Content for TS 23.334 Word version: 17.2.0

1… 4… 5… 5.11… 5.12… 5.14… 5.18… 5.19… 5.20… 5.21… 6… 6.1.6… 6.1.11… 6.2… 6.2.10… 6.2.10.3.1.2 6.2.10.3.2 6.2.10.4… 6.2.10.4.3… 6.2.10.5 6.2.10.6… 6.2.10A… 6.2.13… 6.2.14… 6.2.14.3 6.2.14.4… 6.2.15… 6.2.17… 6.2.17.3… 6.2.17.5… 6.2.18… 6.2.20 6.2.21… 6.2.22… 6.2.22.3… 6.2.22.3.2 6.2.23 6.2.24 6.2.25 7 8… 8.3 8.4 8.5… 8.23…

6.2.15 Multimedia Priority Congestion Control Procedures 6.2.15.1 General 6.2.15.2 IMS-AGW Resource Congestion in ADD response, request is queued 6.2.15.3 IMS-AGW Resource Congestion in ADD response, IMS-ALG seizes new IMS-AGW 6.2.15.4 IMS-AGW Priority Resource Allocation 6.2.15.5 IMS-AGW Priority User Data marking 6.2.15.6 IMS-AGW Priority Modification 6.2.16 Coordination of Video Orientation
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6.2.15 Multimedia Priority Congestion Control Procedures |R11| p. 144

6.2.15.1 General p. 144

The IMS-ALG and IMS-AGW may support the priority treatment of a call/session identified as an MPS call/session. This clause describes the Iq signalling procedures and their interactions with SIP signalling in the control plane and with user plane procedures to support the requirements for Multimedia Priority Service. These Iq signalling procedures may or may not apply depending on the network configuration (e.g. whether the IMS-AGW is shared by multiple IMS-ALGs or whether the IMS-ALG controls multiple IMS-AGWs for a given route - Media Gateway Group).

The IMS-ALG can receive a SIP INVITE with MPS priority information (see clause 5.21 of TS 23.228).

6.2.15.2 IMS-AGW Resource Congestion in ADD response, request is queued p. 144

If the IMS-ALG requests a resource via the procedure Reserve and Configure AGW Connection Point or Reserve AGW Connection Point and receives an error indicating that the requested resource could not be seized (e.g. H.248 error code #510 "insufficient resources") and the IMS-ALG does not have alternative IMS-AGW through which it can route the call it queues the priority session and gives it priority over any further Reserve and Configure AGW Connection Point or Reserve AGW Connection Point procedures for lower priority sessions towards this IMS-AGW until the requested resource for this queued session is successful seized. The example sequence is shown in Figure 6.2.15.2.1.

Copy of original 3GPP image for 3GPP TS 23.334, Fig. 6.2.15.2.1: Request to reserve IMS-AGW MPS Priority call resources when IMS-AGW is congested

Figure 6.2.15.2.1: Request to reserve IMS-AGW MPS Priority call resources when IMS-AGW is congested
(⇒ copy of original 3GPP image)

6.2.15.3 IMS-AGW Resource Congestion in ADD response, IMS-ALG seizes new IMS-AGW p. 145

If the IMS-ALG requests a resource via the procedure Reserve and Configure AGW Connection Point or Reserve AGW Connection Point and receives an error indicating that the requested resources could not be seized (e.g. H.248 error code #510 "insufficient resources") and Media Gateway Groups are implemented it should seize a new IMS-AGW from the same Media Gateway Group before resorting to any queuing of the priority session (as described in clause 6.2.15.2) to enable the MPS call/session to proceed as early as possible.

6.2.15.4 IMS-AGW Priority Resource Allocation p. 145

If the IMS-AGW supports the Priority information (e.g. determined through provisioning or package profile) the IMS-ALG requests a resource via the procedure Reserve and Configure AGW Connection Point or Reserve AGW Connection Point and includes the Priority information. The IMS-AGW may then provide priority allocation of resources once a congestion threshold is reached. If the IMS-AGW is completely congested it shall indicate this to the IMS-ALG as described in clause 6.2.15.2. The example sequence is shown in Figure 6.2.15.4.1.

Copy of original 3GPP image for 3GPP TS 23.334, Fig. 6.2.15.4.1: Request to reserve IMS-AGW MPS Priority call resources when IMS-AGW is congested, priority resources are allocated

Figure 6.2.15.4.1: Request to reserve IMS-AGW MPS Priority call resources when IMS-AGW is congested, priority resources are allocated
(⇒ copy of original 3GPP image)

6.2.15.5 IMS-AGW Priority User Data marking p. 146

The IMS-ALG may request the streams associated to an MPS Priority Call to be marked with certain priority code point as described in clause 6.2.7. The IMS-AGW shall then mark each IP packet header accordingly. The example sequence is shown in Figure 6.2.15.5.1.

Copy of original 3GPP image for 3GPP TS 23.334, Fig. 6.2.15.5.1: Request to reserve IMS-AGW call resources and apply DCSP marking for MPS

Figure 6.2.15.5.1: Request to reserve IMS-AGW call resources and apply DCSP marking for MPS
(⇒ copy of original 3GPP image)

The IMS-AGW may also provide priority allocation for resources requested via a subsequent Configure AGW Connection Point procedure not including Priority information if the related context has been marked with priority information during the Reserve AGW Connection Point or Reserve and Configure AGW Connection Point procedure.

6.2.15.6 IMS-AGW Priority Modification p. 146

If the IMS-ALG seized an IP termination for a priority call/session with a default priority and subsequently needs to modify the priority information previously communicated to the IMS-AGW (e.g. subject to subsequent authorisation by an authorisation point, see clause 4.11 of TS 24.229), the IMS-ALG may modify the existing IP termination for the MPS call/session with the actual priority and, if DiffServ is used, provision a suitable DSCP marking for the updated MPS priority level to the IMS-AGW via the Configure AGW Connection Point Procedure.

6.2.16 Coordination of Video Orientation |R12| p. 147

Figure 6.2.16.1 shows the message sequence chart example for indicating extended RTP header for Coordination of Video Orientation.

Copy of original 3GPP image for 3GPP TS 23.334, Fig. 6.2.16.1: Procedure to indicate RTP extension header for CVO

Figure 6.2.16.1: Procedure to indicate RTP extension header for CVO
(⇒ copy of original 3GPP image)

This procedure is identical to that of clause 6.2.1 apart from the IMS-ALG optionally requesting the IMS-AGW to support the RTP Header Extension capability as defined in RFC 5285.

NOTE:

If the IMS-ALG receives an SDP answer, which includes the "a=extmap" attribute with a CVO URN with a granularity that the IMS-AGW has not included in its response, or if the SDP answer does not include any "a=extmap" CVO related attribute, it is not necessary to modify the IMS-AGW settings for this reason alone. Doing that would only add unnecessary signalling without requiring any action or changes in the IMS-AGW. However, if the IMS-ALG needs to modify the media attributes for other purposes, in particular due to transcoding, then the IMS-AGW is updated in accordance with the received SDP answer, that is, either with the received CVO related "a=extmap" attribute if present in the received SDP answer or without it if not included in the received SDP answer (thus removing the requirement for supporting "a=extmap" and for sending the header and CVO bits for the transcoded stream).