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.
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
The controlled media resource can be a TrGW, IMS-AGW, MRF, or a media function of the entity
The OMR procedures are not applicable for an UE.