5.2 Summary

29.3343GPPIMS Application Level Gateway (IMS-ALG) – IMS Access Gateway (IMS-AGW)Iq InterfaceRelease 17Stage 3TS

This Profile describes the minimum mandatory settings and procedures required to fulfil the requirements of the Iq interface (see 3GPP TS 23.334 [23]):

– allocation and translation of IP addresses and port numbers (NA(P)T and NA(P)T-PT);

– opening and closing gates (i.e. packets filtering depending on "IP address / port");

– remote NA(P)T traversal;

– policing of incoming traffic;

– QoS packet marking for outgoing traffic;

– IP realm/domain indication;

– Hanging termination detection; and

– RTCP handling;

and when ATCF/ATGW is supported:

– handover of bearer connections between PS and CS access networks;

– IP version interworking; and

– audio transcoding;

and when WebRTC is supported:

– interworking for WebRTC audio, video and optionally MSRP data between WebRTC clients and non-WebRTC user equipment; and

– optionally transparent forwarding of WebRTC bearer traffic in case of end-to-end WebRTC calls between WebRTC IMS clients.

In addition, optional settings and procedures are described which fulfil optional features and where supported, the minimum mandatory settings within the optional procedures and packages are identified that must be supported in order to support that feature.

"Optional" or "O" means that it is optional for either the sender or the receiver to implement an element. If the receiving entity receives an optional element that it has not implemented it should send an Error Code (e.g. 445 "Unsupported or Unknown Property", 501"Not Implemented", etc.). "Mandatory" or "M" means that it is mandatory for the receiver to implement an element. Whether it is mandatory for the sender to implement depends on specific functions; detail of whether elements of the core protocol are mandatory to be sent are defined in the stage 2 procedures, stage 3 procedures and/or the descriptions of individual packages.

The setting or modification of elements described in the profile under the heading "Used in Command" has the meaning that the property can be set/modified with that command. The property may be present in other commands (in order to preserve its value in accordance with ITU-T Recommendation H.248.1 [10]) when those commands are used for other procedures that affect the same descriptor.