Step 1.
AF of content provider initiates MBS Session Update to a NEF/MBSF, e.g. to update MBS service area and/or update MBS Service Information (as defined in
clause 6.14), or to activate or deactivate an MBS session. AF may provide updated information for an MBS session (identified by MBS session ID) by sending an
Nnef_MBSSession_Update Request (MBS Session ID, [MBS Service Information], [MBS service area], [MBS session state (active/inactive)], [NR RedCap UE Information]).
If geographical area information or civic address information was provided by the AF as MBS service area, NEF/MBSF translates the MBS service area to Cell ID list or TAI list.
For broadcast communication, the AF may subsequently update
"NR RedCap UE Information" parameter.
Step 2.
NEF checks authorization of AF.
Step 3.
NEF/MBSF sends
Nmbsmf_MBSSession_Update Request to MB-SMF forwarding the updated information received from the AF in step 1. If the MBSF acts as the MBS security function for multicast as defined in
TS 33.501, it may provide an updated multicast session security context for the MBS session in the
Nmbsmf_MBSSession_Update Request.
If the MBS service area is not covered by the MB-SMF service area of the MB-SMF, the MB-SMF reduces the MBS service area to be within the MB-SMF service area and continues the procedure with the reduced MBS service area.
For broadcast communication, the NEF/MBSF forwards
"NR RedCap UE Information" parameter to the MB-SMF, if received.
Step 4.
The MB-SMF derives any updated QoS parameters locally under consideration of the updated MBS Service Information. This may lead to addition of new MBS QoS Flow(s), removal of existing MBS QoS Flow(s) or update of existing MBS QoS Flow(s).
Step 5-6.
MB-SMF may need to update MB-UPF, e.g. if new MBS QoS Flow is to be created, or existing MBS QoS Flow is to be deleted.
Step 7.
For broadcast communication, the MB-SMF continues the procedure towards the AMF and NG-RAN as specified in
clause 7.3.3. For multicast communication, the MB-SMF continues the procedure towards the AMF and NG-RAN as specified in
clause 7.2.5 (for service activation/deactivation),
clause 7.2.6 (for QoS updates and service area updates).
Step 8.
If an MBS service area is being updated, the MB-SMF stores the new service area in its profile at the NRF.
Step 9.
MB-SMF responds to the NEF/MBSF with a
Nmbsmf_MBSSession_Update Response ([Information of area reduction]).
If the MB-SMF reduces the MBS service area in step 3, the MB-SMF includes result information in the response indicating that the MBS service area cannot be covered by the MB-SMF service area of the MB-SMF, and includes the Information of area reduction that relates to the reduced MBS service area.
Step 10.
NEF/MBSF responds to the AF with a
Nnef_MBSSession_Update Response ([MBS service area information]).
If the NEF/MBSF receives the result information in step 9 indicating that the MBS service area cannot be covered by the MB-SMF service area of the MB-SMF, the NEF/MBSF includes that result information, and the Information of area reduction.