23 Roles for collaborative session media modification

24.3373GPPIP Multimedia (IM) Core Network (CN) subsystem IP Multimedia Subsystem (IMS) inter-UE transferRelease 17Stage 3TS

23.1 Introduction

This clause specifies the procedures for collaborative session media modification including controller UE initiated media modification on controllee UE and controllee UE initiated media modification on itself.

23.2 Controller UE initiated media modification on controllee UE

23.2.1 Controller UE

The controller UE procedures for modifying media on controllee UE by the controller UE is the same as the procedure described in subclause 11.2.2.1 with exception that the controller UE additionally sets the port numbers for the media types of the media components (in the hname "body" URI header field in the SIP URI in the Refer-To header field of the SIP REFER request) which are being modified on the controllee UE to values from the corresponding media lines received during the last successful SDP offer and answer exchange with the remote party.

23.2.2 SCC AS serving for collaborative session

The SCC AS procedures for modifying media on controllee UE by the controller UE is the same as the procedure described in subclause 11.3.3.

23.3 Controllee UE initiated media modification on itself

23.3.1 Controllee UE

If the controllee UE wants to modify the characteristics of a media component on itself within a collaborative session, the controllee UE shall follow the procedures defined in 3GPP TS 24.229 [7] for modifying media.

23.3.2 SCC AS serving the collaborative session

When SCC AS receives a SIP re-INVITE request within an existing dialog from the controllee UE to modify a media component on itself, the SCC AS shall send a SIP re-INVITE request to the remote UE. The SCC AS shall construct the SDP information in the SIP re-INVITE request as follows:

1) set the media information of the media established in the controllee UE as the same in the SIP re-INVITE request received from the controllee UE; and

2) include the SDP information for all other media components in the collaborative session as received during the last successful SDP offer-answer exchange from the remote UE.

Upon receiving SIP 200 (OK) response with the SDP answer from the remote UE, the SCC AS shall send:

1) a SIP ACK request to the remote UE; and

2) a SIP 200 (OK) response to the controllee UE with an SDP answer that only contains the media component on the controllee UE.