Section: 6.1 GPRS Session management 6.1.1 General
Content: The main function of the session management (SM) is to support PDP context handling of the user terminal. Furthermore, the SM supports the MBMS context handling within the MS and the network, which allows the MS to receive data from a specific MBMS source. The SM comprises procedures for - identified PDP context activation, deactivation and modification; and - identified MBMS context activation and deactivation. SM procedures for identified access can only be performed if a GMM context has been established between the MS and the network. If no GMM context has been established, the MM sublayer has to initiate the establishment of a GMM context by use of the GMM procedures as described in chapter 4. After GMM context establishment, SM uses services offered by GMM (see 3GPP TS 24.007[ Mobile radio interface signalling layer 3; General Aspects ]  [20]). Ongoing SM procedures are suspended during GMM procedure execution. The SM procedures for identified MBMS context activation and deactivation can only be performed, if in addition to the GMM context the MS has a PDP context activated. In Iu mode only, integrity protected signalling (see subclause 4.1.1.1.1 of the present document and in general, see 3GPP TS 33.102[ 3G security; Security architecture ]  [5a]) is mandatory. In Iu mode only, all protocols shall use integrity protected signalling. Integrity protection of all SM signalling messages is the responsibility of lower layers. It is the network which activates integrity protection. This is done using the security mode control procedure (3GPP TS 25.331[ None ]  [23c] and 3GPP TS 44.118[ None ]  [111]). For the session management protocol, the extended TI mechanism may be used (see 3GPP TS 24.007[ Mobile radio interface signalling layer 3; General Aspects ]  [20]).