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draft-ietf-sigtran-sua-implementor-guide-02

Description: Request For Comments

You can download source copies of the file as follows:

draft-ietf-sigtran-sua-implementor-guide-02.txt in text format.

Listed below is the contents of file draft-ietf-sigtran-sua-implementor-guide-02.txt.




Signalling Transport Working group                              L. Coene
Internet-Draft                                                   Siemens
Expires: April 24, 2006                                      J. Loughney
                                                                   Nokia
                                                        October 21, 2005

                        SUA Implementor's guide
           <draft-ietf-sigtran-sua-implementor-guide-02.txt>

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   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 Internet-Draft will expire on April 24, 2006.

Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This document contains a compilation of all defects found up until
   the publication date for SUA [RFC3868] [1].  These defects may be of
   an editorial or technical nature.  This document may be thought of as
   a companion document to be used in the implementation of SUA to
   clarify errors in the original SUA document.  This document updates
   RFC3868 and text within this document supersedes the text found in
   RFC3868.

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Table of Contents

   1.  INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
     1.2.  Conventions  . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Correction to RFC3868  . . . . . . . . . . . . . . . . . . . .  5
     2.1.  Routing context list in connectionless and
           connectionoriented messages  . . . . . . . . . . . . . . .  5
       2.1.1.  Description of the problem . . . . . . . . . . . . . .  5
       2.1.2.  Text changes to the document . . . . . . . . . . . . .  5
       2.1.3.  Solution description . . . . . . . . . . . . . . . . .  5
     2.2.  Congestion level parameter value . . . . . . . . . . . . .  5
       2.2.1.  Description of the problem . . . . . . . . . . . . . .  5
       2.2.2.  Text changes to the document . . . . . . . . . . . . .  6
       2.2.3.  Solution description . . . . . . . . . . . . . . . . .  7
     2.3.  Segmentation parameter value . . . . . . . . . . . . . . .  7
       2.3.1.  Description of the problem . . . . . . . . . . . . . .  7
       2.3.2.  Text changes to the document . . . . . . . . . . . . .  7
       2.3.3.  Solution description . . . . . . . . . . . . . . . . .  8
     2.4.  DAUD response message ordering . . . . . . . . . . . . . .  8
       2.4.1.  Description of the problem . . . . . . . . . . . . . .  8
       2.4.2.  Text changes to the document . . . . . . . . . . . . .  8
       2.4.3.  Solution description . . . . . . . . . . . . . . . . .  9
     2.5.  Host name parameter  . . . . . . . . . . . . . . . . . . .  9
       2.5.1.  Description of the problem . . . . . . . . . . . . . .  9
       2.5.2.  Text changes to the document . . . . . . . . . . . . .  9
       2.5.3.  Solution description . . . . . . . . . . . . . . . . . 10
     2.6.  ASP routing context  . . . . . . . . . . . . . . . . . . . 10
       2.6.1.  Description of the problem . . . . . . . . . . . . . . 10
       2.6.2.  Text changes to the document . . . . . . . . . . . . . 10
       2.6.3.  Solution description . . . . . . . . . . . . . . . . . 10
     2.7.  Parameters should only occur once in a message . . . . . . 11
       2.7.1.  Description of the problem . . . . . . . . . . . . . . 11
       2.7.2.  Text changes to the document . . . . . . . . . . . . . 11
       2.7.3.  Solution description . . . . . . . . . . . . . . . . . 11
     2.8.  TID label parameter  . . . . . . . . . . . . . . . . . . . 11
       2.8.1.  Description of the problem . . . . . . . . . . . . . . 11
       2.8.2.  Text changes to the document . . . . . . . . . . . . . 12
       2.8.3.  Solution description . . . . . . . . . . . . . . . . . 13
     2.9.  DRM label parameter  . . . . . . . . . . . . . . . . . . . 13
       2.9.1.  Description of the problem . . . . . . . . . . . . . . 13
       2.9.2.  Text changes to the document . . . . . . . . . . . . . 13
       2.9.3.  Solution description . . . . . . . . . . . . . . . . . 14
     2.10. Usage of the TID and DRN label . . . . . . . . . . . . . . 14
       2.10.1. Description of the problem . . . . . . . . . . . . . . 14
       2.10.2. Text changes to the document . . . . . . . . . . . . . 15
       2.10.3. Solution description . . . . . . . . . . . . . . . . . 17
     2.11. Address Range paramete . . . . . . . . . . . . . . . . . . 18

