Section: 4.7.4 GPRS detach procedure 4.7.4.0 General
Content: The GPRS detach procedure is used: - to detach the IMSI for GPRS services only. Independent of the network operation mode, this procedure is used by all kind of GPRS MSs; - as a combined GPRS detach procedure used by GPRS MSs operating in MS operation mode A or B to detach the IMSI for GPRS and non-GPRS services or for non-GPRS services only, if the network operates in network operation mode I and no circuit-switched transaction is ongoing; - in the case of a network failure condition to indicate to the MS that a re-attach with successive activation of previously active PDP contexts shall be performed. In this case, the MS may also perform the procedures needed in order to activate any previously active multicast service(s); or - to detach the IMSI or IMEI for emergency bearer services. After completion of a GPRS detach procedure or combined GPRS detach procedure for GPRS and non-GPRS services the GMM context is released. An eCall only mobile station that is not capable of eCall over IMS shall not perform any kind of GPRS detach procedure. The GPRS detach procedure shall be invoked by the MS if the MS is switched off, the SIM/USIM card is removed from the MS or if the GPRS or non-GPRS capability of the MS is disabled. The procedure may be invoked by the network to detach the IMSI for GPRS services. The GPRS detach procedure causes the MS to be marked as inactive in the network for GPRS services, non-GPRS services or both services. If the detach procedure is triggered due to SIM/USIM removal, the MS shall indicate "switch off" in the detach type IE. If a detach is requested by the HLR for an MS that has a PDP context for emergency services, the SGSN shall not send a DETACH REQUEST message to the MS, and shall follow the procedure described in subclause 6.1.3.4.2 for an MS that has PDP contexts for emergency bearer services. When upper layers indicates that emergency bearer services are no longer required, the MS if still attached for emergency bearer services, may perform a detach followed by a re-attach to regain normal services, if the MS is in or moves to a suitable cell. In A/Gb mode, if the GPRS detach procedure is performed, the PDP contexts and the MBMS contexts, if any, are deactivated locally without peer to peer signalling between the SM and LLC entities in the MS and the network. In Iu mode, if the GPRS detach procedure is performed, the PDP contexts and the MBMS contexts, if any, are deactivated locally without peer to peer signalling between the SM entities in the MS and the network. If the MS supports S1 mode, the MS shall store the TIN in the non-volatile memory in the ME, as described in 3GPP TS 24.301[ Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3 ]  [120], annex C, for a subsequent attach procedure. The MS is allowed to initiate the GPRS detach procedure even if the timer T3346 is running. The network proceeds with the GPRS detach procedure even if NAS level mobility management congestion control is active.