bits. 
    
   Number of Digits: 
    
   This is the number of digits contained in the Global Title. 
    
   Translation type: 
    
     0              Unknown 
     1 - 63         International services 
     64 - 127       Spare 
     128 “ 254      National network specific 
     255            Reserved 
    
   Numbering Plan: 
    
     0         unknown 
     1         ISDN/telephony numbering plan (Recommendations E.163 and 
               E.164) 
     2         generic numbering plan 
     3         data numbering plan (Recommendation X.121) 
     4         telex numbering plan (Recommendation F.69) 
     5         maritime mobile numbering plan (Recommendations E.210, 
               E.211) 
     6         land mobile numbering plan (Recommendation E.212) 
     7         ISDN/mobile numbering plan (Recommendation E.214) 
     8 - 13    spare 
     14        private network or network-specific numbering plan 
     15 - 126  spare 
     127       reserved. 
    
   Nature of Address: 
    
     0         unknown 
     1         subscriber number 
     2         reserved for national use 
 
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     3         national significant number 
     4         international number 
     5 - 255   Spare 
    
   Global Title: 
    
    Octets contain a number of address signals and possibly filler as 
    shown: 
    
      0                   1                   2                   3 
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |2 addr.|1 addr.|4 addr.|3 addr.|6 addr.|5 addr.|8 addr.|7 addr.| 
     |  sig. | sig.  |  sig. | sig.  |  sig. | sig.  |  sig. | sig.  | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |        .............          |filler |N addr.|   filler      | 
     |                               |if req | sig.  |               | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   All filler bits SHOULD be set to 0. 
    
   Address signals to be coded as defined in ITU-T Q.713 Section 
   3.4.2.3.1. 
    
   The actual Global Title format to be used for interworking with the 
   SS7 network is defined by the network ID, or is implicitly 
   understood if the SGP only operates in one SS7 network partition. 
   The formats are defined in chapter 3.4.2.3 of Q.713. The following 
   conversions of the Translation Type, Numbering Plan and Nature of 
   Address elements apply: 
    
   1) SS7 network uses GTI = 0001 
    
   Nature of Address is ignored. It is implicitly assumed that 
   Translation Type = Unknown and Numbering Plan = E.164 (value 1).  
    
   2) SS7 network uses GTI = 0010 
    
   This is most commonly used in North American networks. The 
   Translation Type implicitly determines Nature of Address and 
   Numbering Plan. This data can be configured in the SG. The number of 
   digits is always even and determined by the SCCP address length.  
    
   3) SS7 network uses GTI = 0011 
    
   Numbering Plan and Translation Type are taken over. It is implicitly 
   assumed that the Nature of Address = Unknown.  
    
   4) SS7 network uses GTI = 0100 
    

 
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   This format is used in international networks and most commonly in 
   networks outside North America. All information to populate the 
   source address is present in the SCCP Address. 
 
3.10.2.4 Point Code 
    
     0                   1                   2                   3 
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |         Tag = 0x8002          |            Length = 8         | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |                            Point Code                         | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   See chapter 3.9.18 Affected Point Code for the layout of the Point 
   Code field. 

3.10.2.5 Subsystem Number 
    
     0                   1                   2                   3 
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |         Tag = 0x8003          |            Length = 8         | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |                 Reserved                      |   SSN value   | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   The internationally standardized SSN values are described in chapter 
   3.4.2.2 of Q.713. 

3.10.2.6 IP Addresses 
    
   The IP address formats can use different tags. It should be noted 
   that if the source address is in a certain IP version, the 
   destination address should also be in the same IP version. 
    
     0                   1                   2                   3 
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |      Tag = 0x8004/0x8006      |            Length             | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     /                        IPv4 or IPv6 Address                   / 
     \                                                               \ 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Note: The tag value 0x8004 is for an IPv4 address and 0x8006 is for 
   IPv6. 
    

 
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3.10.2.7 Hostname 
    
     0                   1                   2                   3 
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |         Tag = 0x8005          |            Length             | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     /                           Host Name                           / 
     \                                                               \ 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Host Name: variable length 
    
   This field contains a host name in "host name syntax" per RFC 1123       
   Section 2.1 [1123].  The method for resolving the host name is       
   out of scope for this document. 
    
   Note: At least one null terminator is included in the Host Name 
        string and must be included in the length. 
      
3.10.3 Destination Address 
    
      0                   1                   2                   3  
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |          Tag = 0x0103         |      Parameter Length         | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |      Routing Indicator        |       Address Indicator       | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     /                       Address Parameter(s)                    / 
     \                                                               \ 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   The format of this parameter is identical to the Source Address 
   parameter. 
 
3.10.4 Source Reference Number 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x0104         |             Length = 8        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                   Source Reference Number                     | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   The source reference number is a 4 octet long integer. This is 
   allocated by the source SUA instance. 
 
3.10.5 Destination Reference Number 
    

 
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       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x0105         |             Length = 8        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                 Destination Reference Number                  | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   The destination reference number is a 4 octet long integer. This is 
   allocated by the destination SUA instance. 
    
3.10.6 SCCP Cause 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0106          |             Length = 8        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Reserved              |   Cause Type  |  Cause Value  | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   This parameter bundles the SCCP parameters Release cause, Return 
   cause, Reset cause, Error cause and Refusal cause. 
    
   Cause Type can have the following values: 
    
        Return Cause          0x1 
        Refusal Cause         0x2 
        Release Cause         0x3 
        Reset Cause           0x4 
        Error Cause           0x5 
    
   Cause Value contains the specific cause value.  Below gives examples 
   for ITU SCCP values.  ANSI references can be found in ANSI T1.112.3 
    
   Cause value in        Correspondence with Reference 
   SUA message           SCCP parameter  
   ------------------    -----------------   --------- 
   CLDR                  Return Cause        ITU-T Q.713 Chap 3.12 
   COREF                 Refusal Cause       ITU-T Q.713 Chap 3.15 
   RELRE                 Release Cause       ITU-T Q.713 Chap 3.11 
   RESRE                 Reset Cause         ITU-T Q.713 Chap 3.13 
   ERR                   Error Cause         ITU-T Q.713 Chap 3.14  
    
3.10.7 Sequence Number 
    

 
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       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x0107         |             Length = 8        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Reserved              |  Rec Seq Num|M| Sent Seq Num  | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   This parameter is used to indicate whether "more" data will follow 
   in subsequent CODT messages, and/or to number each CODT message 
   sequentially for the purpose of flow control. It contains the 
   received as well as the sent sequence number, P(R) and P(S) in 
   Q.713, chapters 3.7 and 3.9.  
    
   As such it can also be used to acknowledge the receipt of data 
   transfers from the peer in case of protocol class 3. 
    
   Sent Sequence Number is one octet and is coded as follows: 
    
          Bits 2-8 are used to indicate the Send Sequence Number P(S). 
          Bit 1 (LSB) of octet 1 is spare. 
    
   Received Sequence Number is one octet, and is coded as follows: 
    
          Bits 2-8 are used to indicate the Received Sequence Number  
          P(R). 
          Bit 1 (LSB) is used for the more data indication, as follows: 
           
          0         no more data 
          1         more data 
    
3.10.8 Receive Sequence Number 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x0108         |             Length = 8        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                    Reserved                   |  Rec Seq Num  | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   This parameter is used exclusively for protocol class 3 in the data 
   acknowledgment message to indicate the lower edge of the receiving 
   window. See Q.713, chapter 3.9. 
    
   It is a 1 octet long integer coded as follows: 
    
      Bits 8-2 are used to indicate the Receive Sequence Number P(R). 
    
      Bit 1 is spare. 
    

 
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3.10.9 ASP Capabilities 
    
   This parameter is used so that the ASP can report its capabilities 
   regarding SUA for supporting different protocol classes and  
   interworking scenarios.  
        
       0                   1                   2                   3  
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+       
      |          Tag = 0x0109         |             Length = 8        |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |         Reserved              |0 0 0 0|a|b|c|d| Interworking  |  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
        
      Flags  
        
        a - Protocol Class 3  
        b - Protocol Class 2  
        c - Protocol Class 1  
        d - Protocol Class 0  
        
        It is mandatory to support at least Protocol Class 0.  
        
   Interworking   
        
    Values  
       
      0x0 indicates no interworking with SS7 Networks.  
      0x1 indicates IP Signalling Endpoint (ASP), interworking with SS7 
         networks. 
      0x2 indicates Signalling Gateway.  
      0x3 indicates relay node support.   
        
3.10.10 Credit 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |          Tag = 0x010A         |             Length = 8        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                 Reserverd                     |     Credit    | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   The length of the credit field is is one octet.  See ITU-T Q.713  
   Chapter 3.10. The parameter is used for protocol class 3 
   exclusively. 
    
3.10.11 Data 
 
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
 
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      |          Tag = 0x010b         |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                             Data                              / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   The Data parameter field contains the SS7 SCCP-User application 
   message, for example an INAP/TCAP message. 
    
3.10.12 Cause / User 

 
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      0                   1                   2                   3 
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |         Tag = 0x010c          |             Length = 32       | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |             Cause             |            User               | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   "User" is coded to that SCCP's SI value.  There may be several 
   SCCP's at a given point code, each with different SI values, 
   although normally there is only one with SI = 3. 
    
   Cause may take the following values 
    
     0    remote SCCP unavailable, reason unknown; 
     1    remote SCCP unequipped; 
     2    remote SCCP inaccessible; 
    
3.10.13 Network Appearance 
    
      0                   1                   2                   3 
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |         Tag = 0x010D          |             Length = 32       | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |                      Network Appearance                       | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Network Appearance field: 32-bits (unsigned integer) 
    
     The Network Appearance field identifies the SS7 network context 
     for the Routing Key.  The Network Appearance value is of local 
     significance only, coordinated between the SG and ASP. Therefore, 
     in the case where the ASP is connected to more than one SG, the 
     same SS7 Network context may be identified by different Network 
     Appearance values depending upon to which SG the ASP is 
     registering. 
      
     In the Routing Key, the Network Appearance identifies the SS7 
     Point Code and Global Title Translation Type format used, and the 
     SCCP and possibly the SCCP-User protocol (type, variant and 
     version) used within the specific SS7 network. 
      
3.10.14 Routing Key 

 
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      0                   1                   2                   3 
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |         Tag = 0x010E          |             Length            | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |                  Local Routing Key Identifier                 | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     /                                                               / 
     \                         Key parameter(s)                      \ 
     /                                                               / 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Local Routing Key Identifier field: 32-bits (unsigned integer) 
      
     The Local Routing Key Identifier field is used to uniquely 
     identify the registration request.  The Identifier value is 
     assigned by the ASP and is used to correlate the response in a REG 
     RSP message with the original registration request. The Identifier 
     value must remain unique until the REG RSP message is received. 
    
   Key field: variable 
    
   The Key field contains the following parameters: 
    
        Parameter 
           Traffic Mode Type          Optional 
           Network Appearance         Optional *1 
           Source Address             Optional 
           Destination Address        Optional 
           Address Range              Optional 
    
   Note 1: The Network Appearance parameter must be included in the 
           Routing Key when the ASP is able to register in                                                                     
           multiple SS7 Network contexts. 
    
3.10.15 Registration Result 
    
      0                   1                   2                   3 
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |         Tag = 0x010F          |             Length            | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |                  Local Routing Key Identifier                 | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |                       Registration Status                     | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |                         Routing Context                       | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Local Routing Key Identifier field: 32-bit (unsigned integer) 
    
 
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     The Local Routing Key Identifier field contains the same value as 
     found in the matching Routing Key parameter in the REG REQ 
     message. 
    
   Registration Status: 32-bits (unsigned integer) 
    
     The Registration Status field indicates the success or the reason 
     for failure of a registration request. 
      
     Its values may be: 
             0           Successfully Registered 
             1           Error - Unknown 
             2           Error - Invalid Destination Address 
             3           Error - Invalid Network Appearance 
             4           Error - Invalid Routing Key 
             5           Error - Permission Denied 
             6           Error - Cannot Support Unique Routing 
             7           Error - Routing Key not Currently Provisioned 
             8           Error - Insufficient Resources 
             9           Error - Unsupported RK parameter Field 
            10           Error - Unsupported/Invalid Traffic Mode Type 
    
   Routing Context: 32-bits (unsigned integer) 
    
    The Routing Context field contains the Routing Context value      
    for the associated Routing Key if the registration was      
    successful.  It is set to "0" if the registration was not      
    successful. 
    