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       2.11.1. Description of the problem . . . . . . . . . . . . . . 18
       2.11.2. Text changes to the document . . . . . . . . . . . . . 18
       2.11.3. Solution description . . . . . . . . . . . . . . . . . 19
     2.12. Interpretation of the mask parameter . . . . . . . . . . . 19
       2.12.1. Description of the problem . . . . . . . . . . . . . . 19
       2.12.2. Text changes to the document . . . . . . . . . . . . . 19
       2.12.3. Solution description . . . . . . . . . . . . . . . . . 20
     2.13. Reply on errors contained in a error message . . . . . . . 20
       2.13.1. Description of the problem . . . . . . . . . . . . . . 20
       2.13.2. Text changes to the document . . . . . . . . . . . . . 20
       2.13.3. Solution description . . . . . . . . . . . . . . . . . 21
     2.14. Use of stream 0 for SSNM messages  . . . . . . . . . . . . 21
       2.14.1. Description of the problem . . . . . . . . . . . . . . 21
       2.14.2. Text changes to the document . . . . . . . . . . . . . 21
       2.14.3. Solution description . . . . . . . . . . . . . . . . . 22
     2.15. Timer Ta does not exist  . . . . . . . . . . . . . . . . . 22
       2.15.1. Description of the problem . . . . . . . . . . . . . . 22
       2.15.2. Text changes to the document . . . . . . . . . . . . . 22
       2.15.3. Solution description . . . . . . . . . . . . . . . . . 23
     2.16. Error response on unsupported RKM messages . . . . . . . . 23
       2.16.1. Description of the problem . . . . . . . . . . . . . . 23
       2.16.2. Text changes to the document . . . . . . . . . . . . . 23
       2.16.3. Solution description . . . . . . . . . . . . . . . . . 24
     2.17. Filler/padding in Global title parameter . . . . . . . . . 24
       2.17.1. Description of the problem . . . . . . . . . . . . . . 24
       2.17.2. Text changes to the document . . . . . . . . . . . . . 24
       2.17.3. Solution description . . . . . . . . . . . . . . . . . 25
     2.18. Inclusion of routing context in the Routing key
           parameter  . . . . . . . . . . . . . . . . . . . . . . . . 25
       2.18.1. Description of the problem . . . . . . . . . . . . . . 25
       2.18.2. Text changes to the document . . . . . . . . . . . . . 26
       2.18.3. Solution description . . . . . . . . . . . . . . . . . 27
   3.  Security considerations  . . . . . . . . . . . . . . . . . . . 28
   4.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 29
   5.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
   Appendix A.  Changes Control . . . . . . . . . . . . . . . . . . . 30
     A.1.  Changes from v00 to v01  . . . . . . . . . . . . . . . . . 30
     A.2.  Changes from v01 to v02  . . . . . . . . . . . . . . . . . 30
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31
   Intellectual Property and Copyright Statements . . . . . . . . . . 32

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1.  INTRODUCTION

   This document contains a compilation of all defects found up until
   the publication date for the SCCP User Adaptation Layer (SUA)
   [RFC3868].  These defects may be of an editorial or technical nature.
   This document may be thought of as a companion document to be used in
   the implementation of SUA to clarify errors in the original SUA
   document.  This document updates RFC3868 and text within this
   document, where noted, supersedes the text found in RFC3868.  Each
   error will be detailed within this document in the form of:

   o  The problem description,

   o  The text quoted from RFC3868,

   o  The replacement text,

   o  A description of the solution.

1.1.  Terminology

   The terms are commonly identified in related work SUA [RFC3868] [1].

1.2.  Conventions

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2.  Correction to RFC3868

2.1.  Routing context list in connectionless and connectionoriented
      messages

2.1.1.  Description of the problem

   The routing context parameter of a connectionless and
   connectionoriented message can contain a list of routing contexts.
   Normaly, the addressing info present in the message will yield only a
   single routing context.  A list of routing contexts is valid only for
   SSNM, ASPTM and RKM messages

2.1.2.  Text changes to the document

   ---------
   Old text: (Section 3.9.6)
   ---------

   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.

   ---------
   New text: (Section 3.9.6)
   ---------

   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.

