6.2.7 QoS Packet Marking

23.3343GPPIP Multimedia Subsystem (IMS) Application Level Gateway (IMS-ALG) - IMS Access Gateway (IMS-AGW) interface: Procedures descriptionsRelease 17TS

This procedure is identical to that of clause 6.2.1 apart from the IMS-ALG optionally specifying the setting of the DSCP for outgoing packets on a termination. The DSCP value may be explicitly set by the IMS-AGW or else copied from that received in the corresponding received packet.

If differentiated services are required for the created termination, then the IMS-ALG shall include the information elements "DiffServ Code Point" and/or "DiffServ Tagging Behaviour" in the request sent to the IMS-AGW.

Subsequently, for all egress packets, the IMS-AGW shall set the DiffServ Code Point in the IP header as specified by the IMS-ALG:

– If the DiffServ Tagging Behaviour information element was received with a value to indicate that the DiffServ Code Point should be copied, then the DiffServ Code Point in the IP header of the egress packet is copied from the ingress packet.

– If the Diffserv Tagging Behaviour information element was not received, or was received with a value to indicate that the DiffServ Code Point should be set to a specific value, then:

– If the DiffServ Code Point information element was received, then the DiffServ Code Point in the IP header of the egress packet shall be set to the value received in the DiffServ Code Point information element.

– If the DiffServ Code Point information element was not received, then the DiffServ Code Point in the IP header of the egress packet shall be set to a configured default value.