A Taxonomy of Session Initiation Protocol (SIP) Back-to-Back User Agents
draft-ietf-straw-b2bua-taxonomy-02

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STRAW Working Group                                            H. Kaplan
Internet-Draft                                                V. Pascual
Intended status: Informational                               Acme Packet
Expires: November 11, 2013                                  May 10, 2013

A Taxonomy of Session Initiation Protocol (SIP) Back-to-Back User Agents
                   draft-ietf-straw-b2bua-taxonomy-02

Abstract

   In many SIP deployments, SIP entities exist in the SIP signaling path
   between the originating UAC and final terminating UAS, which go
   beyond the definition of a Proxy, performing functions not defined in
   standards-track RFCs.  The only term for such devices provided in
   [RFC3261] is for a Back-to-Back User Agent (B2BUA), which is defined
   as the logical concatenation of a User Agent Server (UAS) and User
   Agent Client (UAC).

   There are numerous types of SIP Back-to-Back User Agents (B2BUAs),
   performing different roles in different ways.  For Example IP-PBXs,
   SBCs and Application Servers.  This document identifies several
   common B2BUA roles, in order to provide taxonomy other documents can
   use and reference.

Status of This Memo

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   This Internet-Draft will expire on November 11, 2013.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Kaplan & Pascual       Expires November 11, 2013                [Page 1]
Internet-Draft             Taxonomy of B2BUAs                   May 2013

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Table of Contents

   1.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  B2BUA Role Types  . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Signaling-plane B2BUA Roles . . . . . . . . . . . . . . .   3
       3.1.1.  Proxy-B2BUA . . . . . . . . . . . . . . . . . . . . .   3
       3.1.2.  Signaling-only  . . . . . . . . . . . . . . . . . . .   4
       3.1.3.  SDP-Modifying Signaling-only  . . . . . . . . . . . .   4
     3.2.  Media-plane B2BUA Roles . . . . . . . . . . . . . . . . .   4
       3.2.1.  Media-relay . . . . . . . . . . . . . . . . . . . . .   5
       3.2.2.  Media-aware . . . . . . . . . . . . . . . . . . . . .   5
       3.2.3.  Media-termination . . . . . . . . . . . . . . . . . .   5
   4.  Mapping SIP Device Types to B2BUA Roles . . . . . . . . . . .   6
     4.1.  SIP PBXs and Softswitches . . . . . . . . . . . . . . . .   6
     4.2.  Application Servers . . . . . . . . . . . . . . . . . . .   6
     4.3.  Session Border Controllers  . . . . . . . . . . . . . . .   6
     4.4.  Transcoders . . . . . . . . . . . . . . . . . . . . . . .   6
     4.5.  Conference Servers  . . . . . . . . . . . . . . . . . . .   7
     4.6.  P-CSCF and IBCF Functions . . . . . . . . . . . . . . . .   7
     4.7.  S-CSCF Function . . . . . . . . . . . . . . . . . . . . .   7
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   8
   8.  Informative References  . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Terminology

   B2BUA: a SIP Back-to-Back User Agent, which is the logical
   combination of a User Agent Server (UAS) and User Agent Client (UAC).

   UAS: a SIP User Agent Server.

   UAC: a SIP User Agent Client.

2.  Introduction

Kaplan & Pascual       Expires November 11, 2013                [Page 2]
Internet-Draft             Taxonomy of B2BUAs                   May 2013

   In current SIP deployments, there are numerous forms of B2BUAs,
   operating at various layers of the protocol stack, and for various
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