   A list of routing contexts is only valid for SSNM, ASPTM and RKM
   messages.  All other messages can contain only a single Routing
   Context.

2.1.3.  Solution description

   Only 1 routing context value may be included in the routing context
   parameter of a connectionless and connectionoriented message.

2.2.  Congestion level parameter value

2.2.1.  Description of the problem

   The value of the congestion level is dependant on which info is
   present in the SCON message.  If the SCON only contains the affected

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   pointcode, then the congestion level has values ranging between 0 and
   3.  If affected pointcode and subsystemnumber is included in the SCON
   message, then the value of the congestion level can be between 1 and
   8.

2.2.2.  Text changes to the document

   ---------
   Old text: (Section 3.10.24)
   ---------

   When the Congestion Level parameter is included in a SCON message
   that corresponds to an N-PCSTATE primitive, the Congestion Level
   field indicates the MTP congestion level experienced by the local or
   affected signalling point as indicated by the Affected Point Code(s)
   also in the SCON message.  In this case, valid values for the
   Congestion Level field are as follows:

        0  No Congestion or Undefined
        1  Congestion Level 1
        2  Congestion Level 2
        3  Congestion Level 3

   When the Congestion Level parameter is included in a SCON messagethat
   corresponds to an N-STATE primitive, the Congestion Level field
   indicates the SCCP restricted importance level experienced by the
   local or affected subsystem as indicated by the Affected Point Code
   and Subsystem Number also in the SCON message.  In this case, valid
   values for the Congestion Level field range from 0 to 7, where 0
   indicates the least congested and 7 indicates the most congested
   subsystem.

   ---------
   New text: (Section 3.10.24)
   ---------

   2 different congestion levels ranges can be used accoring to ITU and
   ANSI congestion control algorithms.

   When the ANSI congestion control algorithm is used, the Congestion
   Level field indicates the MTP congestion level as experienced by the
   local or affected subsystem indicated by the Affected Point Code and
   Subsystem Number.  In this case, valid values for the Congestion
   Level field range from 0 to 3, where 1 indicates the least congested
   and 3 indicates the most congested condition.

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        0  No Congestion or Undefined
        1  Congestion Level 1
        2  Congestion Level 2
        3  Congestion Level 3

   When the ITU congestion control algorithm is used, the Congestion
   Level field indicates the SCCP restricted importance level
   experienced by the local or affected subsystem as indicated by the
   Affected Point Code and Subsystem Number also in the SCON message.
   In this case, valid values for the Congestion Level field range from
   1 to 8, where 1 indicates the least congested and 8 indicates the
   most congested condition.

2.2.3.  Solution description

   The ITU SCCP congestion control procedures are described in SCCP
   procedures [Q.714] [4] paragraph 2.6.  The ANSI SCCP congestion
   control procedures are described in SCCP procedures [T1.112.4] [5]
   paragraph 5.2.4.

   The SCC message in SCCP takes the value range 1..8, so the
   corresponding SCON should also be in that range.  To indicate no
   congestion, it is sufficient to send only a DAVA.

2.3.  Segmentation parameter value

2.3.1.  Description of the problem

   The original sequence delivery option as original demanded(= before
   the segementing) by the SCCP application is not preserved after
   segmentation.  The receiving SCCP application will always receive the
   message with sequenced delivery option set to 1.

2.3.2.  Text changes to the document

   ---------
   Old text: (Section 3.10.23)
   ---------

   The first/remaining segments field is formatted as follows:

   o  bit 8 (MSB) : indicates whether this is the first segment (1) or
      not (0)

   o  bits 1-7: indicate the number of remaining segments, value between
      0 and 15

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   ---------
   New text: (Section 3.10.23)
   ---------

   The segmentation paramter consists of the following:

   o  bit 0: first/remaing segment bit: first = 1, remaining = 0

   o  bit 1: sequence delivery option as original demanded(= before the
      segementing) by the SCCP application. class 0 = 0, class 1 = 1.

   o  bit 2-3: spare

   o  bit 4-7: number of remaining segments(4 bits, values 0 -15)

   o  bit 8-31:segmentation reference(3 byte integer)

2.3.3.  Solution description

   The segmentation parameter gets a extra bit(out of the spare bits
   present) indicating the original requested sequence delivery option
   as originally demanded by the sending SCCP application.

