Section: 17.5.1 Service activation
Content: The multicast MBMS bearer service activation procedure registers the user in the network to enable the reception of data from a specific multicast MBMS bearer service Figure 26; Activation of an MBMS multicast service 1. The GGSN receives an IGMP (IPv4) or MLD (IPv6) Join message from a UE, over the default PDP context to signal its interest in receiving a particular multicast MBMS bearer service identified by an IP multicast address. 2. The GGSN sends an AAR seeking authorization for the activating UE to receive data from a particular service. 3. The authorization decision is provided in the AAA together with the APN to be used for creation of the MBMS UE context. If the AAA indicates that the UE is not authorized to receive the MBMS data the process terminates with no additional message exchange. 4. The GGSN sends an MBMS Notification Request (IP multicast address, APN, Linked NSAPI) to the SGSN. Linked NSAPI is set equal to the NSAPI of the PDP context over which the Join request was received. The IP multicast address is the one requested by the UE in the Join request. The APN may be different from the APN to which the default PDP context has been activated. In any case, the APN may resolve to a GGSN that is different from the GGSN receiving the IGMP/MLD Join request. The GGSN starts a MBMS Activation Timer as GGSN may receive no response, e.g. in case SGSN or UE does not support MBMS. 5. The SGSN sends a MBMS Notification Response (Cause) to the GGSN that sent the MBMS Notification Request, where Cause shall indicate successful or unsuccessful MBMS context activation for the reason of SGSN or UE . Upon reception of the response message with Cause indicating unsuccessful operation or time-out of the MBMS Activation Timer in the GGSN, the GGSN may fallback to IP multicast access as defined in clause 11.7. 6. The SGSN creates an MBMS UE context and sends a Create MBMS Context Requests (IP multicast address, APN, RAI) to the GGSN. That GGSN may be different from the GGSN receiving the IGMP/MLD Join request. 7. The GGSN sends an AAR seeking authorization for the activating UE. 8. The authorization decision is provided in the AAA 9. If the GGSN does not have the MBMS Bearer Context information for this MBMS bearer service, i.e. the GGSN was not yet registered, the GGSN sends a AAR to the BM-SC. See subclause 17.5.4 "Registration Procedure". If no TMGI has been allocated for this MBMS bearer service, the BM-SC will allocate a new TMGI. This TMGI will be passed to GGSN via the AAA message. 10. The BM-SC responds with a AAA containing the MBMS Bearer Context information for this MBMS bearer service and adds the identifier of the GGSN to the "list of downstream nodes" parameter in its MBMS Bearer Context. See subclause 17.5.4 "Registration Procedure". 11. The GGSN creates an MBMS UE context and sends a Create MBMS Context Response to the SGSN