6a.4.7 Remote party initiated add new media

23.2373GPPIP Multimedia Subsystem (IMS) Service ContinuityRelease 17Stage 2TS

The following is an example of an information flow where remote party wants to modify an existing session with UE-1 to add Media Flow-B. In this information flow, UE-1 and UE-2 belong to the same user subscription. UE-1 is the Controller UE and UE-2 is a Controllee UE. If UE-2 is not involved in the Collaborative Session controlled by UE-1 before the media addition, there is at least another Controllee UE involved in the Collaborative Session before the media addition which is not shown in the information flow.

Figure 6a.4.7-1: Remote party initiated add new media

1. Remote party sends an Add Media request to add Media Flow-B to an existing session between UE-1 and remote party as per TS 23.228 [4].

2. SCC AS forwards the Add Media request to UE-1 according to the procedures defined in TS 23.228 [4].

Step 3a is for the case Controller UE wants to add Media Flow-B to itself.

3a. The session setup is completed. The new Media Flow-B will after this be established between UE-1 and remote party, and be involved in the Collaborative Session controlled by UE-1.

Steps 3b and 5b are for the case Controller UE wants to add Media Flow-B to a different UE while retaining control for the added media.

3b. Controller UE-1 sends an IUT-Redirect-Media request to SCC AS. The IUT-Redirect-Media request needs to include at least the following information:

– identify that Media Flow-B needs to be redirected to UE-2.

4b. SCC AS performs authorization as specified in clause 6a.12, then sends an Add Media Flow-B to UE-2.

5b. The session setup is completed. When the add media operation is completed, there is Media Flow-B between UE-2 and remote party. There is a Collaborative Session established between UE-1 and UE-2. The Media-B is controlled by UE-1.

NOTE 1: If UE-2 was not involved in the Collaborative Session controlled by UE-1 before the media addition, UE‑2 becomes a Controllee UE when the media addition is completed.

NOTE 2: If remote party wants to add more than one media flows to an existing session, these media flows can be distributed to several different UEs by repeating the above steps 3b-5b.