3.10.16 Deregistration Result 
    
      0                   1                   2                   3 
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |         Tag = 0x0110          |             Length            | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |                         Routing Context                       | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |                      Deregistration Status                    | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Routing Context: 32-bits (unsigned integer) 
    
     The Routing Context field contains the Routing Context value of 
     the matching Routing key to deregister, as found in the DEREG REQ 
     message. 
    
   Deregistration Status: 32-bits (unsigned integer) 
    
     The Deregistration Status field indicates the success or the 
     reason for failure of the deregistration. 
    
 
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        Its values may be: 
             0      Successfully Deregistered 
             1      Error - Unknown 
             2      Error - Invalid Routing Context 
             3      Error - Permission Denied 
             4      Error - Not Registered 
             5      Error - ASP Currently Active for Routing Context 
    
3.10.17 Address Range 
    
      0                   1                   2                   3 
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |         Tag = 0x0111          |             Length            | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     \                       Address parameter(s)                    \ 
     /                                                               / 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Address field: 
    
   The Address field the following parameters: 
    
   Parameter 
     Source Address              Optional *1 
     Destination Address         Optional *1 
    
   Note 1:  The Address field must contain pairs of Source Addresses or 
           pairs of Destination Addresses but MUST NOT mix Source 
           Addresses with Destination Addresses in the same Address 
           field. 
    
3.10.18 SMI 
 
   0                   1                   2                   3 
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
  |         Tag = 0x0112          |            Length = 8         | 
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
  |                    Reserved                  |       SMI      | 
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
 
   Subsystem Multiplicity Indicator (SMI) can have the following 
   values: 
     
   0x00       Reserved/Unknown 
   0x01       Solitary 
   0x02       Duplicated 
   0x03       Triplicated 
   0x04       Quadruplicated 
   ...        ... 
   0xff       Unspecified 
 
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3.10.19 Importance   
      
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0113          |             Length = 8        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                Reserved                       |   Importance  | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      
   Importance (3.19/Q.713) 
    
   Possible values of the Importance Parameter are between 0 and 7, 
   where the value of 0 indicates the least important and 7 indicates 
   the most important. 
    
3.10.20 Message Priority (or Priority)  
    
      0                   1                   2                   3 
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |         Tag = 0x0114          |             Length = 8        | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |              Reserved                         |  Msg Priority | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Priority 
    
   Priority value ranges from 0 to 3.  If the Priority value has not 
   been specified by the SCCP user, it should be set to 0xFF. The SG 
   MAY take the priority into account for determining the MTP message 
   priority.  In the all-IP case, this parameter MAY be used. 
    
   The Message Priority parameter is optional in the CLDT, CLDR, CORE, 
   COAK and CODT messages.  However, for networks, which support 
   Message Priority message priorities (e.g, ANSI), this parameter MUST 
   be included but it is not required for those which don't (e.g., 
   International).   
    
3.10.21 Protocol Class 
    
      0                   1                   2                   3 
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |         Tag = 0x0115          |             Length = 8        | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |              Reserved                         |  Protocol Cl. | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Protocol class (3.6/Q.713) 
    
 
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   Bits 1-2 indicate the protocol class. 
    
          Value     Description  
            0       Class 0 (connectionless service)  
            1       Class 1 (connectionless service)  
            2       Class 2 (connection-oriented service)  
            3       Class 3 (connection-oriented service) 
    
   Bit 8 indicates the use of the return on error procedure. 
    
          Value     Description  
           0x0      No special options 
           0x1      Return message on error 
    
                    Bits 3-7 are spare and SHOULD be coded zero, and MUST be 
         ignored by the receiver. 
    
3.10.22 Sequence Control 
    
      0                   1                   2                   3 
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |         Tag = 0x0116          |             Length = 8        | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |                        Sequence  Control         | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Sequence Control (1.1.2/Q.714) 
    
   The field is coded with the value of the sequence control parameter 
   associated with a group of messages and are chosen so as to ensure 
   proper loadsharing of message groups over SLS values while ensuring 
   that sequence control values within message groups have the sequence 
   control value coded with the same value as the initial message of 
   the message group. 
    
3.10.23 Segmentation 
    
      0                   1                   2                   3 
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |         Tag = 0x0117          |            Length = 32        | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     | first/remain  |             Segmentation Reference            | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   The first/remaining segments field is formatted as follows: 
   bit 8 (MSB) : indicates whether this is the first segment (1) or not 
   (0) 
    
   bits 1-7: indicate the number of remaining segments, value between 0 
   and 15 
 
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   The field would thus be coded 1000 0000 (first, no remaining 
   segments) for a non-segmented CLDT. 
    
   The segmentation reference field is a 3 byte integer, assigned by 
   the ASP. 
    
3.10.24 DRN Label 
    
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |          Tag = 0x0118         |            Length = 8         | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |     start     |      end      |         label value           | 
      +---------------+---------------+-------------------------------+ 
    
   The Start parameter is the start position of label, between 0 (LSB) 
   and 23 (MSB). 
    
   The End parameter is the end position of label, between 0 (LSB) and 
   23 (MSB). 
    
   Label value is a 16-bit interger, which is unique across an AS. 
 
3.10.25 TID Label 
    
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
      |          Tag = 0x0119         |            Length = 8         | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |     start     |      end      |         label value           | 
      +---------------+---------------+-------------------------------+ 
    
   The Start parameter is the start position of label, between 0 (LSB) 
   and 31 (MSB). 
    
   The End parameter is the end position of label, between 0 (LSB) and 
   31 (MSB). 
    
   Label value is a 16-bit interger, which is unique across an AS. 
    
4. Procedures 
    
   The SUA layer needs to respond to various local primitives it 
   receives from other layers as well as the messages that it receives 
   from the peer SUA layer.  This section describes the SUA procedures 
   in response to these events. 
    
4.1 Procedures to Support the SUA-User Layer 
    
4.1.1 Receipt of Primitives from SCCP 
    
 
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   When an SCCP Subsystem Management (SCMG) message is received from the 
   SS7 network, the SGP needs to determine whether there are concerned 
   Application Servers interested in subsystem status changes. The SUA 
   management function is informed with the N-State or N-Coord primitive 
   upon which it formats and transfers the applicable SNMM message to 
   the list of concerned ASPs using stream ID "0".     
    
   When MTP-3 Management indications are received (MTP-PAUSE, MTP-
   RESUME, MTP-STATUS), SCCP Subsystem Management determines whether 
   there are concerned local SCCP-users. When these local SCCP-users are 
   in fact Application Servers, serviced by ASPs, SUA management is 
   informed with the PC-State indication primitive upon which it formats 
   and transfers the applicable SNM message (DUNA, DAVA, DRST or SCON) 
   to the list of concerned ASPs using stream ID "0".    
        
   The SUA message distribution function determines the Application 
   Server (AS) based on comparing the information in the N-UNITDATA 
   request primitive with a provisioned Routing Key.  
    
   From the list of ASPs within the AS table, an ASP in the ASP-ACTIVE 
   state is selected and a DATA message is constructed and issued on the 
   corresponding SCTP association.  If more than one ASP is in the ASP-
   ACTIVE state (i.e., traffic is to be load-shared across more than one 
   ASP), one of the ASPs in the ASP_ACTIVE state is selected from the 
   list.  If the ASPs are in Broadcast Mode, all active ASPs will be 
   selected and the message sent to each of the active ASPs.  The 
   selection algorithm is implementation dependent but could, for 
   example, be round robin or based on the SLS.  The appropriate 
   selection algorithm must be chosen carefully as it is dependent on 
   application assumptions and understanding of the degree of state 
   coordination between the ASP_ACTIVE ASPs in the AS.  
    
   In addition, the message needs to be sent on the appropriate SCTP 
   stream, again taking care to meet the message sequencing needs of the 
   signalling application. DATA messages MUST be sent on an SCTP stream 
   other than stream '0' when there is more than one stream. 
    
   When there is no Routing Key match, or only a partial match, for an 
   incoming SS7 message, a default treatment MAY be specified.  Possible 
   solutions are to provide a default Application Server at the SGP that 
   directs all unallocated traffic to a (set of) default ASP(s), or to 
   drop the message and provide a notification to Layer Management in an 
   M-ERROR indication primitive.  The treatment of unallocated traffic 
   is implementation dependent. 
    
4.2 Receipt of Primitives from the Layer Management 
    
   On receiving primitives from the local Layer Management, the SUA 
   layer will take the requested action and provide an appropriate 
   response primitive to Layer Management. 
    

 
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   An M-SCTP_ESTABLISH request primitive from Layer Management at an ASP 
   or IPSP will initiate the establishment of an SCTP association.  The 
   SUA layer will attempt to establish an SCTP association with the 
   remote SUA peer by sending an SCTP-ASSOCIATE primitive to the local 
   SCTP layer.   
    
   When an SCTP association has been successfully established, the SCTP 
   will send an SCTP-COMMUNICATION_UP notification primitive to the 
   local SUA layer.  At the SGP or IPSP that initiated the request, the 
   SUA layer will send an M-SCTP_ESTABLISH confirm primitive to Layer 
   Management when the association setup is complete.  At the peer SUA 
   layer, an M-SCTP_ESTABLISH indication primitive is sent to Layer 
   Management upon successful completion of an incoming SCTP association 
   setup. 
    
   An M-SCTP_RELEASE request primitive from Layer Management initates 
   the shutdown of an SCTP association.  The SUA layer accomplishes a 
   graceful shutdown of the SCTP association by sending an SCTP-SHUTDOWN 
   primitive to the SCTP layer. 
    
   When the graceful shutdown of the SCTP association has been 
   accomplished, the SCTP layer returns an SCTP-SHUTDOWN_COMPLETE 
   notification primitive to the local SUA layer.  At the SUA Layer that 
   initiated the request, the SUA layer will send an M-SCTP_RELEASE 
   confirm primitive to Layer Management when the association shutdown 
   is complete.   At the peer SUA Layer, an M-SCTP_RELEASE indication 
   primitive is sent to Layer Management upon abort or successful 
   shutdown of an SCTP association. 
    
   An M-SCTP_STATUS request primitive supports a Layer Management query 
   of the local status of a particular SCTP association.  The SUA layer 
   simply maps the M-SCTP_STATUS request primitive to an SCTP-STATUS 
   primitive to the SCTP layer.  When the SCTP responds, the SUA layer 
   maps the association status information to an M-SCTP_STATUS confirm 
   primitive.  No peer protocol is invoked. 
    
   Similar LM-to-SUA-to-SCTP and/or SCTP-to-SUA-to-LM primitive mappings 
   can be described for the various other SCTP Upper Layer primitives in 
   RFC 2960 [2960] such as INITIALIZE, SET PRIMARY, CHANGE HEARTBEAT, 
   REQUEST HEARTBEAT, GET SRTT REPORT, SET FAILURE THRESHOLD, SET 
   PROTOCOL PARAMETERS, DESTROY SCTP INSTANCE, SEND FAILURE, AND NETWORK 
   STATUS CHANGE.  Alternatively, these SCTP Upper Layer primitives (and 
   Status as well) can be considered for modeling purposes as a Layer 
   Management interaction directly with the SCTP Layer.   
    
   M-NOTIFY indication and M-ERROR indication primitives indicate to 
   Layer Management the notification or error information contained in a 
   received SUA Notify or Error message respectively.  These indications 
   can also be generated based on local SUA events. 
    
   An M-ASP_STATUS request primitive supports a Layer Management query 
   of the status of a particular local or remote ASP.  The SUA layer 
 
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   responds with the status in an M-ASP_STATUS confirm primitive.  No 
   SUA peer protocol is invoked. An M-AS_STATUS request supports a Layer 
   Management query of the status of a particular AS.  The SUA responds 
   with an M-AS_STATUS confirm primitive.  No SUA peer protocol is 
   invoked. 
    
   M-ASP_UP request, M-ASP_DOWN request, M-ASP_ACTIVE request and M-
   ASP_INACTIVE request primitives allow Layer Management at an ASP to 
   initiate state changes.  Upon successful completion, a corresponding 
   confirm primitive is provided by the SUA layer to Layer Management.  
   If an invocation is unsuccessful, an Error indication primitive is 
   provided in the primitive.  These requests result in outgoing ASP Up, 
   ASP Down, ASP Active and ASP Inactive messages to the remote SUA peer 
   at an SGP or IPSP.  
    
