draft-bidulock-sigtran-multisg-01

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
  all provisions of Section 10 or RFC 2026.  Internet-Drafts are working
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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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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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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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  [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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  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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