rfc3525.txt

OTP是开放电信平台的简称

Network Working Group                                          C. Groves
Request for Comments: 3525                                   M. Pantaleo
Obsoletes: 3015                                              LM Ericsson
Category: Standards Track                                    T. Anderson
                                                              Consultant
                                                               T. Taylor
                                                         Nortel Networks
                                                                 Editors
                                                               June 2003


                  Gateway Control Protocol Version 1

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

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

Abstract

   This document defines the protocol used between elements of a
   physically decomposed multimedia gateway, i.e., a Media Gateway and a
   Media Gateway Controller.  The protocol presented in this document
   meets the requirements for a media gateway control protocol as
   presented in RFC 2805.

   This document replaces RFC 3015.  It is the result of continued
   cooperation between the IETF Megaco Working Group and ITU-T Study
   Group 16.  It incorporates the original text of RFC 3015, modified by
   corrections and clarifications discussed on the Megaco
   E-mail list and incorporated into the Study Group 16 Implementor's
   Guide for Recommendation H.248.  The present version of this document
   underwent  ITU-T Last Call as Recommendation H.248 Amendment 1.
   Because of ITU-T renumbering, it was published by the ITU-T as
   Recommendation H.248.1 (03/2002), Gateway Control Protocol Version 1.

   Users of this specification are advised to consult the H.248 Sub-
   series Implementors' Guide at http://www.itu.int/itudoc/itu-
   t/com16/implgd for additional corrections and clarifications.





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RFC 3525                Gateway Control Protocol               June 2003


Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

Table of Contents

   1 Scope.........................................................5
     1.1 Changes From RFC 3015.....................................5
     1.2 Differences From ITU-T Recommendation H.248.1 (03/2002)...5
   2 References....................................................6
     2.1 Normative references......................................6
     2.2 Informative references....................................9
   3 Definitions..................................................10
   4 Abbreviations................................................11
   5 Conventions..................................................12
   6 Connection model.............................................13
     6.1 Contexts.................................................16
     6.2 Terminations.............................................17
       6.2.1 Termination dynamics.................................21
       6.2.2 TerminationIDs.......................................21
       6.2.3 Packages.............................................22
       6.2.4 Termination properties and descriptors...............23
       6.2.5 Root Termination.....................................25
   7 Commands.....................................................26
     7.1 Descriptors..............................................27
       7.1.1 Specifying parameters................................27
       7.1.2 Modem descriptor.....................................28
       7.1.3 Multiplex descriptor.................................28
       7.1.4 Media descriptor.....................................29
       7.1.5 TerminationState descriptor..........................29
       7.1.6 Stream descriptor....................................30
       7.1.7 LocalControl descriptor..............................31
       7.1.8 Local and Remote descriptors.........................32
       7.1.9 Events descriptor....................................35
       7.1.10 EventBuffer descriptor..............................38
       7.1.11 Signals descriptor..................................38
       7.1.12 Audit descriptor....................................40
       7.1.13 ServiceChange descriptor............................41
       7.1.14 DigitMap descriptor.................................41
       7.1.15 Statistics descriptor...............................46
       7.1.16 Packages descriptor.................................47
       7.1.17 ObservedEvents descriptor...........................47
       7.1.18 Topology descriptor.................................47
       7.1.19 Error Descriptor....................................50
     7.2 Command Application Programming Interface................50
       7.2.1 Add..................................................51



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       7.2.2 Modify...............................................52
       7.2.3 Subtract.............................................53
       7.2.4 Move.................................................55
       7.2.5 AuditValue...........................................56
       7.2.6 AuditCapabilities....................................59
       7.2.7 Notify...............................................60
       7.2.8 ServiceChange........................................61
       7.2.9 Manipulating and Auditing Context Attributes.........65
       7.2.10 Generic Command Syntax..............................66
     7.3 Command Error Codes......................................66
   8 Transactions.................................................66
     8.1 Common parameters........................................68
       8.1.1 Transaction Identifiers..............................68
       8.1.2 Context Identifiers..................................68
     8.2 Transaction Application Programming Interface............69
       8.2.1 TransactionRequest...................................69
       8.2.2 TransactionReply.....................................69
       8.2.3 TransactionPending...................................71
     8.3 Messages.................................................72
   9 Transport....................................................72
     9.1 Ordering of Commands.....................................73
     9.2 Protection against Restart Avalanche.....................74
   10 Security Considerations.....................................75
     10.1 Protection of Protocol Connections......................75
     10.2 Interim AH scheme.......................................76
     10.3 Protection of Media Connections.........................77
   11 MG-MGC Control Interface....................................78
     11.1 Multiple Virtual MGs....................................78
     11.2 Cold start..............................................79
     11.3 Negotiation of protocol version.........................79
     11.4 Failure of a MG.........................................80
     11.5 Failure of an MGC.......................................81
   12 Package definition..........................................82
     12.1 Guidelines for defining packages........................82
       12.1.1 Package.............................................83
       12.1.2 Properties..........................................84
       12.1.3 Events..............................................85
       12.1.4 Signals.............................................85
       12.1.5 Statistics..........................................86
       12.1.6 Procedures..........................................86
     12.2 Guidelines to defining Parameters to Events and Signals.86
     12.3 Lists...................................................87
     12.4 Identifiers.............................................87
     12.5 Package registration....................................88
   13 IANA Considerations.........................................88
     13.1 Packages................................................88
     13.2 Error codes.............................................89
     13.3 ServiceChange reasons...................................89