4.2.1 Receipt of SUA Peer Management Messages 
    
   Upon successful state changes resulting from reception of ASP Up, ASP 
   Down, ASP Active and ASP Inactive messages from a peer SUA, the SUA 
   layer MAY invoke corresponding M-ASP_UP, M-ASP_DOWN, M-ASP_ACTIVE and 
   M-ASP_INACTIVE, M-AS_ACTIVE, M-AS_INACTIVE, and M-AS_DOWN indication 
   primitives to the local Layer Management. 
    
   M-NOTIFY indication and M-ERROR indication primitives indicate to 
   Layer Management the notification or error information contained in a 
   received SUA Notify or Error message.  These indications can also be 
   generated based on local SUA events. 
    
   All non-Transfer messages, except BEAT and BEAT Ack, SHOULD be sent 
   with sequenced delivery to ensure ordering.  All non-Transfer 
   messages, with the exception of ASPTM, BEAT and BEAT Ack messages 
   SHOULD be sent on SCTP stream '0'.  ASPTM messages MAY be sent on one 
   of the streams used to carry data traffic related to the Routing 
   Context(s), to minimize possible message loss.  BEAT and BEAT Ack 
   messages MAY be sent using out-of-order delivery, and MAY be sent on 
   any stream. 
    
4.3 AS and ASP State Maintenance 
    
   The SUA layer on the SGP maintains the state of each remote ASP, in 
   each Application Server that the ASP is configured to receive 
   traffic, as input to the SUA message distribution function.  
   Similarly, where IPSPs use SUA in a point-to-point fashion, the SUA 
   layer in an IPSP maintains the state of remote IPSPs.  For the 
   purposes of the following procedures, only the SGP/ASP case is 
   described but the SGP side of the procedures also apply to an IPSP 
   sending traffic to an AS consisting of a set of remote IPSPs. 
    
4.3.1 ASP States 
    
   The state of each remote ASP, in each AS that it is configured to 
   operate, is maintained in the SUA layer in the SGP. The state of a 
 
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   particular ASP in a particular AS changes due to events.  The events 
   include: 
    
      * Reception of messages from the peer SUA layer at the ASP; 
      * Reception of some messages from the peer SUA layer at other 
        ASPs in the AS (e.g., ASP Active message indicating 
        "Override"); 
      * Reception of indications from the SCTP layer; or 
      * Local Management intervention. 
    
   The ASP state transition diagram is shown in Figure 4.  The possible 
   states of an ASP are: 
    
   ASP-DOWN:     The remote SUA peer at the ASP is unavailable and/or 
                 the related SCTP association is down.  Initially all 
                 ASPs will be in this state.  An ASP in this state 
                 SHOULD NOT be sent any SUA messages, with the 
                 exception of Heartbeat messages. 
    
   ASP-INACTIVE:  The remote SUA peer at the ASP is available (and the 
                 related SCTP association is up) but application 
                 traffic is stopped.  In this state the ASP MAY be sent 
                 any non-DATA SUA messages. 
    
   ASP-ACTIVE:   The remote SUA peer at the ASP is available and 
                 application traffic is active (for a particular 
                 Routing Context or set of Routing Contexts). 
                                      
              Figure 4: ASP State Transition Diagram (Per AS) 
    
                                      +--------------+  
                                      |              | 
               +----------------------|  ASP-ACTIVE  | 
               |      Other   +-------|              | 
               |   ASP in AS  |       +--------------+ 
               |   Overrides  |           ^     | 
               |              |    ASP    |     | ASP 
               |              |    Active |     | Inactive 
               |              |           |     v 
               |              |       +--------------+ 
               |              |       |              | 
               |              +------>| ASP-INACTIVE | 
               |                      +--------------+ 
               |                          ^     | 
     ASP Down/ |                     ASP  |     | ASP Down / 
     SCTP CDI/ |                     Up   |     | SCTP CDI/ 
     SCTP RI   |                          |     v SCTP RI 
               |                      +--------------+ 
               |                      |              | 
               +--------------------->|   ASP-DOWN   | 
                                      |              | 
                                      +--------------+ 
 
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   SCTP CDI: The SCTP CDI denotes the local SCTP layer's Communication 
   Down Indication to the Upper Layer Protocol (SUA) on an SGP. The 
   local SCTP layer will send this indication when it detects the loss 
   of connectivity to the ASP's peer SCTP layer.  SCTP CDI is understood 
   as either a SHUTDOWN_COMPLETE notification or COMMUNICATION_LOST 
   notification from the SCTP layer. 
    
   SCTP RI: The local SCTP layer's Restart indication to the upper layer 
   protocol (SUA) on an SG.  The local SCTP will send this indication 
   when it detects a restart from the ASP's peer SCTP layer. 
    
4.3.2 AS States 
    
   The state of the AS is maintained in the SUA layer on the SGP.  The 
   state of an AS changes due to events. These events include: 
    
      * ASP state transitions 
      * Recovery timer triggers 
    
   The possible states of an AS are: 
    
   AS-DOWN:    The Application Server is unavailable.  This state 
               implies that all related ASPs are in the ASP-DOWN state 
               for this AS. Initially the AS will be in this state. An 
               Application Server MUST be in the AS-DOWN state before 
               it can be removed from a configuration. 
    
   AS-INACTIVE: The Application Server is available but no application 
               traffic is active (i.e., one or more related ASPs are in 
               the ASP-INACTIVE state, but none in the ASP-ACTIVE 
               state).  The recovery timer T(r) is not running or has 
               expired.  
    
   AS-ACTIVE:  The Application Server is available and application 
               traffic is active.  This state implies that at least one 
               ASP is in the ASP-ACTIVE state. 
    
   AS-PENDING:  An active ASP has transitioned to ASP-INACTIVE or ASP-
               DOWN and it was the last remaining active ASP in the AS.  
               A recovery timer T(r) SHOULD be started and all incoming 
               signalling messages SHOULD be queued by the SGP.  If an 
               ASP becomes ASP-ACTIVE before T(r) expires, the AS is 
               moved to the AS-ACTIVE state and all the queued messages 
               will be sent to the ASP.  
    
   If T(r) expires before an ASP becomes ASP-ACTIVE, and the SGP has no 
   other alternative, the SGP may stop queueing messages and discard all 
   previously queued messages. The AS will move to the AS-INACTIVE state 
   if at least one ASP is in ASP-INACTIVE state, otherwise it will move 
   to AS-DOWN state. 
    
 
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   Figure 5 shows an example AS state machine for the case where the 
   AS/ASP data is pre-configured.  For other cases where the AS/ASP 
   configuration data is created dynamically, there would be differences 
   in the state machine, especially at creation of the AS.   
    
   For example, where the AS/ASP configuration data is not created until 
   Registration of the first ASP, the AS-INACTIVE state is entered 
   directly upon the first successful REG REQ from an ASP.  Another 
   example is where the AS/ASP configuration data is not created until 
   the first ASP successfully enters the ASP-ACTIVE state.  In this case 
   the AS-ACTIVE state is entered directly. 
    

 
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                    Figure 5: AS State Transition Diagram 
    
        +----------+   one ASP trans to ACTIVE   +-------------+ 
        |    AS-   |---------------------------->|     AS-     |       
        | INACTIVE |                             |   ACTIVE    | 
        |          |<---                         |             | 
        +----------+    \                        +-------------+ 
           ^   |         \ Tr Expiry,                ^    | 
           |   |          \ at least one             |    | 
           |   |           \ ASP in ASP-INACTIVE     |    | 
           |   |            \                        |    | 
           |   |             \                       |    | 
           |   |              \                      |    | 
   one ASP |   | all ASP       \            one ASP  |    | Last ACTIVE 
   trans   |   | trans to       \           trans to |    | ASP trans to 
   to      |   | ASP-DOWN        -------\   ASP-     |    | ASP-INACTIVE 
   ASP-    |   |                         \  ACTIVE   |    | or ASP-DOWN 
   INACTIVE|   |                          \          |    | (start Tr) 
           |   |                           \         |    | 
           |   |                            \        |    | 
           |   v                             \       |    v          
        +----------+                          \  +-------------+ 
        |          |                           --|             |       
        | AS-DOWN  |                             | AS-PENDING  | 
        |          |                             |  (queueing) | 
        |          |<----------------------------|             | 
        +----------+    Tr Expiry and no ASP     +-------------+ 
                        in ASP-INACTIVE state 
    
       Tr = Recovery Timer 
    

4.3.2.1 IPSP Considerations 
    
   The AS state diagram for the AS-SG case is applicable for IPSP 
   communication. 
    
4.3.3 SUA Management Procedures for Primitives 
    
   Before the establishment of an SCTP association the ASP state at both 
   the SGP and ASP is assumed to be in the state ASP-DOWN.   
    
   Once the SCTP association is established (see Section 4.2.1) and 
   assuming that the local SUA-User is ready, the local SUA ASP 
   Maintenance (ASPM) function will initiate the relevant procedures, 
   using the ASP Up/ASP Down/ASP Active/ASP Inactive messages to convey 
   the ASP state to the SGP (see Section 4.4.3). 
    
   If the SUA layer subsequently receives an SCTP-COMMUNICATION_DOWN or 
   SCTP-RESTART indication primitive from the underlying SCTP layer, it 
   will inform the Layer Management by invoking the M-SCTP_STATUS 
 
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   indication primitive.  The state of the ASP will be moved to ASP-
   DOWN. 
    
   In the case of SCTP-COMMUNICATION_DOWN, the SCTP client MAY try to 
   re-establish the SCTP association.  This MAY be done by the SUA layer 
   automatically, or Layer Management MAY re-establish using the M-
   SCTP_ESTABLISH request primitive.  
    
   In the case of an SCTP-RESTART indication at an ASP, the ASP is now 
   considered by its SUA peer to be in the ASP-DOWN state.  The ASP, if 
   it is to recover, must begin any recovery with the ASP-Up procedure. 
    
4.3.4 ASPM Procedures for Peer-to-Peer Messages 

4.3.4.1 ASP Up Procedures 
    
   After an ASP has successfully established an SCTP association to an 
   SGP, the SGP waits for the ASP to send an ASP Up message, indicating 
   that the ASP SUA peer is available.  The ASP is always the initiator 
   of the ASP Up message.  This action MAY be initiated at the ASP by an 
   M-ASP_UP request primitive from Layer Management or MAY be initiated 
   automatically by an SUA management function. 
    
   When an ASP Up message is received at an SGP and internally the 
   remote ASP is in the ASP-DOWN state and not considered locked-out for 
   local management reasons, the SGP marks the remote ASP in the state 
   ASP-INACTIVE and informs Layer Management with an M-ASP_Up indication 
   primitive.  If the SGP is aware, via current configuration data, 
   which Application Servers the ASP is configured to operate in, the 
   SGP updates the ASP state to ASP-INACTIVE in each AS that it is a 
   member.   
    
   Alternatively, the SGP may move the ASP into a pool of Inactive ASPs 
   available for future configuration within Application Server(s), 
   determined in a subsequent Registration Request or ASP Active 
   procedure.  If the ASP Up message contains an ASP Identifier, the SGP 
   should save the ASP Identifier for that ASP.  The SGP MUST send an 
   ASP Up Ack message in response to a received ASP Up message even if 
   the ASP is already marked as ASP-INACTIVE at the SGP.   
    
   If for any local reason (e.g., management lock-out) the SGP cannot 
   respond with an ASP Up Ack message, the SGP responds to an ASP Up 
   message with an Error message with Reason "Refused - Management 
   Blocking".   
    
   At the ASP, the ASP Up Ack message received is not acknowledged. 
   Layer Management is informed with an M-ASP_UP confirm primitive.   
    
   When the ASP sends an ASP Up message it starts timer T(ack).  If the 
   ASP does not receive a response to an ASP Up message within T(ack), 
   the ASP MAY restart T(ack) and resend ASP Up messages until it 
 
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   receives an ASP Up Ack message.  T(ack) is provisionable, with a 
   default of 2 seconds.  Alternatively, retransmission of ASP Up 
   messages MAY be put under control of Layer Management.  In this 
   method, expiry of T(ack) results in an M-ASP_UP confirm primitive  
   carrying a negative indication.   
    
   The ASP must wait for the ASP Up Ack message before sending any other 
   SUA messages (e.g., ASP Active or REG REQ).  If the SGP receives any 
   other SUA messages before ASPUP message is received (other than ASPDN 
   - see section 4.3.4.2), the SGP SHOULD discard them. 
    
