Section: 4.7.1.4.1 Radio resource sublayer address handling (A/Gb mode only)
Content: This subclause describes how the RR addressing is managed by GMM. For the detailed coding of the different TLLI types and how a TLLI can be derived from a P-TMSI, see 3GPP TS 23.003[ Numbering, addressing and identification ]  [10]. If the MS is configured for "AttachWithIMSI" as specified in 3GPP TS 24.368[ Non-Access Stratum (NAS) configuration Management Object (MO) ]  [135] or 3GPP TS 31.102[ Characteristics of the Universal Subscriber Identity Module (USIM) application ]  [112] and is entering a new PLMN which is neither the registered PLMN nor in the list of equivalent PLMNs, the MS should proceed as specified for case ii) below and use a randomly selected random TLLI for the transmission of the ATTACH REQUEST message. For all other cases, the MS shall determine the TLLI as follows: For an MS not supporting S1 mode, two cases can be distinguished: - a valid P-TMSI is available in the MS; or - no valid P-TMSI is available in the MS. i) valid P-TMSI available If the MS has stored a valid P-TMSI, the MS shall derive a foreign TLLI from that P-TMSI and shall use it for transmission of the: - ATTACH REQUEST message of any GPRS combined/non-combined attach procedure; other GMM messages sent during this procedure shall be transmitted using the same foreign TLLI until the ATTACH ACCEPT message or the ATTACH REJECT message is received; and - ROUTING AREA UPDATE REQUEST message of a combined/non-combined RAU procedure if the MS has entered a new routing area, or if the GPRS update status is not equal to GU1 UPDATED. Other GMM messages sent during this procedure shall be transmitted using the same foreign TLLI, until the ROUTING AREA UPDATE ACCEPT message or the ROUTING AREA UPDATE REJECT message is received. After a successful GPRS attach or routing area update procedure, independent of whether a new P-TMSI is assigned, if the MS has stored a valid P-TMSI then the MS shall derive a local TLLI from the stored P-TMSI and shall use it for addressing at lower layers. NOTE 1: Although the MS derives a local TLLI for addressing at lower layers, the network should not assume that it will receive only LLC frames using a local TLLI. Immediately after the successful GPRS attach or routing area update procedure, the network must be prepared to continue accepting LLC frames from the MS still using the foreign TLLI. ii) no valid P-TMSI available When the MS has not stored a valid P-TMSI, i.e. the MS is not attached to GPRS, the MS shall use a randomly selected random TLLI for transmission of the: - ATTACH REQUEST message of any combined/non-combined GPRS attach procedure. The same randomly selected random TLLI value shall be used for all message retransmission attempts and for the cell updates within one attach attempt. Upon receipt of an ATTACH REQUEST message, the network shall assign a P-TMSI to the MS. The network derives a local TLLI from the assigned P-TMSI, and transmits the assigned P-TMSI to the MS. Upon receipt of the assigned P-TMSI, the MS shall derive the local TLLI from this P-TMSI and shall use it for addressing at lower layers. NOTE 2: Although the MS derives a local TLLI for addressing at lower layers, the network should not assume that it will receive only LLC frames using a local TLLI. Immediately after the successful GPRS attach, the network must be prepared to continue accepting LLC frames from the MS still using the random TLLI. In both cases the MS shall acknowledge the reception of the assigned P-TMSI to the network. After receipt of the acknowledgement, the network shall use the local TLLI for addressing at lower layers. For an MS supporting S1 mode, the following five cases can be distinguished: a) the TIN indicates "P-TMSI" or "RAT-related TMSI" and the MS holds a valid P-TMSI and a RAI; b) the TIN indicates "GUTI" and the MS holds a valid GUTI allocated by an MME; c) the TIN is deleted and the MS holds a valid P-TMSI and RAI; d) the TIN is deleted and the MS holds a valid GUTI allocated by an MME, but no valid P-TMSI and RAI; or e) none of the previous cases is fulfilled. In case a) the MS shall derive a foreign TLLI from the P-TMSI and proceed as specified for case i) above. In case b), the MS shall derive a P-TMSI from the GUTI and then a foreign TLLI from this P-TMSI and proceed as specified for case i) above. NOTE 3: The mapping of the GUTI to the P-TMSI is specified in 3GPP TS 23.003[ Numbering, addressing and identification ]  [10]. In case c) the MS shall derive a foreign TLLI from the P-TMSI and proceed as specified for case i) above. In case d) the MS shall derive a P-TMSI from the GUTI and then a foreign TLLI from this P-TMSI and proceed as specified for case i) above. In case e) the MS shall proceed as as specified for case ii) above. For transmission of an ATTACH REQUEST message, or a ROUTING AREA UPDATE REQUEST message after a routing area change, the MS also provides the lower layers with the DCN-ID according to the following rules: a) if a DCN-ID for the PLMN code of the selected PLMN is available in the MS, the MS shall provide this DCN-ID to the lower layers; or b) if no DCN-ID for the PLMN code of the selected PLMN is available but a Default_DCN_ID value is available in the MS, as specified in 3GPP TS 24.368[ Non-Access Stratum (NAS) configuration Management Object (MO) ]  [135] or in USIM file NASCONFIG as specified in 3GPP TS 31.102[ Characteristics of the Universal Subscriber Identity Module (USIM) application ]  [112], the MS shall provide the Default_DCN_ID value to the lower layers.