2.4.  DAUD response message ordering

2.4.1.  Description of the problem

   Should a SCON be send before the DAVA or DRST or after?  The SCON is
   send first and DAVA/DRST after in M3UA.

2.4.2.  Text changes to the document

   ---------
   Old text: (Section 4.5.3)
   ---------

   The SGP SHOULD respond to a DAUD message with the availability and
   congestion status of the subsystem.  The status of each SS7
   destination or subsystem 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 or
   subsystem is available and congested, the SGP responds with an SCON
   message in addition to the DAVA message.  If the SS7 destination or
   subsystem 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 or
   subsystem, the SGP responds with a DUNA message, as it has no routing
   information to allow it to route traffic to this destination or

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   subsystem.

   ---------
   New text: (Section 4.5.3)
   ---------

   The SGP SHOULD respond to a DAUD message with the availability and
   congestion status of the subsystem.  The status of each SS7
   destination or subsystem 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 or
   subsystem is available and congested, the SGP responds with an SCON
   message and a DAVA message.  If the SS7 destination or subsystem is
   restricted and congested, the SGP responds with an SCON message and a
   DRST.  If the SGP has no information on the availability / congestion
   status of the SS7 destination or subsystem, the SGP responds with a
   DUNA message, as it has no routing information to allow it to route
   traffic to this destination or subsystem.

2.4.3.  Solution description

   The DAVA/DUNA/DRST/SCON messages may be send in random order.
   However if a SCON is send first and the destination is inaccessible,
   the SCON will be dropped.  So it might be better to send the DAVA
   first followed by the SCON.

2.5.  Host name parameter

2.5.1.  Description of the problem

   The hostname is actually a Fully Qualified Domain Name(FQDN) as
   defined in RFC1983.  The definition of the hostname(as found in
   RFC1983) would only allow for a part of the FQDN and that does not
   uniquely identify a endpoint.  Also the encoding of the FQDN is not
   clear.

2.5.2.  Text changes to the document

   ---------
   Old text: (Section 3.10.2.7)
   ---------

   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.

   ---------
   New text: (Section 3.10.2.7)

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   ---------

   This field contains a host name in "Fully Qualified Domain Name
   syntax" per RFC 1035 section 3.1 [RFC1035] [3].  The method for
   resolving the host name is out of scope for this document.

2.5.3.  Solution description

   The hostname is actually a Fully Qualified Domain Name(FQDN) which
   should be encoded following the RFC1035 section 3.1 coding rules.

2.6.  ASP routing context

2.6.1.  Description of the problem

   An ASP routes responses to the SGP that it received messages from;
   within the routing context which it is currently active and receiving
   traffic.

2.6.2.  Text changes to the document

   ---------
   Old text: (Section 1.5.2)
   ---------

   An ASP routes responses to the SGP that it received messages from;
   within the routing context which it is currently active and receiving
   traffic.

   ---------
   New text: (Section 1.5.2)
   ---------

   An ASP routes responses to the SGP that it received messages from.
   The reponse will utilize the routing context from the received
   messages.

2.6.3.  Solution description

   a.  A routing context is an integer which is significant only for a
   given SGP-ASP pair.  So it is circular logic to say that the ASP
   should use the RC to select the SGP - an RC value is meaningful only
   after the SGP has already assigned the RC for the the msg send to the
   ASP.

   b.  An ASP can be active vis-a-vis an SGP for more than one RC - so
   it is not meaningful to say that the ASP uses "the" RC for which it
   is active.  If the ASP response to a messages, it has to use the RC

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   of that received message in the reponse.

2.7.  Parameters should only occur once in a message

2.7.1.  Description of the problem

   Parameters in SUA messages can be repeated as many times as possible.
   This would lead to inconsistencies, such as 2 or more destination
   addresses.

2.7.2.  Text changes to the document

   ---------
   Old text: (Section x.x)
   ---------

   ---------
   New text: (Section x.x)
   ---------

2.7.3.  Solution description

   Unless explicitly stated or shown in a message format diagram, only
   one parameter of the same type is allowed in a message.

2.8.  TID label parameter

2.8.1.  Description of the problem

   The clarity of the definition of TID label parameters is unclear.

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2.8.2.  Text changes to the document

   ---------
   Old text: (Section 3.10.16)
   ---------
       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 = 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 integer, which is unique across an AS.

