6a.4.4 Controller UE Initiated Release Media (media flow on the Controllee UE)

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

6a.4.4.1 Controller UE and Controllee UE belong to the same subscription

The information flow shows the Controller UE releasing a media flow from a Controllee UE. As a pre-requisite, there exists a Collaborative Session with two media flows, flow–A on the Controller UE (UE-1) and Flow–B on the Controllee UE (UE-2).

Figure 6a.4.4.1-1: Controller UE Initiated Media release – media flow on Controllee UE (Controller and Controllee belong to the same IMS subscription)

1. UE-1 sends a Release Media request to the SCC AS to remove Media-A from the Collaborative Session. The request includes the information pertaining to media flow -B:

– identify that the released media is Media Flow-B;

– identify that the released media is on UE-2;

– keep the control of Collaborative Session in UE-1.

2. The SCC identifies media flow B as associated with UE-2 (controllee UE) and sends the Release Media Request to UE-2. The request identifies the media flow–B that needs to be removed and the media flow is removed. If no more media flows remain on UE-2 that are participating in the Collaborative Session, the SCC AS releases the access leg from UE-2.

3. UE-2 sends back Release Media response back to SCC AS.

4. The SCC AS updates the Remote Leg with media flow–B removed.

Step 2 and step 4 may be executed in any order.

5. The SCC AS sends release media response to UE-1.

If UE-2 has left the Collaborative Session at step 2 and no other Controllee UE remain in this Collaborative Session, this Collaborative Session becomes a normal IMS session.

6a.4.4.2 Controller UE and Controllee UE belong to different subscriptions

The following information flow shows the Controller UE releasing a media flow from the Controllee UE that belongs to different subscriptions. As a pre-requisite, there exists a Collaborative Session with two media flows, Media–A on the Controller UE (UE-1) and Media–B on the Controllee UE (UE-2). Furthermore, Controller UE and Controllee UE profiles are stored on different S-CSCFs, S‑CSCF-1 and S-CSCF-2, respectively.

Figure 6a.4.4.2-1: Controller initiated Release of media from Controllee UE (Controller and Controllee belong to different IMS subscriptions)

1. Controller UE-1 sends a Release media request to SCC AS-1 to release Media-B on Controllee UE-2. The Collaborative Session request includes enough information for the network to:

– identify that the media to be released is Media-B;

– identify that the media to be held is on Controllee UE-2;

– identify the session that contains of the media flow to be released;

– keep the control of the Collaborative Session in Controller UE-1.

2a. S-CSCF-1 forwards the Release Media request to SCC AS-1.

2b. SCC AS-1 verifies that UE-1 is a Controller and therefore is authorized to release the media from a Controllee UE with a user belonging to another subscription.

2c. SCC AS-1 sends a Release Media request towards UE-2 to release Media-B on UE-2. The Collaborative Session request includes enough information for the network to:

– identify the source of the release media request as UE-1;

– identify that the media flow to be released is Media-B;

– identify that the source of the media flow to be released is Controllee UE-2.

3. S-CSCF-1 forwards the Release Media request towards S-CSCF-2.

4. S-CSCF-2 forwards the Release Media Request towards the Controllee.

5. Controllee UE-2 provides the Release Media Response to the S-CSCF-2.

6-7. S-CSCF-2 forwards the Release Media Response to SCC-AS-1.

8. The SCC AS-1 updates the remote leg of the collaborative session with Media-B released.

9-10. The SCC AS-1 informs the Controller UE-1 via the S-CSCF-1 of successfully releasing Media-B from Controllee UE 2. Steps 9-10 could be performed in parallel to Step 10.