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Network Working Group Brian Bidulock
INTERNET-DRAFT OpenSS7 Corporation
Expires in six months January 2, 2003
Multiple Signalling Gateway Support
for
Signalling User Adaptation Layers
<draft-bidulock-sigtran-multisg-01.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with
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Abstract
This Internet-Draft describes Load Selection for Signalling User
Adaptation Protocols [M3UA...TUA01], which permits an Application
Server Processes (ASP) to indicate its placement within an Application
Server and permits an Signalling Gateway (SG) to distribute traffic
over ASPs in Application Servers under Application Server Process
(ASP) control.
1. Introduction
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1.1. Scope
This Internet-Draft provides parameters and procedures in extension
to the parameters and procedures of the Signalling User Adaptation
Layers (UAs) [M3UA...TUA01], for the purpose of supporting Application
Servers interworking with multiple Signalling Gateways to the SS7
Network.
UA implementations with Multiple SG Support are intended to be
compatible with UA implementations not supporting this configuration.
MULTI-SG is only applicable to Signalling Gateway (SG)-Application
Server Process (ASP) configurations in which ASP are supporting
Application Server (AS) connectivity to an SS7 network via multiple
SGs.[1] MULTI-SG is not applicable to configurations of IPSPs working
in a point-to-point network without relay points.[2]
1.2. Terminology
Multiple SG Support (MULTI-SG) supplements the terminology used in
the UA documents [M3UA...TUA01] by adding the following terms:
Multiple SG Support (MULTI-SG) - the parameters and procedures
provided in this document.
Signalling User Adaptation Layer (UA) - one or more of the Stream
Control Transmission Protocol (SCTP) [RFC 2960] SS7 Signalling User
Adaptation Layers [M3UA...TUA01] supporting the concept of a
Routing Context.
1.3. Overview
MULTI-SG provides procedures in addition to the UA procedures[3]
that provides for seamless interworking of SS7 Network Management with
Application Server Processes (ASPs) supporting Application Servers
(AS) to multiple Signalling Gateways (SGs). MULTI-SG procedures
provide support for the following functions not provided for in the
existing UA documents:
+ Support for fail-over of SCTP associations between Signalling
Gateways (SGs).
+ Support for rerouting of traffic destined to Signalling Endpoints
(SEP) in SS7 Network between Signalling Gateways (SGs).
+ Support for seamless interworking with SS7 Changeback [Q.704]
procedures towards the SS7 Network for rerouting of traffic between
SGs for elminating message mis-sequencing across the interworking
point between the SS7 and IP networks.
MUTLI-SG supplements the procedures for the diversion of traffic
during fail-over or restoration of ASPs, SGPs and IPSPs already
provided for in "Correlation Id and Heartbeat Procedures (CORID)
Supporting Lossless Fail-Over between SCTP Associations" [CORID]. The
benefits of MULTI-SG can, nevertheless, be supported indepedent from
CORID [CORID]
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Internet Draft UA MULTI-SG January 2, 2003
1.3.1. Multiple SGs
No procedures are described which provide for reduction of message
loss, duplication or mis-sequencing in multiple SG configurations in
the existing UA procedures.
1.3.1.1. Fail-over of routesets between SGs
1.3.1.2. Redirection of routesets between SGs
1.4. Sample Configurations
|
SS7 IP
Network | Network
_______________ _______ ____
| | _______| ______| | / \
| | |_______| ____| ASP | | |
B/D-Links | | | SGP |________ | |_______| | |
___________| STP SG|_______| | | _______ | |
/| | | |__ + | | __| | | AS |
/ | | SGP |__ + | | __| ASP | | |
\ / | | |_______| + | | |_______| | |
\ / |_______________| | | _______ | |
\ / C- | + | | __| | \____/
X Links| | + | | __| ASP | ____
/ \ _|_____________ + | | |_______| / \
/ \ | | _______| | | _______ | |
/ \ | | |__ + | | __| | | |
\ | | | SGP |__ + | | __| ASP | | |
__________\| STP SG|_______| + | | |_______| | AS |
| | | |________|_| _______ | |
| | SGP |_______ |_____| | | |
| | |_______| |______| ASP | | |
|_______________| SCTP |_______| \___ /
| Associations
|
Figure 1. Example (A) Sample Multiple-SG Configuration
A typical Example (A) configuration multiple Signalling Gateways is
illustrated in Figure 1. In this configuration a number of
Application Server Processes (ASPs) serving a number of Application
Servers (ASs) are connected to two Signalling Gateways (SGs). The SGs
appear as mated SS7 Signalling Transfer Points (STPs) [Q.705] to the
SS7 Network. Traffic originating at Signalling Endpoints (SEP) in the
SS7 network and directed toward SEP in the IP network (i.e.,
Application Servers) is loadshared over the STPs by the Signalling
Link Selection (SLS) [Q.704] value associated with each message.
Traffic originating at the SEP in the IP network (i.e, AS) is
loadshared over the SGs in the same fashion.
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Internet Draft UA MULTI-SG January 2, 2003
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 [RFC
2119].