   If an ASP Up message is received and internally the remote ASP is in 
   the ASP-ACTIVE state, an ASP Up Ack message is returned, as well as 
   an Error message ("Unexpected Message), and the remote ASP state is 
   changed to ASP-INACTIVE in all relevant Application Servers. 
    
   If an ASP Up message is received and internally the remote ASP is 
   already in the ASP-INACTIVE state, an ASP Up Ack message is returned 
   and no further action is taken. 

4.3.4.1.1 SUA Version Control 
    
   If an ASP Up message with an unsupported version is received, the 
   receiving end responds with an Error message, indicating the version 
   the receiving node supports and notifies Layer Management. 
    
   This is useful when protocol version upgrades are being performed in 
   a network.  A node upgraded to a newer version should support the 
   older versions used on other nodes it is communicating with.  Because 
   ASPs initiate the ASP Up procedure it is assumed that the Error 
   message would normally come from the SGP. 

4.3.4.1.2 IPSP Considerations 
    
   An IPSP may be considered in the ASP-INACTIVE state after and ASPUP 
   or ASPUP Ack has been received from it.  An IPSP can be considered 
   in the ASP-DOWN state after an ASPDN or ASPDN Ack has been received 
   from it. The IPSP may inform Layer Management of the change in state 
   of the remote IPSP using M-ASP_UP or M-ASP_DN indication or 
   confirmation primitives. 
    
   Alternatively, an interchange of ASPUP messages from each end can be 
   performed. This option follows the ASP state transition diagram. It 
   would need four messages for completion. 
    
   If for any local reason (e.g., management lock-out) and IPSP cannot 
   respond to an ASP Up message with an ASP Up Ack message, it responds 
   to an ASP Up message with an Error message with Reason "Refused - 
   Management Blocking" and leaves the remote IPSP in the ASP-DOWN 
   state. 
    
 
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4.3.4.2 ASP Down Procedures 
    
   The ASP will send an ASP Down message to an SGP when the ASP wishes 
   to be removed from service in all Application Servers that it is a 
   member and no longer receive any DATA, SSNM or ASPTM messages.  This 
   action MAY be initiated at the ASP by an M-ASP_DOWN request primitive 
   from Layer Management or MAY be initiated automatically by an SUA 
   management function.    
    
   Whether the ASP is permanently removed from any AS is a function of 
   configuration management.  In the case where the ASP previously used 
   the Registration procedures (see Section 4.3.5) to register within 
   Application Servers but has not deregistered from all of them prior 
   to sending the ASP Down message, the SGP MUST consider the ASP as 
   Deregistered in all Application Servers that it is still a member. 
    
   The SGP marks the ASP as ASP-DOWN, informs Layer Management with an 
   M-ASP_Down indication primitive, and returns an ASP Down Ack message 
   to the ASP.  
    
   The SGP MUST send an ASP Down Ack message in response to a received 
   ASP Down message from the ASP even if the ASP is already marked as 
   ASP-DOWN at the SGP.   
    
   At the ASP, the ASP Down Ack message received is not acknowledged. 
   Layer Management is informed with an M-ASP_DOWN confirm primitive.  
   If the ASP receives an ASP Down Ack without having sent an ASP Down 
   message, the ASP should now consider itself as in the ASP-DOWN state.  
   If the ASP was previously in the ASP-ACTIVE or ASP_INACTIVE state, 
   the ASP should then initiate procedures to return itself to its 
   previous state. 
    
   When the ASP sends an ASP Down message it starts timer T(ack).  If 
   the ASP does not receive a response to an ASP Down message within 
   T(ack), the ASP MAY restart T(ack) and resend ASP Down messages until 
   it receives an ASP Down Ack message.  T(ack) is provisionable, with a 
   default of 2 seconds.  Alternatively, retransmission of ASP Down 
   messages MAY be put under control of Layer Management.  In this 
   method, expiry of T(ack) results in an M-ASP_DOWN confirm primitive 
   carrying a negative indication.  

4.3.4.3 ASP Active Procedures 
    
   Anytime after the ASP has received an ASP Up Ack message from the SGP 
   or IPSP, the ASP MAY send an ASP Active message to the SGP indicating 
   that the ASP is ready to start processing traffic.  This action MAY 
   be initiated at the ASP by an M-ASP_ACTIVE request primitive from 
   Layer Management or MAY be initiated automatically by an SUA 
   management function.  In the case where an ASP wishes to process the 
   traffic for more than one Application Server across a common SCTP 
   association, the ASP Active message(s) SHOULD contain a list of one 
 
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   or more Routing Contexts to indicate for which Application Servers 
   the ASP Active message applies. It is not necessary for the ASP to 
   include all Routing Contexts of interest in a single ASP Active 
   message, thus requesting to become active in all Routing Contexts at 
   the same time.  Multiple ASP Active messages MAY be used to activate 
   within the Application Servers independently, or in sets.  In the 
   case where an ASP Active message does not contain a Routing Context 
   parameter, the receiver must know, via configuration data, which 
   Application Server(s) the ASP is a member. 
    
   For the Application Servers that the ASP can successfully activate, 
   the SGP or IPSP responds with one or more ASP Active Ack messages, 
   including the associated Routing Context(s) and reflecting any 
   Traffic Mode Type values present in the related ASP Active message.  
   The Routing Context parameter MUST be included in the ASP Active Ack 
   message(s) if the received ASP Active message contained any Routing 
   Contexts.  Depending on any Traffic Mode Type request in the ASP 
   Active message or local configuration data if there is no request, 
   the SGP moves the ASP to the correct ASP traffic state within the 
   associated Application Server(s). Layer Management is informed with 
   an M-ASP_Active indication. If the SGP or IPSP receives any Data 
   messages before an ASP Active message is received, the SGP or IPSP 
   MAY discard them.  By sending an ASP Active Ack message, the SGP or 
   IPSP is now ready to receive and send traffic for the related Routing 
   Context(s).  The ASP SHOULD NOT send Data messages for the related 
   Routing Context(s) before receiving an ASP Active Ack message, or it 
   will risk message loss. 
    
   Multiple ASP Active Ack messages MAY be used in response to an ASP 
   Active message containing multiple Routing Contexts, allowing the SGP 
   or IPSP to independently acknowledge the ASP Active message for 
   different (sets of) Routing Contexts.  The SGP or IPSP MUST send an
   Error message ("Invalid Routing Context") for each Routing Context 
   value that cannot be successfully activated.  
    
   In the case where an "out-of-the-blue" ASP Active message is received 
   (i.e., the ASP has not registered with the SG or the SG has no static 
   configuration data for the ASP), the message MAY be silently 
   discarded.  
    
   The SGP MUST send an ASP Active Ack message in response to a received 
   ASP Active message from the ASP, if the ASP is already marked in the 
   ASP-ACTIVE state at the SGP.   
    
   At the ASP, the ASP Active Ack message received is not acknowledged. 
   Layer Management is informed with an M-ASP_ACTIVE confirm primitive.  
   It is possible for the ASP to receive Data message(s) before the ASP 
   Active Ack message as the ASP Active Ack and Data messages from an SG 
   or IPSP may be sent on different SCTP streams.  Message loss is 
   possible, as the ASP does not consider itself in the ASP-ACTIVE state 
   until reception of the ASP Active Ack message. 
    
 
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   When the ASP sends an ASP Active message it starts timer T(ack).  If 
   the ASP does not receive a response to an ASP Active message within 
   T(ack), the ASP MAY restart T(ack) and resend ASP Active messages 
   until it receives an ASP Active Ack message.  T(ack) is 
   provisionable, with a default of 2 seconds.  Alternatively, 
   retransmission of ASP Active messages MAY be put under control of 
   Layer Management.  In this method, expiry of T(ack) results in an M-
   ASP_ACTIVE confirm primitive carrying a negative indication.   
    
   There are three modes of Application Server traffic handling in the 
   SGP SUA layer:  Override, Load-share and Broadcast.  When included, 
   the Traffic Mode Type parameter in the ASP Active message indicates 
   the traffic-handling mode to be used in a particular Application 
   Server. If the SGP determines that the mode indicated in an ASP 
   Active message is unsupported or incompatible with the mode currently 
   configured for the AS, the SGP responds with an Error message 
   ("Unsupported / Invalid Traffic Handling Mode").  If the traffic-
   handling mode of the Application Server is not already known via 
   configuration data, then the traffic-handling mode indicated in the 
   first ASP Active message causing the transition of the Application 
   Server state to AS-ACTIVE MAY be used to set the mode. 
    
   In the case of an Override mode AS, reception of an ASP Active 
   message at an SGP causes the (re)direction of all traffic for the AS 
   to the ASP that sent the ASP Active message.  Any previously active 
   ASP in the AS is now considered to be in state ASP-INACTIVE and 
   SHOULD no longer receive traffic from the SGP within the AS.  The SGP 
   or IPSP then MUST send a Notify message ("Alternate ASP Active") to 
   the previously active ASP in the AS, and SHOULD stop traffic to/from 
   that ASP.  The ASP receiving this Notify MUST consider itself now in 
   the ASP-INACTIVE state, if it is not already aware of this via inter-
   ASP communication with the Overriding ASP. 
    
   In the case of a Loadshare mode AS, reception of an ASP Active 
   message at an SGP or IPSP causes the direction of traffic to the ASP 
   sending the ASP Active message, in addition to all the other ASPs 
   that are currently active in the AS.  The algorithm at the SGP for 
   load-sharing traffic within an AS to all the active ASPs is 
   implementation dependent.  The algorithm could, for example, be round 
   robin or based on information in the Data message (e.g., the SLS or 
   SSN).   
    
   An SGP or IPSP, upon reception of an ASP Active message for the first 
   ASP in a Loadshare AS, MAY choose not to direct traffic to a newly 
   active ASP until it determines that there are sufficient resources to 
   handle the expected load (e.g., until there are "n" ASPs in state 
   ASP-ACTIVE in the AS). 
    
   All ASPs within a load-sharing mode AS must be able to process any 
   Data message received for the AS, to accommodate any potential fail-
   over or rebalancing of the offered load. 
    
 
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   In the case of a Broadcast mode AS, reception of an ASP Active 
   message at an SGP or IPSP causes the direction of traffic to the ASP 
   sending the ASP Active message, in addition to all the other ASPs 
   that are currently active in the AS. The algorithm at the SGP for 
   broadcasting traffic within an AS to all the active ASPs is a simple 
   broadcast algorithm, where every message is sent to each of the 
   active ASPs.  An SGP or IPSP, upon reception of an ASP Active message 
   for the first ASP in a Broadcast AS, MAY choose not to direct traffic 
   to a newly active ASP until it determines that there are sufficient 
   resources to handle the expected load (e.g., until there are "n" ASPs 
   in state ASP-ACTIVE in the AS).  
    
   Whenever an ASP in a Broadcast mode AS becomes ASP-ACTIVE, the SGP 
   MUST tag the first DATA message broadcast in each SCTP stream with a 
   unique Correlation Id parameter.  The purpose of this Correlation Id 
   is to permit the newly active ASP to synchronize it's processing of 
   traffic in each ordered stream with the other ASPs in the broadcast 
   group. 

4.3.4.3.1 IPSP Consideratoins 
    
   Either of the IPSPs can initiate communication. When an IPSP receives 
   an ASP Active, it should mark the peer as ASP-ACTIVE and return an 
   ASP Active Ack message. An ASP receiving an ASP Active Ack message 
   may mark the peer as ASP-Active, if it is not already in the ASP-
   ACTIVE state.  
    
   Alternatively, an interchange of ASPAC messages from each end can be 
   performed. This option follows the ASP state transition diagram and 
   gives the additional advantage of selecting a particular AS to be 
   activated from each end. It is especially useful when an IPSP is 
   serving more than one AS. It would need four messages for completion. 

