6.2.19 Application-aware MSRP interworking at the IMS-AGW

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:

– indicating "TCP/MSRP" or "TCP/TLS/MSRP" (if e2ae media security is applied) as transport protocol to the IMS‑AGW;

– configuring the IMS-AGW to apply application-aware MSRP interworking; and

– providing the SDP "a=path" attribute, as received in SIP/SDP signalling, to the IMS‑AGW as "MSRP Path" with the remote descriptor of the corresponding call leg.

The IMS‑AGW applies application-aware MSRP interworking if being instructed from the IMS-ALG. Support of dynamic instructions from the IMS-ALG is optional.

If the IMS-AGW applies application-aware MSRP interworking, it modifies the MSRP "To-Path" header field in MSRP packets by replacing the IP address and TCP port of the only entry with the corresponding information in the "MSRP path" provided by the IMS_ALG while retaining the MSRP session ID part of the entry as received in the MSRP "To-Path" and then forward the MSRP data without further modification.