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   ANNEX A  Binary encoding of the protocol.......................90
     A.1 Coding of wildcards......................................90
     A.2 ASN.1 syntax specification...............................92
     A.3 Digit maps and path names...............................111
   ANNEX B Text encoding of the protocol.........................113
     B.1 Coding of wildcards.....................................113
     B.2 ABNF specification......................................113
     B.3 Hexadecimal octet coding................................127
     B.4 Hexadecimal octet sequence..............................127
   ANNEX C Tags for media stream properties......................128
     C.1 General media attributes................................128
     C.2 Mux properties..........................................130
     C.3 General bearer properties...............................130
     C.4 General ATM properties..................................130
     C.5 Frame Relay.............................................134
     C.6 IP......................................................134
     C.7 ATM AAL2................................................134
     C.8 ATM AAL1................................................136
     C.9 Bearer capabilities.....................................137
     C.10 AAL5 properties........................................147
     C.11 SDP equivalents........................................148
     C.12 H.245..................................................149
   ANNEX D Transport over IP.....................................150
     D.1 Transport over IP/UDP using Application Level Framing ..150
       D.1.1 Providing At-Most-Once functionality................150
       D.1.2 Transaction identifiers and three-way handshake.....151
       D.1.3 Computing retransmission timers.....................152
       D.1.4 Provisional responses...............................153
       D.1.5 Repeating Requests, Responses and Acknowledgements..153
     D.2 Using TCP...............................................155
       D.2.1 Providing the At-Most-Once functionality............155
       D.2.2 Transaction identifiers and three-way handshake.....155
       D.2.3 Computing retransmission timers.....................156
       D.2.4 Provisional responses...............................156
       D.2.5 Ordering of commands................................156
   ANNEX E  Basic packages.......................................157
     E.1 Generic.................................................157
     E.2 Base Root Package.......................................159
     E.3 Tone Generator Package..................................161
     E.4 Tone Detection Package..................................163
     E.5 Basic DTMF Generator Package............................166
     E.6 DTMF detection Package..................................167
     E.7 Call Progress Tones Generator Package...................169
     E.8 Call Progress Tones Detection Package...................171
     E.9 Analog Line Supervision Package.........................172
     E.10 Basic Continuity Package...............................175
     E.11 Network Package........................................178
     E.12 RTP Package............................................180



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     E.13 TDM Circuit Package....................................182
   APPENDIX I EXAMPLE CALL FLOWS (INFORMATIVE)...................184
     A.1 Residential Gateway to Residential Gateway Call.........184
       A.1.1 Programming Residential GW Analog Line Terminations
             for Idle Behavior...................................184
       A.1.2 Collecting Originator Digits and Initiating
             Termination.........................................186
   APPENDIX II  Changes From RFC 3015............................195
   Intellectual Property Rights..................................210
   Acknowledgments...............................................211
   Authors' Addresses............................................212
   Full Copyright Statement......................................213

1  Scope

   The present document, which is identical to the published version of
   ITU-T Recommendation H.248.1 (03/2002) except as noted below, defines
   the protocols used between elements of a physically decomposed
   multimedia gateway.  There are no functional differences from a
   system view between a decomposed gateway, with distributed sub-
   components potentially on more than one physical device, and a
   monolithic gateway such as described in ITU-T Recommendation H.246.
   This document does not define how gateways, multipoint control units
   or interactive voice response units (IVRs) work.  Instead it creates
   a general framework that is suitable for these applications.

   Packet network interfaces may include IP, ATM or possibly others.
   The interfaces will support a variety of Switched Circuit Network
   (SCN) signalling systems, including tone signalling, ISDN, ISUP, QSIG
   and GSM.  National variants of these signalling systems will be
   supported where applicable.

1.1 Changes From RFC 3015

   The differences between this document and RFC 3015 are documented in
   Appendix II.

1.2 Differences From ITU-T Recommendation H.248.1 (03/2002)

   This document differs from the corresponding ITU-T publication in the
   following respects:

   -  Added IETF front matter in place of the corresponding ITU-T
      material.

   -  The ITU-T summary is too H.323-specific and has been omitted.





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   -  The IETF conventions have been stated as governing this document.
      As discussed in section 5 below, this gives slightly greater
      strength to "should" requirements.

   -  The Scope section (just above) has been edited slightly to suit
      its IETF context.

   -  Added normative references to RFCs 2026 and 2119.

   -  Figures 4, 5, and 6 show the centre of the context for greater
      clarity.  Also added Figure 6a showing an important additional
      example.

   -  Added a paragraph in section 7.1.18 which was approved in the
      Implementor's Guide but lost inadvertently in the ITU-T approved
      version.

   -  This document incorporates corrections to the informative examples
      in Appendix I which also appear in H.248.1 version 2, but which
      were not picked up in H.248.1 (03/2002).