4.3.4.4 ASP Inactive Procedures 
    
   When an ASP wishes to withdraw from receiving traffic within an AS, 
   the ASP sends an ASP Inactive message to the SGP or IPSP.  This 
   action MAY be initiated at the ASP by an M-ASP_INACTIVE request 
   primitive from Layer Management or MAY be initiated automatically by 
   an SUA management function.  In the case where an ASP is processing 
   the traffic for more than one Application Server across a common SCTP 
   association, the ASP Inactive message contains one or more Routing 
   Contexts to indicate for which Application Servers the ASP Inactive 
   message applies.  In the case where an ASP Inactive message does not 
   contain a Routing Context parameter, the receiver must know, via 
   configuration data, which Application Servers the ASP is a member and 
   move the ASP to the ASP-INACTIVE state in each all Application 
   Servers.  In the case of an Override mode AS, where another ASP has 
   already taken over the traffic within the AS with an ASP Active 
   ("Override") message, the ASP that sends the ASP Inactive message is 
   already considered by the SGP to be in state ASP-INACTIVE.  An ASP 
 
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   Inactive Ack message is sent to the ASP, after ensuring that all 
   traffic is stopped to the ASP.  
    
   In the case of a Load-share mode AS, the SGP moves the ASP to the 
   ASP-INACTIVE state and the AS traffic is re-allocated across the 
   remaining ASPs in the state ASP-ACTIVE, as per the load-sharing 
   algorithm currently used within the AS.  A Notify message 
   ("Insufficient ASP resources active in AS") MAY be sent to all 
   inactive ASPs, if required.  An ASP Inactive Ack message is sent to 
   the ASP after all traffic is halted and Layer Management is informed 
   with an M-ASP_INACTIVE indication primitive.  
    
   In the case of a Broadcast mode AS, the SGP moves the ASP to the ASP-
   INACTIVE state and the AS traffic is broadcast only to the remaining 
   ASPs in the state ASP-ACTIVE. A Notify message ("Insufficient ASP 
   resources active in AS") MAY be sent to all inactive ASPs, if 
   required. An ASP Inactive Ack message is sent to the ASP after all 
   traffic is halted and Layer Management is informed with an M-
   ASP_INACTIVE indication primitive. 
    
   Multiple ASP Inactive Ack messages MAY be used in response to an ASP 
   Inactive message containing multiple Routing Contexts, allowing the 
   SGP or IPSP to independently acknowledge for different (sets of) 
   Routing Contexts.  The SGP or IPSP sends an Error message ("Invalid 
   Routing Context") message for each invalid or unconfigured Routing 
   Context value in a received ASP Inactive message. 
    
   The SGP MUST send an ASP Inactive Ack message in response to a 
   received ASP Inactive message from the ASP and the ASP is already 
   marked as ASP-INACTIVE at the SGP.   
    
   At the ASP, the ASP Inactive Ack message received is not 
   acknowledged.  Layer Management is informed with an M-ASP_INACTIVE 
   confirm primitive.  If the ASP receives an ASP Inactive Ack without 
   having sent an ASP Inactive message, the ASP should now consider 
   itself as in the ASP-INACTIVE state.  If the ASP was previously in 
   the ASP-ACTIVE state, the ASP should then initiate procedures to 
   return itself to its previous state. When the ASP sends an ASP 
   Inactive message it starts timer T(ack).  If the ASP does not receive 
   a response to an ASP Inactive message within T(ack), the ASP MAY 
   restart T(ack) and resend ASP Inactive messages  until it receives an 
   ASP Inactive Ack message.  T(ack) is provisionable, with a default of 
   2 seconds.  Alternatively, retransmission of ASP Inactive messages 
   MAY be put under control of Layer Management.  In this method, expiry 
   of T(ack) results in a M-ASP_Inactive confirm primitive carrying a 
   negative indication.   
    
   If no other ASPs in the Application Server are in the state ASP-
   ACTIVE, the SGP MUST send a Notify message ("AS-Pending") to all of 
   the ASPs in the AS which are in the state ASP-INACTIVE.  The SGP 
   SHOULD start buffering the incoming messages for T(r) seconds, after 
   which messages MAY be discarded.  T(r) is configurable by the network 
 
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   operator.  If the SGP receives an ASP Active message from an ASP in 
   the AS before expiry of T(r), the buffered traffic is directed to 
   that ASP and the timer is cancelled.  If T(r) expires, the AS is 
   moved to the AS-INACTIVE state. 

4.3.4.4.1 IPSP Considerations  
        
   An IPSP may be considered in the ASP-INACTIVE state by a remote IPSP 
   after an ASP Inactive or ASP Inactive Ack message has been received 
   from it.  
    
   Alternatively, an interchange of ASPIA messages from each end can be 
   performed. This option follows the ASP state transition diagram and 
   gives the additional advantage of selecting a particular AS to be 
   deactivated from each end. It is especially useful when an IPSP is 
   serving more than one AS. It would need four messages for completion.  

4.3.4.5 Notify Procedures 
    
   A Notify message reflecting a change in the AS state MUST be sent to 
   all ASPs in the AS, except those in the ASP-DOWN state, 
   withappropriate Status Information and any ASP Identifier of the 
   failed ASP.  At the ASP, Layer Management is informed with an M-
   NOTIFY indication primitive.  The Notify message must be sent whether 
   the AS state change was a result of an ASP failure or reception of an 
   ASP State management (ASPSM) / ASP Traffic Management (ASPTM) 
   message.  In the second case, the Notify message MUST be sent after 
   any ASP State or Traffic Management related acknowledgement messages  
   (e.g., ASP Up Ack, ASP Down Ack, ASP Active Ack, or ASP Inactive 
   Ack).   
    
   In the case where a Notify ("AS-PENDING") message is sent by an SGP 
   that now has no ASPs active to service the traffic, or where a Notify 
   ("Insufficient ASP resources active in AS") message MUST be sent in 
   the Loadshare or Broadcast mode, the Notify message does not 
   explicitly compel the ASP(s) receiving the message to become active.  
   The ASPs remain in control of what (and when) traffic action is 
   taken. 
    
   In the case where a Notify message does not contain a Routing Context 
   parameter, the receiver must know, via configuration data, of which 
   Application Servers the ASP is a member and take the appropriate 
   action in each AS. 

4.3.4.5.1 IPSP Considerations (NTFY) 
    
   Notify works in the same manner as in the SG-AS case. One of the 
   IPSPs can send this message to any remote IPSP that is not in the 
   ASP-DOWN state. 

 
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4.3.4.6 Heartbeat Procedures 
    
   The optional Heartbeat procedures MAY be used when operating over 
   transport layers that do not have their own heartbeat mechanism for 
   detecting loss of the transport association (i.e., other than SCTP).   
    
   Either SUA peer may optionally send Heartbeat messages periodically, 
   subject to a provisionable timer T(beat).  Upon receiving a Heartbeat 
   message, the SUA peer MUST respond with a Heartbeat Ack message.  
    
   If no Heartbeat Ack message (or any other SUA message) is received 
   from the SUA peer within 2*T(beat), the remote SUA peer is considered 
   unavailable.  Transmission of Heartbeat messages is stopped and the 
   signalling process SHOULD attempt to re-establish communication if it 
   is configured as the client for the disconnected SUA peer. 
    
   The Heartbeat message may optionally contain an opaque Heartbeat Data 
   parameter that MUST be echoed back unchanged in the related Heartbeat 
   Ack message.  The sender, upon examining the contents of the returned 
   Heartbeat Ack message, MAY choose to consider the remote SUA peer as 
   unavailable.  The contents/format of the Heartbeat Data parameter is 
   implementation-dependent and only of local interest to the original 
   sender.  The contents may be used, for example, to support a 
   Heartbeat sequence algorithm (to detect missing Heartbeats), and/or a 
   timestamp mechanism (to evaluate delays). 
    
   Note: Heartbeat related events are not shown in Figure 4 "ASP state 
   transition diagram".   
    
4.4 Routing Key Management Procedures 
    
4.4.1 Registration 
    
   An ASP MAY dynamically register with an SGP as an ASP within an 
   Application Server using the REG REQ message. A Routing Key parameter 
   in the REG REQ message specifies the parameters associated with the 
   Routing Key.   
    
   The SGP examines the contents of the received Routing Key parameter 
   and compares it with the currently provisioned Routing Keys.  If the 
   received Routing Key matches an existing SGP Routing Key entry, and 
   the ASP is not currently included in the list of ASPs for the related 
   Application Server, the SGP MAY authorize the ASP to be added to the 
   AS.  Or, if the Routing Key does not currently exist and the received 
   Routing Key data is valid and unique, an SGP supporting dynamic 
   configuration MAY authorize the creation of a new Routing Key and 
   related Application Server and add the ASP to the new AS.  In either 
   case, the SGP returns a Registration Response message to the ASP, 
   containing the same Local-RK-Identifier as provided in the initial 
   request, and a Registration Result "Successfully Registered".  A 
   unique Routing Context value assigned to the SGP Routing Key is 
 
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   included. The method of Routing Context value assignment at the SGP 
   is implementation dependent but must be guaranteed to be unique for 
   each Application Server or Routing Key supported by the SGP.   If the 
   SGP determines that the received Routing Key data is invalid, or 
   contains invalid parameter values, the SGP returns a Registration 
   Response message to the ASP, containing a Registration Result "Error 
   - Invalid Routing Key", "Error - Invalid DPC", "Error - Invalid 
   Network Appearance" as appropriate. 
    
   If the SGP does not support the registration procedure, the SGP 
   returns an Error message to the ASP, with an error code of 
   "Unsupported Message Type". 
    
   If the SGP determines that a unique Routing Key cannot be created, 
   the SGP returns a Registration Response message to the ASP, with a 
   Registration Status of "Error - "Cannot Support Unique Routing." An 
   incoming signalling message received at an SGP should not match 
   against more than one Routing Key. 
    
   If the SGP does not authorize the registration request, the SGP 
   returns a REG RSP message to the ASP containing the Registration 
   Result "Error - Permission Denied". 
    
   If an SGP determines that a received Routing Key does not currently 
   exist and the SGP does not support dynamic configuration, the SGP 
   returns a Registration Response message to the ASP, containing a 
   Registration Result "Error - Routing Key not Currently Provisioned". 
    
   If an SGP determines that a received Routing Key does not currently 
   exist and the SGP supports dynamic configuration but does not have 
   the capacity to add new Routing Key and Application Server entries, 
   the SGP returns a Registration Response message to the ASP, 
   containing a Registration Result "Error - Insufficient Resources". 
    
   If an SGP determines that one or more of the Routing Key parameters 
   are not supported for the purpose of creating new Routing Key 
   entries, the SGP returns a Registration Response message to the ASP, 
   containing a Registration Result "Error - Unsupported RK parameter 
   field".  This result MAY be used if, for example, the SGP does not 
   support RK Address parameter. 
    
   A Registration Response "Error - Unsupported Traffic Handling Mode" 
   is returned if the Routing Key in the REG REQ contains a Traffic 
   Handling Mode that is inconsistent with the presently configured mode 
   for the matching Application Server. 
    
   An ASP MAY register multiple Routing Keys at once by including a 
   number of Routing Key parameters in a single REG REQ message.  The 
   SGP MAY respond to each registration request in a single REG RSP 
   message, indicating the success or failure result for each Routing 
   Key in a separate Registration Result parameter.  Alternatively the 
   SGP MAY respond with multiple REG RSP messages, each with one or more 
 
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   Registration Result parameters.  The ASP uses the Local-RK-Identifier 
   parameter to correlate the requests with the responses. 
    
   An ASP MAY modify an existing Routing Key by including a Routing 
   Context parameter in the REG REQ.  If the SGP determines that the 
   Routing Context applies to an existing Routing Key, the SG MAY adjust 
   the existing Routing Key to match the new information provided in the 
   Routing Key parameter.  A Registration Response "Routing Context 
   Registionation Refused" is returned if the SGP does not accept the 
   modification of the Routing Key. 
    
   Upon successful registration of an ASP in an AS, the SGP can now send 
   related SS7 Signalling Network Management messaging, if this did not 
   previously start upon the ASP transitioning to state ASP-INACTIVE 
    
4.4.2 Deregistration 
    
   An ASP MAY dynamically deregister with an SGP as an ASP within an 
   Application Server using the DEREG REQ message.  A Routing Context 
   parameter in the DEREG REQ message specifies which Routing Keys to 
   de-register.  An ASP SHOULD move to the ASP-INACTIVE state for an 
   Application Server before attempting to deregister the Routing Key 
   (i.e., deregister after receiving an ASP Inactive Ack).  Also, an ASP 
   SHOULD deregister from all Application Servers that it is a member 
   before attempting to move to the ASP-Down state.   
    
