A Telephony Gateway REgistration Protocol (TGREP)
RFC 5140

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Network Working Group                                       M. Bangalore
Request for Comments: 5140                                      R. Kumar
Category: Standards Track                                   J. Rosenberg
                                                                   Cisco
                                                               H. Salama
                                                          Citex Software
                                                               D.N. Shah
                                                             Moowee Inc.
                                                              March 2008

           A Telephony Gateway REgistration Protocol (TGREP)

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.

Abstract

   This document describes the Telephony Gateway Registration Protocol
   (TGREP) for registration of telephony prefixes supported by telephony
   gateways and soft switches.  The registration mechanism can also be
   used to export resource information.  The prefix and resource
   information can then be passed on to a Telephony Routing over IP
   (TRIP) Location Server, which in turn can propagate that routing
   information within and between Internet Telephony Administrative
   Domains (ITADs).  TGREP shares a lot of similarities with the TRIP
   protocol.  It has similar procedures and finite state machine for
   session establishment.  It also shares the same format for messages
   and a subset of attributes with TRIP.

Bangalore, et al.           Standards Track                     [Page 1]
RFC 5140                         TGREP                        March 2008

Table of Contents

   1. Introduction ....................................................3
   2. Terminology and Definitions .....................................5
   3. TGREP: Overview of Operation ....................................6
   4. TGREP Attributes ................................................7
      4.1. TotalCircuitCapacity Attribute .............................8
      4.2. AvailableCircuits Attribute ................................9
      4.3. CallSuccess Attribute .....................................10
      4.4. Prefix Attributes .........................................12
      4.5. TrunkGroup Attribute ......................................13
      4.6. Carrier Attribute .........................................15
   5. TrunkGroup and Carrier Address Families ........................16
      5.1. Address Family Syntax .....................................17
   6. Gateway Operation ..............................................18
      6.1. Session Establishment .....................................18
      6.2. UPDATE Messages ...........................................19
      6.3. KEEPALIVE Messages ........................................19
      6.4. Error Handling and NOTIFICATION Messages ..................19
      6.5. TGREP Finite State Machine ................................19
      6.6. Call Routing Databases ....................................19
      6.7. Multiple Address Families .................................20
      6.8. Route Selection and Aggregation ...........................20
   7. LS/Proxy Behavior ..............................................20
      7.1. Route Consolidation .......................................22
      7.2. Aggregation ...............................................23
      7.3. Consolidation versus Aggregation ..........................23
   8. Security Considerations ........................................23
   9. IANA Considerations ............................................24
      9.1. Attribute Codes ...........................................24
      9.2. Address Family Codes ......................................24
   10. Acknowledgments ...............................................25
   11. References ....................................................25
      11.1. Normative References .....................................25
      11.2. Informative References ...................................26

Bangalore, et al.           Standards Track                     [Page 2]
RFC 5140                         TGREP                        March 2008

1.  Introduction

   It is assumed that the reader of this document is familiar with TRIP
   [2, 12].  In typical Voice over IP (VoIP) networks, Internet
   Telephony Administrative Domains (ITADs) will deploy numerous
   gateways for the purposes of geographical diversity, capacity, and
   redundancy.  When a call arrives at the domain, it must be routed to
   one of those gateways.  Frequently, an ITAD will break its network