Section: 17.3 MBMS session start / update/ stop
Content: The MBMS session start shall be used by the BM-SC to trigger the bearer resource establishment and announce the arrival of data for a MBMS bearer service (along with the attributes of the data to be delivered e.g. QoS or MBMS service area) to every GGSN that will deliver the MBMS bearer service. The MBMS session start shall also be used by the BM-SC to indicate to GGSN if IP multicast mechanism should be used for user plane data distribution to UTRAN. The MBMS session update shall be used by the BM-SC to trigger the update of MBMS session attributes in the affected GGSNs. The MBMS session stop shall be used by the BM-SC to indicate the end of the data stream for an MBMS bearer service to every GGSN that has been delivering the MBMS bearer service.