   The SGP examines the contents of the received Routing Context 
   parameter and validates that the ASP is currently registered in the 
   Application Server(s) related to the included Routing Context(s).  If 
   validated, the ASP is de-registered as an ASP in the related 
   Application Server.   
    
   The deregistration procedure does not necessarily imply the deletion 
   ofRouting Key and Application Server configuration data at the SGP. 
   Other ASPs may continue to be associated with the Application Server, 
   in which case the Routing Key data MUST NOT be deleted.  If a 
   Deregistration results in no more ASPs in an Application Server, an 
   SGP MAY delete the Routing Key data. 
    
   The SGP acknowledges the deregistration request by returning a DEREG 
   RSP message to the requesting ASP.  The result of the deregistration 
   is found in the Deregistration Result parameter, indicating success 
   or failure with cause. 
    
   An ASP MAY deregister multiple Routing Contexts at once by including 
   a number of Routing Contexts in a single DEREG REQ message.  The SGP 
   MAY respond to each deregistration request in a single DEREG RSP 
   message, indicating the success or failure result for each Routing 
   Context in a separate Deregistration Result parameter.   
    
4.4.3 IPSP Considerations (REG/DEREG) 
    
 
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   The Registration/Deregistration procedures work in the IPSP cases in 
   the same way as in AS-SG cases.  An IPSP may register an RK in the 
   remote IPSP.  An IPSP is responsible for deregistering the RKs that 
   it has registered. 
    
4.5 Availability and/or Congestion Status of SS7 Destination Support 
    
4.5.1 At an SGP 
    
   On receiving an MTP-PAUSE, MTP-RESUME or MTP-STATUS indication 
   primitive from the nodal inter-working function at an SGP, the SGP 
   SUA layer will send a corresponding SS7 Signalling Network Management 
   (SSNM) DUNA, DAVA, SCON, or DUPU message (see Section 3.4) to the SUA 
   peers at concerned ASPs.  The SUA layer must fill in various fields 
   of the SSNM messages consistently with the information received in 
   the primitives.   
    
   The SGP SUA layer determines the set of concerned ASPs to be informed 
   based on the specific SS7 network for which the primitive indication 
   is relevant. In this way, all ASPs configured to send/receive traffic 
   within a particular network appearance are informed.  If the SGP 
   operates within a single SS7 network appearance, then all ASPs are 
   informed.  
    
   DUNA, DAVA, SCON, and DRST messages MUST be sent sequentially and 
   processed at the receiver in the order sent.  SCTP stream "0" is used 
   to provide the sequencing. The only exception to this is if the 
   international congestion method (see Q.704) is used.  If so, the 
   Unordered bit in the SCTP DATA chunk MAY be used for the SCON 
   message. 
    
   Sequencing is not required for the DUPU or DAUD messages, which MAY 
   be sent un-sequenced.  Again, SCTP stream 0 is used, with optional 
   use of the Unordered bit in the SCTP DATA chunk. 
    
4.5.2 At an ASP 

4.5.2.1 Single SGP Configurations 
    
   At an ASP, upon receiving an SS7 Signalling Network Management (SSNM) 
   message from the remote SUA Peer, the SUA layer invokes the 
   appropriate primitive indications to the resident SUA-Users.  Local 
   management is informed. 
    
   In the case where a local event has caused the unavailability or 
   congestion status of SS7 destinations, the SUA layer at the ASP 
   SHOULD pass up appropriate indications in the primitives to the SUA 
   User, as though equivalent SSNM messages were received.  For example, 
   the loss of an SCTP association to an SGP may cause the 
   unavailability of a set of SS7 destinations.  MTP-PAUSE indication 
   primitives to the SUA User are appropriate.   
 
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   Implementation Note: To accomplish this, the SUA layer at an ASP 
   maintains the status of routes via the SG(P). 

4.5.2.2 Multiple SGP Configurations 
    
   At an ASP, upon receiving a Signalling Network Management message 
   from the remote SUA Peer, the SUA layer updates the status of the 
   affected route(s) via the originating SGP and determines, whether or 
   not the overall availability or congestion status of the effected 
   destination(s) has changed. If so, the SUA layer invokes the 
   appropriate primitive indications to the resident SUA-Users.  Local 
   management is informed.   
    
4.5.3 ASP Auditing 
    
   An ASP may optionally initiate an audit procedure to enquire of an 
   SGP the availability and, if the national congestion method with 
   multiple congestion levels and message priorities is used, congestion 
   status of an SS7 destination or set of destinations.  A Destination 
   Audit (DAUD) message is sent from the ASP to the SGP requesting the 
   current availability and congestion status of one or more SS7 
   Destination Point Codes. 
    
   The DAUD message MAY be sent un-sequenced. The ASP MAY send the DAUD 
   in the following cases:   
    
      - Periodic.  A Timer originally set upon reception of a DUNA, 
                   SCON or DRST message has expired without a 
                   subsequent DAVA, DUNA, SCON or DRST message updating 
                   the availability/congestion status of the affected 
                   Destination Point Codes.  The Timer is reset upon 
                   issuing a DAUD.  In this case the DAUD is sent to 
                   the SGP that originally sent the SSNM message.     
    
      - Isolation.  The ASP is newly ASP-INACTIVE or ASP-ACTIVE or has 
                   been isolated from an SGP for an extended period.  
                   The ASP MAY request the availability/congestion 
                   status of one or more SS7 destinations to which it 
                   expects to communicate. 
    
   In the first of the cases above, the auditing procedure must not be 
   invoked for the case of a received SCON message containing a 
   congestion level value of "no congestion" or undefined" (i.e., 
   congestion Level = "0").  This is because the value indicates either 
   congestion abatement or that the ITU MTP3 international congestion 
   method is being used.  In the international congestion method, the 
   MTP3 layer at the SGP does not maintain the congestion status of any 
   destinations and therefore the SGP cannot provide any congestion
   information in response to the DAUD.  For the same reason, in the 

 
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   second of the cases above a DAUD message cannot reveal any congested 
   destination(s). 
    
   The SGP MUST respond to a DAUD message with the MTP3 availability / 
   congested status of the routeset associated with each Destination 
   Point Code(s) in the DAUD message.  The status of each SS7 
   destination requested is indicated in a DUNA message (if 
   unavailable), a DAVA message (if available), or a DRST (if restricted 
   and the SGP supports this feature).  If the SS7 destination is 
   available and congested, the SGP responds with an SCON message in 
   addition to the DAVA message.  If the SS7 destination is restricted 
   and congested, the SGP responds with an SCON message in addition to 
   the DRST.  If the SGP has no information on the availability / 
   congestion status of the SS7 destination, the SGP responds with a 
   DUNA message, as it has no routing information to allow it to route 
   traffic to this destination 
    
   Any DUNA or DAVA message in response to a DAUD message MAY contain a 
   list of up to sixteen Affected Point Codes.  
    
4.6 MTP3 Restart 
    
   In the case where the MTP3 in the SG undergoes an MTP restart, event 
   communication SHOULD be handled as follows: 
    
   When the SG discovers SS7 network isolation, the SGPs send an 
   indication to all concerned available ASPs (i.e., ASPs in the ASP-
   ACTIVE state) using DUNA messages for the concerned destinations.  
   When the SG has completed the MTP Restart procedure, the SUA layer 
   at the SGPs inform all concerned ASPs in the ASP-ACTIVE state of any 
   available/restricted SS7 destinations using the DAVA/DRST message.  
   No message is necessary for those destinations still unavailable 
   after the restart procedure.   
    
   When the SUA layer at an ASP receives a DUNA message indicating SS7 
   destination unavailability at an SG, Users will stop any affected 
   traffic to this destination. When the SUA layer receives a DAVA/DRST 
   message, Users can resume traffic to the newly available SS7 
   destination via this SGP, provided the ASP is in the ASP-ACTIVE 
   state towards this SGP. 
    
   The ASP MAY choose to audit the availability of unavailable 
   destinations by sending DAUD messages. This would be for example the 
   case when an AS becomes active at an ASP and does not have up to 
   date destination statuses.  If MTP restart is then in progress at 
   the SG, the SGP returns a DUNA message for that destination, even if 
   it received an indication that the destination became available or 
   restricted.  
    

 
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4.7 SCCP - SUA Interworking at the SG 
 
4.7.1 Segmenting / Reassembly 
    
   When it is expected that signalling messages will not fit into a PDU 
   of the most restrictive transport technology used (e.g. 272-SIF of 
   MTP3), then segmenting/reassembly could be performed at the SG, ASP 
   or IPSP. If the SG, ASP or IPSP is incapable of performing a 
   necessary segmentation/reassembly, it can inform the peer of the 
   failure using the appropriate error in a CLDR or RESRE/COERR message. 
    
4.7.2 Support for Loadsharing 
    
   Within an AS (identified by RK/RC parameters) several loadsharing 
   ASPs may be active.  
    
   However, in order to assure the correct processing of TCAP 
   transactions or SCCP connections, the loadsharing scheme used at the 
   SG must make sure that messages continuing or ending the 
   ransactions/connections arrive at the same ASP where the initial 
   message (TC_Query, TC_Begin, CR) was sent to/received from. 
    
   When the ASP can be identified uniquely based on RK parameters (e.g. 
   unique DPC or GT), loadsharing is not required. When the ASPs in the 
   AS share state or use an internal distribution mechanism, the SG must 
   only take into account the in-sequence-delivery requirement.  In case 
   of SCCP CO traffic, when the coupled approach is used, loadsharing of 
   messages other than CR is not required. 
    
   If these assumptions cannot be made, both SG and ASP should support 
   the following general procedure in a loadsharing environment. 

4.7.2.1 Association Setup, ASP going active 
    
   After association setup and registration, an ASP normally goes active 
   for each AS it registered for. In the ASPAC message, the ASP includes 
   a TID and/or DRN Label Parameter, if applicable for the AS in 
   question. All the ASPs within the AS must specify a unique label at a 
   fixed position in the TID or DRN parameter. The same ASPAC message is 
   sent to each SG used for interworking with the SS7 network. 
    
   The SG builds, per RK, a list of ASPs that have registered for it. 
   The SG can now build up and update a distribution table for a certain 
   Routing Context, any time the association is (re-)established and the 
   ASP goes active. The SG has to perform some trivial plausibility 
   checks on the parameters: 
    
   - Start and End parameters values are between 0 and 31 for TID. 
   - Start and End parameters values are between 0 and 23 for DRN  
   - 0 < (Start - End + 1) <= 16 (label length maximum 16-bit) 
   - Start values are the same for each ASP within a RC 
 
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   - End values are the same for each ASP within a RC  
   - TID and DRN Label values must be unique across the RC 
    
   If any of these checks fail, the SG refuses the ASPAC request, with 
   an error, "Invalid loadsharing label." 
    
4.7.3 Routing and message distribution at the SG 

4.7.3.1 TCAP traffic 
    
   Messages not containing a destination (or "responding") TID, i.e. 
   Query, Begin, Unidirectional, are loadshared among the available 
   ASPs. Any scheme permitting a fair load distribution among the ASPs 
   is allowed (e.g. round robin). 
    
   When a destination TID is present, the SG extracts the label and 
   selects the ASP that corresponds with it. 
    
   If an ASP is not available, the SG may generate (X)UDTS "routing 
   failure", if the return option is used.  

4.7.3.2 SCCP Connection Oriented traffic 
    
   Messages not containing a destination reference number (DRN), i.e. a 
   Connection Request, MAY be loadshared among the available ASPs. The 
   load distribution mechanism is an implementation issue. When a DRN is 
   present, the SG extracts the label and selects the ASP that 
   corresponds with it. If an ASP is not available, the SG discards the 
   message. 
    
4.7.4 Multiple SGs, SUA Relay Function 
    
   It is important that each ASP send its unique label (within the AS) 
   to each SGP. For a better robustness against association failures, 
   the SGs MAY cooperate to provide alternative routes towards an ASP. 
   Mechanisms for SG cooperation/co-ordination are outside of the scope 
   of this document. 
    
5 Examples of SUA Procedures 
 
   The following sequence charts overview the procedures of SUA.  These 
   are meant as examples, they do not, in and of themselves, impose 
   additional requirements upon an instance of SUA. 
    
5.1 SG Architecture 
 
   The sequences below outline logical steps for a variety of scenarios 
   within a SG architecture.  Please note that these scenarios cover a 
   Primary/Backup configuration.  Where there is a load-sharing 
   configuration then the SGP can declare availability when 1 ASP 

 
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   issues ASPAC but can only declare unavailability when all ASPs have 
   issued ASPIA. 
    