   ---------
   New text: (Section 3.10.16)
   ---------
       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 = 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 integer, which is unique across an AS. The
      label value has to match the TCAP transaction ID between the start
      and the end parameter(Logical AND operation). The rest of the TCAP
      transaction ID between 0 and the begin parameter(if begin parameter
       > 0) AND the end parameter(if end parameter value < 31) and 31 is
      wildcarded.
      An ASP that registers a label will be sent only those TID-bearing
      messages that match its label.
      An ASP that does not register a label may be sent any TID-bearing
      message.

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2.8.3.  Solution description

   The clarity of the definition of the TID and DRM label parameters is
   improved by adding what should be wildcarded in the TID/DRM and how
   to use the start and end field.  It is assumed that these labels are
   simple values(at a certain location) that are logical ANDed(taking
   into account the start and end position where to apply) onto the
   received TID or DRN.  If the result of the AND operation exactly
   matches the "Label" field, then the message is sent to the ASP that
   registered for this label via the ASPAC msg.  If a another ASP sends
   a already used label then this ASPAC must be rejected.

2.9.  DRM label parameter

2.9.1.  Description of the problem

   See problem description TID label parameter

2.9.2.  Text changes to the document

   ---------
   Old text: (Section 3.10.15)
   ---------

       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 = 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 integer, which is unique across an AS.

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   ---------
   New text: (Section 3.10.15)
   ---------

       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 = 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 integer, which is unique across an AS. The
      label value has to match the Destination Reference Number between
      the start and the end parameter(Logical AND operation). The rest
      of the DRN between 0 and the begin parameter(if begin parameter
       > 0) AND the end parameter(if end parameter value < 31) and 31 is
      wildcarded.
      An ASP that registers a label will be sent only those DRN-bearing
      messages that match its label.
      An ASP that does not register a label may be sent any DRN-bearing
      message.

2.9.3.  Solution description

   See solution description of the TID label parameter.

2.10.  Usage of the TID and DRN label

2.10.1.  Description of the problem

   The use of the TID and DRM label parameters is unclear.

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2.10.2.  Text changes to the document

   ---------
   Old text: (Section 4.7.2.1)
   ---------

      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
      - ...
      - Start values are the same for each ASP within a RC
      - 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 .

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   ---------
   New text: (Section 4.7.2.1)
   ---------
      After association setup and registration, an ASP normally goes active
      for each AS it registered for.  In the ASPAC message, the ASP can include
      a TID and/or DRN Label Parameter, if applicable for the AS
      in question.

      If at least one of the ASPs within an AS specifies a label, then all the
      ASPs within the AS must specify a unique label in the ASPAC's msg they
      send.

      Each of the ASPs within the AS must specify a unique label at a fixed
      position in the TID or DRN parameter.  The ASP must send the same ASPAC
      to each SG it is attached to, for interworking with the SS7 network.

      The SG builds, per RC, 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
      - ...
      - Start values are the same for each ASP within a RC
      - End values are the same for each ASP within a RC
      - TID and/or 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."

   ---------
   Old text: (Section 4.7.3.1)
   ---------

      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.

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   ---------
   New text: (Section 4.7.3.1)
   ---------

      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
      if the result of the AND operation exactly matches the "Label" field,
      then the message is sent to the ASP that registered for this label via the
      ASPAC msg.

      An ASP that registers a label will be sent only those TID-bearing
      messages that match its label.

      An ASP that does not register a label may be sent any TID-bearing
      message.

      If an ASP is not available, the SG may generate (X)UDTS "routing
      failure", if the return option is used.

2.10.3.  Solution description

   Improving the clarity of the use of the TID and DRM label parameters:

   If the result of the AND operation exactly matches the "Label" field,
   then the message is sent to the ASP that registered for this label
   via the ASPAC msg.

   An ASP that registers a label will be sent only those TID-bearing
   messages that match its label.  An ASP that does not register a label
   may be sent any TID-bearing message.

   Redundancy - The label values are fixed length (16 bits).  So why do
   we need both a "Start" and an "End" position for applying the mask?
   One or the other would seem to be enough.

   Simplicity - Why bother with a partial-sized mask at a specified
   "start" bit.  Why not just specify a "full-sized" 32-bit (TID) or 23-
   bit (DRM) mask?  Then we do not need a "start" and "end" position.

