draft-bidulock-sigtran-multisg-02

Network Working Group                                     Brian Bidulock
INTERNET-DRAFT                                       OpenSS7 Corporation

                                                           July 26, 2003
Expires in January 2004

                  Multiple Signalling Gateway Support
                                  for
                   Signalling User Adaptation Layers
                <draft-bidulock-sigtran-multisg-02.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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Copyright

     Copyright (C) The Internet Society (2003).  All Rights Reserved.

Abstract

     This Internet-Draft describes Load Selection for Signalling User
  Adaptation Protocols [M3UA, SUA..TUA], 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.

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Contents

     A complete table of contents, list of tables and illustrations, and
  change history appears at the end of this document.

1.  Introduction

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, SUA..TUA], 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, SUA..TUA] 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, SUA..TUA] 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.

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     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]

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

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  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.

Notes for Section 1

  [1]  This is commonly referred to within the SIGTRAN WG as the
       "backhaul" case.

  [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, SUA..TUA].

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,

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  SUA..TUA] Please see the SIGTRAN Security document [SIGSEC] for
  security considerations and recommendations that are applicable to
  each of these UAs.

7.  IANA Considerations

0.  Change History

  This section will be deleted once this memo is finalized.

0.2.  Changes from Version 0.1 to Version 0.2

0.1.  Changes from Version 0.0 to Version 0.1

R.  References

R.1.  Normative References

  [M3UA]  Sidebottom, G., Morneault, K. and Pastor-Balbas, J., (eds),
       "Signaling System 7 (SS7) Message Transfer Part 3 (MTP3) - User
       Adaptation Layer (M3UA)," RFC 3332, Internet Engineering Task
       Force - Signalling Transport Working Group (September, 2002).

  [RFC 2960]  Stewart, R., Xie, Q., Morneault, K., Sharp, C.,
       Schwarzbauer, H. J., Taylor, T., Rytina, I., Kalla, H., Zhang, L.
       and Paxson, V., "Stream Control Transmission Protocol (SCTP),"
       RFC 2960, The Internet Society (February 2000).

  [RFC 2119]  Bradner, S., "Key words for use in RFCs to Indicate
       Requirement Levels," RFC 2119 - BCP 14, The Internet Society
       (March 1997).

  [SIGSEC]  Loughney, J., Tuexen, M. and Pastor-Balbas, J., "Security
       Considerations for SIGTRAN Protocols," <draft-ietf-sigtran-
       security-03.txt>, Internet Engineering Task Force - Signalling
       Transport Working Group (June 29, 2003).  Work In Progress.

R.2.  Informative References

  [SUA]  Loughney, J., Sidebottom, G., Coene, L., Verwimp, G., Keller,
       J. and Bidulock, B., "SS7 SCCP-User Adaptation Layer (SUA),"
       draft-ietf-sigtran-sua-15.txt, Internet Engineering Task Force -
       Signalling Transport Working Group (June 30, 2003).  Work In
       Progress.

  [ISUA]  Bidulock, B., "SS7 ISUP-User Adaptation Layer (ISUA)," <draft-
       bidulock-sigtran-isua-01.txt>, Internet Engineering Task Force -
       Signalling Transport Working Group (July 26, 2003).  Work In
       Progress.

  [TUA]  Bidulock, B., "SS7 TCAP-User Adaptation Layer (TUA)," <draft-
       bidulock-sigtran-tua-02.txt>, Internet Engineering Task Force -

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       Signalling Transport Working Group (July 26, 2003).  Work In
       Progress.

  [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]  Bidulock, B., "Correlation Id and Heartbeat Procedures
       Supporting Lossless Fail-Over," <draft-bidulock-sigtran-
       corid-02.txt>, Internet Engineering Task Force - Signalling
       Transport Working Group (July 26, 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")

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 draft expires January 2004.

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                        List of Illustrations

  Figure 1. Example (A) Sample Multiple-SG Configuration ..........    3

                          Table of Contents

  Status of this Memo .............................................    1
  Copyright .......................................................    1
  Abstract ........................................................    1
  Contents ........................................................    2
  1 Introduction ..................................................    2
  1.1 Scope .......................................................    2
  1.2 Terminology .................................................    2
  1.3 Overview ....................................................    2
  1.3.1 Multiple SGs ..............................................    3
  1.4 Sample Configurations .......................................    3
  Notes for Section 1 .............................................    4
  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 ...........................................    5
  0 Change History ................................................    5
  0.2 Changes from Version 0.1 to Version 0.2 .....................    5
  0.1 Changes from Version 0.0 to Version 0.1 .....................    5
  R References ....................................................    5
  R.1 Normative References ........................................    5
  R.2 Informative References ......................................    5
  Author's Addresses ..............................................    6
  List of Illustrations ...........................................    7
  Table of Contents ...............................................    7

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