5.1.1 Establishment of SUA connectivity 
 
   The following is established before traffic can flow. 
    
   Each node is configured (via MIB, for example) with the connections 
   that need to be setup. 
    
        ASP-a1            ASP-a2                SG                  SEP 
       (Primary)           (Backup)                                       
          |------Establish SCTP Association------| 
                             |--Estab. SCTP Ass--| 
                                                 |--Align SS7 link---| 
          +----------------ASP Up----------------> 
          <--------------ASP Up Ack--------------+ 
                             +------ASP Up-------> 
                             <---ASP Up Ack------+ 
          +-------------ASP Active---------------> 
          <----------ASP Active Ack--------------+ 
          <----------NTFY (ASP Active)-----------+ 
                             <-NTFY (ASP Active)-+ 
                                                 +--------SSA--------> 
                                                 <--------SSA--------+ 
          <-----------------DAVA-----------------+ 
          +-----------------CLDT-----------------> 
                                                 +--------UDT--------> 
    
5.1.2 Failover scenarios 
    
   The following sequences address failover of SEP and ASP 
    
5.1.2.1 SEP Failover 
    
   The SEP knows that the SGP is 'concerned' about its availability.  
   Similarly, the SGP knows that ASP-a1 is concerned about the SEPs 
   availability; therefore the incoming SSP is translated into DUNA.  
   ASP-a1 uses a DAUD to instruct the SGP to invoke the SS7 Sub-system 
   Test procedure. 
    
        ASP-a1            ASP-a2                SG                  SEP 
      (Primary)           (Backup)                                       
                                                 <--------SSP--------+ 
          <-----------------DUNA-----------------+ 
          +-----------------DAUD-----------------> 
                                                 +--------SST--------> 
 
5.1.2.2 Successful ASP Failover scenario 
    
   The following is an example of a successful failover scenario, where 
   there is a failover from ASP-a1 to ASP-a2, i.e. Primary to Backup.  
 
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   During the failover, the SGP buffers any incoming data messages from 
   the SEP, forwarding them when the Backup becomes available. 
    
        ASP-a1            ASP-a2                SG                  SEP 
      (Primary)           (Backup)                                       
          +-------------ASP Inactive-------------> 
          <----------NTFY (ASP Inactive)---------+ 
                             <-NTFY (ASP Inact.)-+ 
                             +----ASP Active-----> 
                             <--ASP Active Ack---+ 
                             <-NTFY (ASP Active)-+ 
          <----------NTFY (ASP Active)-----------+ 
    
5.1.2.3 Unsuccessful ASP Failover scenario 
 
        ASP-a1            ASP-a2                SG                  SEP 
      (Primary)           (Backup)                                       
          +-------------ASP Inactive-------------> 
          <----------NTFY (ASP Inactive)---------+ 
                             <-NTFY (ASP Inact.)-+ 
                After some time elapses (i.e. timeout). 
                                                 +--------SSP--------> 
                                                 <--------SST--------+ 
                                                  
5.2 IPSP Examples. 
 
   The sequences below outline logical steps for a variety of scenarios 
   within an IP-IP architecture.  Please note that these scenarios 
   cover a Primary/Backup configuration.  Where there is a load-sharing 
   configuration then the AS can declare availability when 1 ASP issues 
   ASPAC but can only declare unavailability when all ASPs have issued 
   ASPIA. 
    
5.2.1 Establishment of SUA connectivity 
    
   The following shows an example establishment of SUA connectivity.  
   In this example, each IPSP consists of an Application Server and two 
   ASPs.  The following is established before SUA traffic can flow. A 
   connectionless flow is shown for simplicity. 
    
   Establish SCTP Connectivity - as per RFC 2960. Note that SCTP 
   connections are bi-directional. The endpoint that establishes SCTP 
   connectivity MUST also establishes UA connectivity (see RFC 2960, 
   section 5.2.1 for handling collisions) [2960]. 
    

 
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   IP SEP A                                                  IP SEP B 
   AS A                                                          AS B 
   ASP-a1     ASP-a2                                 ASP-b2    ASP-b1 
    
   [All ASPs are in the ASP-DOWN state] 
                  
   +-------------------------------ASP Up-------------------------->  
   <-----------------------------ASP Up Ack------------------------+ 
    
                 +--------------ASP Up---------------> 
                 <------------ASP Up Ack-------------+ 
    
   +---------------------------ACTIVE-------------------------------> 
   <-------------------------ACTIVE Ack-----------------------------+ 
    
   [Traffic can now flow directly between ASPs] 
    
   +-----------------------------CLDT-------------------------------> 
    
5.2.2 Failover scenarios 
    
   The following sequences address failover of ASP 

5.2.2.1 Successful ASP Failover scenario 
    
   The following is an example of a successful failover scenario, where 
   there is a failover from ASP-a1 to ASP-a2, i.e. Primary to Backup.  
   Since data transfer passes directly between peer ASPs, ASP-b1 is 
   notified of the failover of ASP-a1 and buffers outgoing data 
   messages until ASP-a2 becomes available. 
    
   IP SEP A                                                  IP SEP B 
   ASP-a1     ASP-a2                                 ASP-b2    ASP-b1 
    
   +-----------------------------ASP Inact------------------------> 
   <---------------------------ASP Inact Ack----------------------+ 
              <---------------NTFY (ASP-a1 Inactive)--------------+ 
              +---------------------ASP Act-----------------------> 
              <-------------------ASP Act Ack---------------------+ 

5.2.2.2 Unsuccessful ASP Failover scenario 
    
   The sequence is the same as 5.2.2.1 except that, since the backup 
   fails to come in then, the Notify messages declaring the 
   availability of the backup are not sent. 
    
6 Security Considerations 
    
6.1 Introduction 
    

 
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   SUA is designed to carry signalling messages for telephony services. 
   As such, SUA involves the security needs of several parties: the end 
   users of the services; the network providers and the applications 
   involved.  Additional security requirements may come from local 
   regulation.  While having some overlapping security needs, any 
   security solution should fulfill all of the different parties' 
   needs.  
 
6.2 Threats 
    
   There is no quick fix, one-size-fits-all solution for security.  As 
   a transport protocol, SUA has the following security objectives:
    
    * Availability of reliable and timely user data transport. 
    * Integrity of user data transport. 
    * Confidentiality of user data. 
    
   SUA runs on top of SCTP.  SCTP provides certain transport related 
   security features, such as: 
    
    * Blind Denial of Service Attacks 
    * Flooding 
    * Masquerade 
    * Improper Monopolization of Services 
    
   When SUA is running in professionally managed corporate or service 
   provider network, it is reasonable to expect that this network 
   include an appropriate security policy framework. The "Site Security 
   Handbook" [2196] should be consulted for guidance. 
    
   When the network in which SUA runs in involves more than one party, 
   it may not be reasonable to expect that all parties have implemented 
   security in a sufficient manner. End-to-end security should be the 
   goal; therefore, it is recommended that IPSEC be used to ensure 
   confidentiality of user payload.  Consult [2409] for more 
   information on configuring IPSEC services. 
    
6.3 Protecting Confidentiality  
    
   Particularly for mobile users, the requirement for confidentiality 
   may include the masking of IP addresses and ports.  In this case 
   application level encryption is not sufficient; IPSEC ESP should be 
   used instead. Regardless of which level performs the encryption, the 
   IPSEC ISAKMP service should be used for key management. 
    
7 IANA Considerations 
 
7.1 SCTP Payload Protocol ID 
    
   IANA has assigned a SUA value for the Payload Protocol Identifier in 
   the SCTP DATA chunk.  The following SCTP Payload Protocol Identifier 
   is registered: 
 
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           SUA    "4" 
    
   The SCTP Payload Protocol Identifier value "4" SHOULD be included in 
   each SCTP DATA chunk, to indicate that the SCTP is carrying the SUA 
   protocol. The value "0" (unspecified) is also allowed but any other 
   values MUST not be used.  This Payload Protocol Identifier is not 
   directly used by SCTP but MAY be used by certain network entities to 
   identify the type of information being carried in a DATA chunk. 
    
   The User Adaptation peer MAY use the Payload Protocol Identifier, as 
   a way of determining additional information about the data being 
   presented to it by SCTP.A request will be made to IANA to assign CTP 
   Payload Protocol IDs.   
    
7.2 Port Number 
    
   IANA has registered SCTP Port Number 14001 for SUA.  It is 
   recommended that SGPs use this SCTP port number for listening for 
   new connections.  SGPs MAY also use statically configured SCTP port 
   numbers instead. 
    
7.3 Protocol Extensions 
    
   This protocol may also be extended through IANA in three ways: 
    
    - Through definition of additional message classes. 
    - Through definition of additional message types. 
    - Through definition of additional message parameters. 
    
   The definition and use of new message classes, types and parameters 
   is an integral part of SIGTRAN adaptation layers.  Thus, these 
   extensions are assigned by IANA through an IETF Consensus action as 
   defined in [RFC2434]. 
    
   The proposed extension MUST in no way adversely affect the general 
   working of the protocol. 
    
   A new registry will be created by IANA to allow the protocol to be 
   extended 
    
7.3.1 IETF Defined Message Classes 
    
   The documentation for a new message class MUST include the following 
   information: 
   (a) A long and short name for the message class; 
   (b) A detailed description of the purpose of the message class. 
    
7.3.2 IETF Defined Message Types 
    
   Documentation of the message type MUST contain the following 
   information: 
 
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   (a) A long and short name for the new message type; 
   (b) A detailed description of the structure of the message. 
   (c) A detailed definition and description of intended use of each 
      field within the message. 
   (d) A detailed procedural description of the use of the new message 
      type within the operation of the protocol. 
   (e) A detailed description of error conditions when receiving this 
      message type. 
    
   When an implementation receives a message type which it does not 
   support, it MUST respond with an Error (ERR) message, with an Error 
   Code = Unsupported Message Type. 
    
7.3.4 IETF-defined TLV Parameter Extension 
    
   Documentation of the message parameter MUST contain the following 
   information: 
    
   (a) Name of the parameter type. 
   (b) Detailed description of the structure of the parameter field.  
       This structure MUST conform to the general type-length-value  
       format described earlier in the document. 
   (c) Detailed definition of each component of the parameter value. 
   (d) Detailed description of the intended use of this parameter type, 
       and an indication of whether and under what circumstances 
       multiple instances of this parameter type may be found within  
       the same message type. 
    
8 Timer Values 
    
     Ta                                      2 seconds 
     Tr                                      2 seconds 
     T(ack)                                  2 seconds 
     T(ias)    Inactivity Send timer         7 minutes 
     T(iar)    Inactivity Receive timer      15 minutes 
     T(beat)   Heartbeat Timer               30 seconds 
    
9 Acknowledgements 
    
   The authors would like to thank (in alphabetical order) Javier 
   Pastor-Balbas, Martin Booyens, Klaus Gradischnig, Miguel A. Garcia, 
   Marja-Liisa Hamalainen, Sherry Karl, Markus Maanoja, Sandeep 
   Mahajan, Ken Morneault, Chirayu Patel, Michael Purcell, Michael 
   Tuexen, Al Varney, Tim Vetter, Antonio Villena, Ben Wilson, Michael 
   Wright and James Yu for their insightful comments and suggestions. 
    