   Contradictions - Section 4.7.2.1 states that "All the ASPs within the
   AS _must_ specify a unique label at a fixed position in the TID or
   DRN parameter."  The "must" here contradicts that fact the the TID
   and DRM parameters are listed as Optional in the ASPAC msg.  Thus if

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   a label is present, then all ASP's belonging to that AS, must
   specifiy a label in the ASPAC msg.

2.11.   Address Range paramete

2.11.1.  Description of the problem

   It should explicitly state the order of the minimum and maximum
   addresses in this parameter.  The most logical order would probably
   be first the min, followed by the max.

2.11.2.  Text changes to the document

   ---------
   Old text: (Section 3.10.17)
   ---------

    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.

   ---------
   New text: (Section 3.10.17)
   ---------

    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. The minimum address must be first and the maximun

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                 address must follow the minimum.

2.11.3.  Solution description

   State the order of the minimum and maximum addresses in this
   parameter.  The logical order is first the min, followed by the max.

2.12.  Interpretation of the mask parameter

2.12.1.  Description of the problem

   The mask paramater in the DAUD, DAVA and DUNA SUA messages can be in
   the range from 0 to 255 bits.  This can go over the maximun pointcode
   range of 24 bits.  Also if a ASP request via DAUD with a mask
   parameter of 24, the SG would need to return all pointcodes it know
   in his network to the ASP.  (Which could be a lot).

2.12.2.  Text changes to the document

   ---------
   Old text: (Section 3.9.18)
   ---------

   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.

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   ---------
   New text: (Section 3.9.18)
   ---------

   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".

      The range of mask parameter is limited to 0-24 for ANSI networks and
      is NOT used for ITU networks.

2.12.3.  Solution description

   The parameter is limited to 14 bits for ANSI networks and is NOT USED
   in ITU networks.

2.13.  Reply on errors contained in a error message

2.13.1.  Description of the problem

   If a error message arrives with a error in it, what should be send
   out?  Nothing in the RFC3868 describes this possibility.

2.13.2.  Text changes to the document

   ---------
   Old text: (Section 3.7.1)
   ---------

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   ---------
   New text: (Section 3.7.1)
   ---------

   Error messages MUST NOT be generated in response to other Error messages.

2.13.3.  Solution description

   No error msg must be send back in response on a received error
   message(containing a error).  This would otherwise possibly lead to a
   storm of exchange error messages.

2.14.  Use of stream 0 for SSNM messages

2.14.1.  Description of the problem

   There seems to be some confusion in paragraph 4.5.1.  First it is
   mentioned NOT to use stream 0 but a few lines later you MUST use
   stream 0 and that happen all in the same context of sending SSNM
   messages(DAUD, DUNA, DAVA..).  It also contradicts statements made in
   paragraph 4.1.1.

2.14.2.  Text changes to the document

   ---------
   Old text: (Section 4.5.1)
   ---------

      DUNA, DAVA, SCON, and DRST messages are sent sequentially and
      processed at the receiver in the order sent.  SCTP stream 0 SHOULD
      NOT be used.  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 unordered.  SCTP stream 0 is used, with optional use of the
      Unordered bit in the SCTP DATA chunk.

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   ---------
   New text: (Section 4.5.1)
   ---------

      DUNA, DAVA, SCON, and DRST messages are sent sequentially and
      processed at the receiver in the order sent. 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 unordered.  SCTP stream 0 is used, with optional use of the
      Unordered bit in the SCTP DATA chunk.

2.14.3.  Solution description

   The SSNM messages should be send on stream 0 of the association.

2.15.  Timer Ta does not exist

2.15.1.  Description of the problem

   Timer Ta is mentioned in paragraph 8 but nowhere specified.

2.15.2.  Text changes to the document

   ---------
   Old text: (Section 8)
   ---------

   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

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   ---------
   New text: (Section 8)
   ---------

   8.  Timer Values

      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

2.15.3.  Solution description

   Timer Ta is removed.

2.16.  Error response on unsupported RKM messages

2.16.1.  Description of the problem

   If RKM messages are not supported by a implementation, a error
   message is send back with error cause "unsupported message Type".  We
   should send back a error message with error cause "unsupported
   message class" .

2.16.2.  Text changes to the document

   ---------
   Old text: (Section 4.4.1)
   ---------
      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".

