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TS 29.079 (CT3)
OMR – Optimal Media Routeing within the IMS – Stage 3

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V14.0.0 (PDF)    2017/03    92 p.
V13.0.0    2015/12    92 p.
V12.3.0    2015/06    92 p.
V11.7.0    2015/06    92 p.
V10.8.0    2015/06    78 p.

Rapporteur:  Mr. Brinkmann, Horst
See also:  –

This document defines optional Optimal Media Routeing (OMR) procedures that can be applied by entities in the IMS that control media resources and are capable of manipulating the Session Description Protocol (SDP) as defined by RFC 4566.

The OMR procedures in the present specification relate to the handling of OMR-specific SDP attributes that are documented in TS 24.229. The OMR procedures use SDP offer/answer related procedures in RFC 3264 and in TS 24.229 in a backward-compatible manner.

Annex Q of TS 23.228 documents the architecture and call flows for OMR.

The OMR procedures in this document are applicable to the following IMS entities that perform as an IMS-ALG or UA according to TS 24.229 and that control media resources:
  • an IBCF acting as an IMS-ALG;
  • a P-CSCF acting as IMS-ALG;
  • an AS acting as B2BUA and adapting IMS-ALG procedures to control an MRF;
  • an AS acting as B2BUA and adapting UA procedures to control an MRF; and
  • an MGCF acting as UA.
Note 1:
An AS acting as B2BUA to perform application functions such as conferencing or announcements will normally perform separate originating and terminating UA procedures, treating the media resource as an endpoint. An AS acting as B2BUA offering transcoding options will typically follow IMS-ALG procedures.
Note 2:
The controlled media resource can be a TrGW, IMS-AGW, MRF, or a media function of the entity performing OMR.

The OMR procedures are not applicable for an UE.


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1 Scope    2 References    3 Definitions, symbols and abbreviations    3.1 Definitions    3.2 Symbols    3.3 Abbreviations    4 General    5 Common SDP Procedures    5.1 General    5.2 Encapsulation of previous SDP information    5.3 Determination of codec related SDP information associated to a previous realm instance    5.4 Modifying codec related information    5.5 Additional handling for SDP answer with actual configuration    5.6 Procedures specific to OMR attributes    5.7 Roaming architecture for voice over IMS with local breakout    5.8 II-NNI traversal scenario    6 IMS-ALG procedures    6.1 IMS-ALG handling of initial SDP offer    6.2 IMS-ALG handling of initial SDP answer    6.3 IMS-ALG OMR media resource operations    6.4 Handling of connected IP realms    7 UA Procedures    7.1 UA sending an initial SDP offer    7.2 UA receiving an initial SDP offer    7.3 UA receiving an initial SDP answer    7.4 UA OMR media resource operations    7.5 Handling of connected IP realms    8 Subsequent SDP offer/answer transactions    8.1 General    8.2 IMS-ALG and UA subsequent SDP offer procedures    8.3 IMS-ALG and UA subsequent SDP answer procedures    8.4 Handling media resources during a subsequent SDP offer/answer transaction    A Signalling flows    A.1 Scope of signalling flows    A.2 Introduction    A.3 Media bypassing all IMS-ALGs    A.4 IMS-ALG allocates a local transcoding MR when performing proactive transcoding without resource reservation    A.5 IMS-ALG bypasses an allocated transcoding MR    A.6 Loopback routeing via an intermediate network    B Change history   


1   Scope [R10]   PDF-p. 6
2   References [R10]
3   Definitions, symbols and abbreviations [R10]   PDF-p. 7
4   General [R10]
5   Common SDP Procedures [R10]   PDF-p. 9
6   IMS-ALG procedures [R10]
7   UA Procedures [R10]   PDF-p. 24
8   Subsequent SDP offer/answer transactions [R10]
A   Signalling flows [R10]   PDF-p. 29
B   Change history   PDF-p. 90

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