10 Authors' Addresses 
    
   John Loughney 
   Nokia Research Center 
   PO Box 407 
 
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   FIN-00045 Nokia Group 
   Finland 
   EMail: john.Loughney@nokia.com 
    
   Greg Sidebottom 
   gregside consulting 
   Kanata, Ontario 
   Canada 
   EMail: gregside@home.com 
    
   Guy Mousseau 
   Nortel Networks 
   3685 Richmond Rd 
   Nepean, Ontario,  
   Canada K2H 5B7 
    
   Stephen Lorusso 
   Unisphere Networks 
   10 Technology Park Drive 
   Westford, MA  01886 
   USA 
   Phone: +1 (978) 589-0533 
   EMail: SLorusso@UnisphereNetworks.com 
    
   Lode Coene 
   Siemens Atea 
   Atealaan 34 
   B-2200 Herentals 
   Belgium 
   Phone: +32-14-252081 
   EMail: lode.coene@siemens.atea.be 
    
   Gery Verwimp 
   Siemens Atea 
   34 Atealaan 
   PO 2200 
   Herentals 
   Belgium 
   Phone: +32 14 25 3424 
   EMail: gery.verwimp@siemens.atea.be 
    
   Joe Keller 
   Tekelec 
   5200 Paramount Parkway 
   Morrisville, NC 27560 
   USA 
   EMail: joe.keller@tekelec.com 
    
   Florencio Escobar Gonzalez 
   Ericsson Spain S.A. 
   Retama 7, 2nd floor 
   28045, Madrid 
 
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   Spain 
   EMail: florencio.escobar@ericsson.com 
    
   Steven Furniss 
   Marconi 
   New Century Park 
   Coventry CV3 1HJ 
   United Kingdom 
   EMail: steven.furniss@marconi.com 
    
   William Sully 
   Marconi 
   New Century Park 
   Coventry CV3 1HJ 
   United Kingdom 
   EMail: william.sully@marconi.com 
    
   Brian Bidulock 
   OpenSS7 Corporation 
   4701 Preston Park Boulevard 
   Suite 424 
   Plano TX 75093 
   USA 
   EMail: bidulock@openss7.org 
    
11 References 
    
   Normative 
    
   [1123]         RFC 1123, "Requirements for Internet Hosts -- 
                  Application and Support" Braden, R. (Editor), October 
                  1989. 
     
   [2196]         RFC 2196, "Site Security Handbook", B. Fraser Ed., 
                  September 1997. 
    
   [2401]         RFC 2401, "Security Architecture for the Internet 
                  Protocol", S. Kent, R. Atkinson, November 1998. 
    
   [2960]         RFC 2960 "Stream Control Transport Protocol" R. 
                  Stewart, et al, November 2000. 
    
   [ANSI SCCP]    ANSI T1.112 'Signalling System Number 7 - Signalling 
                  Connection Control Part' 
   [ITU SCCP]     ITU-T Recommendations Q.711-714, 'Signalling System 
                  No. 7 (SS7) - Signalling Connection Control Part 
                  (SCCP)' 
    
   Non-Normative 
    

 
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   [2434]         RFC 2434, "Guidelines for Writing an IANA 
                  Considerations Section in RFCs", T. Narten, H. 
                  Alvestrand, October 1998. 
    
   [2719]         RFC 2719, "Framework Architecture for Signaling 
                  Transport" 
    
   [2916]         RFC 2916, "E.164 number and DNS", P. Faltstrom, 
                  September 2000. 
    
   [ANSI-MTP]     ANSI T1.111 'Signalling System Number 7 - Message 
                  Transfer Part' 
    
   [ANSI TCAP]    ANSI T1.114 'Signalling System Number 7 - Transaction 
                  Capabilities Application Part' 
    
   [ITU-MTP]      ITU-T Recommendations Q.701-Q.705, 'Signalling System 
                  No. 7 (SS7) - Message Transfer Part (MTP)' 
     
   [ITU TCAP]     ITU-T Recommendation Q.771-775 'Signalling System No. 
                  7 SS7) - Transaction Capabilities (TCAP) 
    
   [M3UA]         MTP3-User Adaptation Layer <draft-ietf-sigtran-m3ua-
                  10.txt>, November 2001, Work in Progress. 
 
   [RANAP]        3G TS 25.413 V3.5.0 (2001-03) 'Technical 
                  Specification 3rd Generation Partnership Project; 
                  Technical Specification Group Radio Access Network; 
                  UTRAN Iu Interface RANAP Signalling' 
    
   [UTRAN IUR]    3G TS 25.422 V3.5.0 (2000-12) "Technical 
                  Specification 3rd Generation Partnership Project; 
                  Technical Specification Group Radio Access Network; 
                  UTRAN Iur Interface Signalling Transport (Release 
                  1999)" 
    
Appendix A Signaling Network Architecture 
    
A.1 Generalized Peer-to-Peer Network Architecture 
    
   Figure 1 shows an example network architecture that can support 
   robust operation and failover.  There need to be some management 
   resources at the AS to manage traffic. 

 
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         *********** 
         *   AS1   * 
         * +-----+ * SCTP Associations 
         * |ASP1 +-------------------+ 
         * +-----+ *                 |                   *********** 
         *         *                 |                   *   AS3   * 
         * +-----+ *                 |                   * +-----+ * 
         * |ASP2 +-----------------------------------------+ASP1 | * 
         * +-----+ *                 |                   * +-----+ * 
         *         *                 |                   *         * 
         * +-----+ *                 |                   * +-----+ * 
         * |ASP3 | *            +--------------------------+ASP2 | * 
         * +-----+ *            |    |                   * +-----+ * 
         ***********            |    |                   *********** 
                                |    | 
         ***********            |    |                   *********** 
         *   AS2   *            |    |                   *   AS4   * 
         * +-----+ *            |    |                   * +-----+ * 
         * |ASP1 +--------------+    +---------------------+ASP1 | * 
         * +-----+ *                                     * +-----+ * 
         *         *                                     *         * 
         * +-----+ *                                     * +-----+ * 
         * |ASP2 +-----------------------------------------+ASP1 | * 
         * +-----+ *                                     * +-----+ * 
         *         *                                     *********** 
         * +-----+ * 
         * |ASP3 | * 
         * +-----+ * 
         *         * 
         *********** 
    
   Figure 1: Generalized Architecture 
    
   In this example, the Application Servers are shown residing within 
   one logical box, with ASPs located inside.  In fact, an AS could be 
   distributed among several hosts.  In such a scenario, the host 
   should share state as protection in the case of a failure.  This is 
   out of scope of this protocol. Additionally, in a distributed 
   system, one ASP could be registered to more than one AS.  This draft 
   should not restrict such systems - though such a case in not 
   specified. 
    
A.2 Signalling Gateway Network Architecture 
    
   When interworking between SS7 and IP domains is needed, the SGP acts 
   as the gateway node between the SS7 network and the IP network.  The 
   SGP will transport SCCP-user signalling traffic from the SS7 network 
   to the IP-based signalling nodes (for example IP-resident 
   Databases). The Signalling Gateway can be considered as a group of 
   Application Servers with additional functionality to interface 
   towards an SS7 network. 
 
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Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
    
   The SUA protocol should be flexible enough to allow different 
   configurations and transport technology to allow the network 
   operators to meet their operation, management and performance 
   requirements.  
    
   An ASP may be connected to multiple SGPs (see figure 2). In such a 
   case, a particular SS7 destination may be reachable via more than 
   SG, therefore, more than one route. Given that proper SLS selection, 
   loadsharing, and SG selection based on point code availability is 
   performed at the ASP, it will be necessary for the ASP to maintain 
   the status of each distant SGPs to which it communicates on the 
   basis of the SG through which it may route.  
    
   Signalling Gateway 
                            SCTP Associations 
      +----------+                                       ************** 
      | SG1      |                                       *  AS3       * 
      | ******** |                                       *  ********  *  
      | * SGP11+--------------------------------------------+ ASP1 *  * 
      | ******** |                                 /     *  ********  * 
      | ******** |                                 |     *  ********  * 
      | * SGP12+--------------------------------------------+ ASP2 *  * 
      | ******** |                   \           / |     *  ********  * 
      +----------+                    \          | |     *      .     * 
                                       \         | |     *      .     * 
      +----------                       \        | |     *      .     * 
      | SG2      |                       \       | |     *      .     * 
      | ******** |                        \      | |     *  ********  *  
      | * SGP21+---------------------------------+-*  * ASPN *  * 
      | ******** |                          \            *  ********  * 
      | ******** |                           \           ************** 
      | * SGP22+---+--+                       \                
      | ******** | |  |                        \         ************** 
      +----------+ |  |                         \        *  AS4       * 
                   |  |                          \       *  ********  *   
                   |  +-------------------------------------+ ASP1 *  * 
                   |                                     *  ********  * 
                   |                                     *      .     * 
                   |                                     *      .     * 
                   |                                     *            * 
                   |                                     *  ********  * 
                   +----------------------------------------+ ASPn *  * 
                                                         *  ********  * 
                                                         ************** 
    
                Figure 2: Signalling Gateway Architecture 
    
   The pair of SGs can either operate as replicated endpoints or as 
   replicated relay points from the SS7 network point of view.  
    

 
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   Replicated endpoints: the coupling between the SGs and the ASPs when 
   the SGs act as replicated endpoints is an implementation issue.  
    
   Replicated relay points: in normal circumstances, the path from SEP 
   to ASP will always go via the same SGP when in-sequence-delivery is 
   requested.  However, linkset failures may cause MTP to re-route to 
   the other SG. 
    
A.3 Signaling Gateway Message Distribution Recommendations 
 
A.3.1 Connectionless Transport 
    
   By means of configuration, the SG knows the local SCCP-user is 
   actually represented by an AS, and serviced by a set of ASPs working 
   in n+k redundancy mode.  An ASP is selected and a CLDT message is 
   sent on the appropriate SCTP association/stream. 
    
   The selection criterion can be based on a round robin mechanism, or 
   any other method that guarantees a balanced load sharing over the 
   active ASPs. However, when TCAP messages are transported, load 
   sharing is only possible for the first message in a TCAP dialogue 
   (TC_Begin, TC_Query, TC_Unidirectional). All other TCAP messages in 
   the same dialogue are sent to the same ASP that was selected for the 
   first message, unless the ASPs are able to share state and maintain 
   in sequence delivery. To this end, the SGP needs to know the TID 
   allocation policy of the ASPs in a single AS: 
    
     -    State sharing 
     -    Fixed range of TIDs per ASP in the AS 
    
   This information may be preconfigured in the SG, or may be 
   dynamically exchanged via the ASP_Active message. 
    
   An example for an INAP/TCAP message exchange between SEP and ASP is 
   given below.  
    
   Address information in CLDT message (e.g. TC_Query) from SGP to ASP, 
   with association ID = SG-ASP, Stream ID based on sequence control 
   and possibly other parameters, e.g. OPC: 
    
     -  Routing Context: based on SS7 Network ID and AS membership, so 
        that the message can be transported to the correct ASP. 
     -  Source address: valid combination of SSN, PC and GT, as needed 
        for back routing to the SEP. 
     -  Destination address: at least SSN, to select the SCCP/SUA-user 
        at the ASP. 
    
   Address information in CLDT message (e.g. TC_Response) from ASP to 
   SG, with association ID = ASP-SG, stream ID selected by 
   implementation dependent means with regards to in-sequence-delivery: 
    
     -  Routing Context: as received in previous message. 
 
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     -  Source address: unique address provided so that when used as 
        the SCCP called party address in the SEP, it must yield the 
        same AS, the SSN might be sufficient. 
     -  Destination address: copied from source address in received   
        CLDT message. 
    
   Further messages from the SEP belonging to the same TCAP transaction 
   will now reach the same ASP. 
    
A.3.2 Connection-Oriented Transport 
 
   Further messages for this connection are routed on DPC in the SS7 
   connection section (MTP routing label), and on IP address in the IP 
   connection section (SCTP header).  No other routing information is 
   present in the SCCP or SUA messages themselves. Resources are kept 
   within the SG to forward messages from one section to another and to 
   populate the MTP routing label or SCTP header, based on the 
   destination local reference of these messages (Connect Confirm, Data 
   Transfer, etc.) 
    
   This means that in the SG, two local references are allocated, one 
   3-byte value used for the SS7 section and one 4-byte value for the 
   IP section. Also a resource containing the connection data for both 
   sections is allocated, and either of the two local references can be 
   used to retrieve this data e.g. for an incoming DT1 or CODT, for 
   example. 
    
Copyright Statement 
    
   Copyright (C) The Internet Society (2001). All Rights Reserved. 
    
   This document and translations of it may be copied and furnished to 
   others, and derivative works that comment on or otherwise explain it 
   or assist in its implementation may be prepared, copied, published 
   and distributed, in whole or in part, without restriction of any 
   kind, provided that the above copyright notice and this paragraph 
   are included on all such copies and derivative works. However, this 
   document itself may not be modified in any way, such as by removing 
   the copyright notice or references to the Internet Society or other 
   Internet organizations, except as needed for the purpose of 
   developing Internet standards in which case the procedures for 
   copyrights defined in the Internet Standards process must be 
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   The limited permissions granted above are perpetual and will not be 
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   This document and the information contained herein is provided on an 
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 
 
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Internet Draft       SS7 SCCP-User Adaptation Layer  December 27, 2001 
 
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 
 

 
Loughney (editor)                                           [Page 114] 
 



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