3. Protocol Elements
3.1. Parameters
3.2. Messages
4. Procedures
4.1. AS and ASP State Maintenance
4.1.1. ASP State
4.1.2. AS State
4.1.3. ASP Up Procedures
4.1.4. ASP Down Procedures
4.1.5. ASP Active Procedures
4.1.6. ASP Inactive Procedures
4.1.7. Notify Procedures
5. Examples
6. Security
Load Selection does not introduce any new security risks or
considerations that are not already inherent in the UA [M3UA...TUA01]
Please see the "Security" sections of M3UA, SUA and TUA [M3UA...TUA01]
for security considerations and recommendations that are applicable to
each of these UAs.
7. IANA Considerations
Acknowledgments
The authors would like to thank for their valuable comments and
suggestions.
Notes
[1] This is commonly referred to within the SIGTRAN WG as the
"backhaul" case.
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Internet Draft UA MULTI-SG January 2, 2003
[2] This is commonly referred to within the SIGTRAN WG as the "peer-
to-peer" case.
[3] See Section 4 of M3UA, SUA and TUA [M3UA...TUA01].
References
M3UA.
G. Sidebottom, J. Pastor-Balbas, I. Rytina, G. Mousseau, L. Ong,
H. J. Schwarzbauer, K. Gradischnig, K. Morneault, M. Kalla, N.
Glaude, B. Bidulock and J. Loughney, "SS7 MTP3-User Adaptation
Layer (M3UA)," <draft-ietf-sigtran-m3ua-10.txt>, Internet
Engineering Task Force - Signalling Transport Working Group
(November, 2001). Work In Progress.
SUA09.
J. Loughney, G. Sidebottom, G. Mousseau, S. Lorusso, L. Coene, G.
Verwimp, J. Keller, F. E. Gonzalez, W. Sully, S. Furniss and B.
Bidulock, "SS7 SCCP-User Adaptation Layer (SUA)," <draft-ietf-
sigtran-sua-09.txt>, Internet Engineering Task Force - Signalling
Transport Working Group (June 2001). Work In Progress.
TUA01.
B. Bidulock, "SS7 TCAP-User Adaptation Layer (TUA)," <draft-
bidulock-sigtran-tua-01.txt>, Internet Engineering Task Force -
Signalling Transport Working Group (January 2, 2003). Work In
Progress.
RFC 2960.
R. Stewart, Q. Xie, K. Morneault, C. Sharp, H. J. Schwarzbauer,
T. Taylor, I. Rytina, H. Kalla, L. Zhang and V. Paxson, "Stream
Control Transmission Protocol (SCTP)," RFC 2960, The Internet
Society (February 2000).
Q.704.
ITU, "Message Transfer Part - Signalling Network Functions and
Messages," ITU-T Recommendation Q.704, ITU-T Telecommunication
Standardization Sector of ITU, Geneva (March 1993). (Previously
"CCITT Recommendation")
CORID.
B. Bidulock, "Correlation Id and Heartbeat Procedures Supporting
Lossless Fail-Over," <draft-bidulock-sigtran-corid-01.txt>,
Internet Engineering Task Force - Signalling Transport Working
Group (January 2, 2003). Work In Progress.
Q.705.
ITU, "Signalling System No. 7 - Signalling Network Structure,"
ITU-T Recommendation Q.705, ITU-T Telecommunication
Standardization Sector of ITU, Geneva (March 1993). (Previously
"CCITT Recommendation")
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Internet Draft UA MULTI-SG January 2, 2003
RFC 2119.
S. Bradner, "Key words for use in RFCs to Indicate Requirement
Levels," RFC 2119 - BCP 14, The Internet Society (March 1997).
Author's Addresses
Brian Bidulock Phone: +1-780-490-1141
OpenSS7 Corporation Email: bidulock@openss7.org
1469 Jeffreys Crescent URL: http//www.openss7.org/
Edmonton, AB T6L 6T1
Canada
This Internet draft expires July, 2003.
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List of Illustrations
Figure 1 Example (A) Sample Multiple-SG Configuration ......... 3
Table of Contents
Status of this Memo ........................................... 1
Abstract ...................................................... 1
1 Introduction ................................................ 1
1.1 Scope ..................................................... 2
1.2 Terminology ............................................... 2
1.3 Overview .................................................. 2
1.3.1 Multiple SGs ............................................ 3
1.4 Sample Configurations ..................................... 3
2 Conventions ................................................. 4
3 Protocol Elements ........................................... 4
3.1 Parameters ................................................ 4
3.2 Messages .................................................. 4
4 Procedures .................................................. 4
4.1 AS and ASP State Maintenance .............................. 4
4.1.1 ASP State ............................................... 4
4.1.2 AS State ................................................ 4
4.1.3 ASP Up Procedures ....................................... 4
4.1.4 ASP Down Procedures ..................................... 4
4.1.5 ASP Active Procedures ................................... 4
4.1.6 ASP Inactive Procedures ................................. 4
4.1.7 Notify Procedures ....................................... 4
5 Examples .................................................... 4
6 Security .................................................... 4
7 IANA Considerations ......................................... 4
Acknowledgments ............................................... 4
Notes ......................................................... 4
References .................................................... 5
Author's Addresses ............................................ 6
List of Illustrations ......................................... 7
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Internet Draft UA MULTI-SG January 2, 2003
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