   ---------
   New text: (Section 4.4.1)
   ---------
      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 Class".

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2.16.3.  Solution description

   Send back a error message with "unsupported message class".  If >RKM
   messages are not supported, the implementation actually rejects a
   whole class of messages, not just a single one.

2.17.  Filler/padding in Global title parameter

2.17.1.  Description of the problem

   The global title digits part of the global title parameter contains
   filler bytes.  They should be called pading bytes so that they are
   not included in the calculation of the length of the global title
   parameter.

2.17.2.  Text changes to the document

   ---------
   Old text: (Section 3.10.2.3)
   ---------
      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.

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   ---------
   New text: (Section 3.10.2.3)
   ---------
      Global Title:

      Octets contain a number of address signals and possibly filler and
      padding 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.|   padding     |
      |                               |if req | sig.  |               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      All filler and padding bits SHOULD be set to 0.

2.17.3.  Solution description

   Insert padding into definition of the global title parameter.

2.18.  Inclusion of routing context in the Routing key parameter

2.18.1.  Description of the problem

   The Routing conext is missing from the Routing key parameter of the
   REG message, so leading to a inconsistency with section 4.4.1 where
   it is mentioned that the RC has to be present in order to change the
   registration data of a certain RC.  If the RC is not present, then
   the registration data can not be identified and changed.

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2.18.2.  Text changes to the document

   ---------
   Old text: (Section 3.10.14)
   ---------
      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

   ---------
   New text: (Section 3.10.14)
   ---------
      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
            Routing Context            Optional *2

      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.

      Note 2:    The Routing Context parameter is included in the Routing
                 Key when the ASP wishes to alter an existing Routing Key
                 which corresponds to the indicated Routing Context.  The
                 Routing Context parameter MUST only occur once in the Key
                 parameters.

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2.18.3.  Solution description

   Include the routing context parameter in the routing key parameter.
   And keep the text of section 4.4.1.

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3.  Security considerations

   No new treats have been identified besides the already known in SUA
   [RFC3868] [1].

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4.  Acknowledgments

   The authors wish to thank B. Nagelberg, B. Bidulock, T. Asveren, S.
   Karl, K. Morneault and many others for their invaluable comments.

5.  References

   [1]  Loughney, J., Sidebottom, G., Verwimp, G., Coene, L., Keller,
        J., and B. Bidulock, "Signalling Connection Control Part User
        Adaptation Layer (SUA)", RFC 3868, October 2004.

   [2]  Malkin, G., "Internet Users' Glossary", RFC 1983, August 1996.

   [3]  Mockapetris, P., "Domain names - Implementation and
        Specification", RFC 1035, November 1987.

   [4]  ITU, "Q.714 : SCCP procedures", Q. 714, July 1997.

   [5]  ANSI, "T1.112.4 : SCCP procedures", T. 1.112.4, December 1993.

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Appendix A.  Changes Control

A.1.  Changes from v00 to v01

   - Change of boilerplate

   - Typos.

   - Paragraph 2.6 ASP routing context: replacement text for section
   1.5.2

   - Paragraph 2.10 Usage of TID and DRM label parameter: text
   clarification for solution description

   - Paragraph 2.8 Use of ANSI intermediate signaling network
   identification (ISNI) parameter: Removed, no text proposed.

A.2.  Changes from v01 to v02

   - Typos.

   - Paragraph 2.17 Filler/padding in Global title parameter: new

   - Paragraph 2.18 Inclusion of routing context in the Routing key
   parameter: new

   - Paragraph 2.8 TID label parameter:Changed: Another attempt at
   clarifying what a SG could be doing with TID label.

   - Paragraph 2.9 DRM label parameter:Changed: Another attempt at
   clarifying what a SG could be doing with DRM label.

   - Paragraph 2.10 Usage of TID and DRM label parameter:Changed:
   Another attempt at clarifying what a SG could be doing with TID and
   DRM labels.

   -

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Authors' Addresses

   Lode Coene
   Siemens
   Atealaan 32
   Herentals  2200
   Belgium

   Phone: +32-14-252081
   Email: lode.coene@siemens.com

   John Loughney
   Nokia
   Itdmerenkatu 11-13
   Espoo  00180
   Finland

   Phone: +358 50 483 6242
   Email: john.loughney@nokia.com

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