Section: 4.3.3.2 Identification response by the mobile station
Content: The mobile station shall be ready to respond to an IDENTITY REQUEST message at any time whilst a RR connection exists. Upon receipt of the IDENTITY REQUEST message the mobile station shall send an IDENTITY RESPONSE message. The IDENTITY RESPONSE message shall contain the identification parameters as requested by the network. Upon receipt of the IDENTITY REQUEST message with the Identity type IE indicating that P-TMSI, RAI and P-TMSI signature are being requested, an MS that supports S1 mode shall handle the IDENTITY RESPONSE message as follows: - If the TIN indicates "GUTI" and the MS holds a valid GUTI allocated by an MME, the MS shall map the GUTI into a P-TMSI, P-TMSI signature and RAI as specified in 3GPP TS 23.003[ Numbering, addressing and identification ]  [10]. The MS shall indicate the P-TMSI in the Mobile identity IE. In addition, the MS shall include the mapped RAI in the Routing area identification IE and the mapped P-TMSI signature in the P-TMSI signature IE. In addition, the MS shall include the P-TMSI type IE with P-TMSI type set to "mapped P-TMSI". - If the TIN indicates "P-TMSI" or "RAT-related TMSI" and the MS holds a valid P-TMSI and RAI, the MS shall indicate the P-TMSI in the Mobile identity IE and shall indicate the RAI in the Routing area identification IE. In addition, the MS shall include the P-TMSI type IE with P-TMSI type set to "native P-TMSI". If the MS holds a valid P-TMSI signature, it shall include it in the P-TMSI signature IE. If the MS does not support S1 mode, it shall handle the IDENTITY RESPONSE message as follows: - If the MS holds a valid P-TMSI and RAI, the MS shall indicate the P-TMSI in the Mobile identity IE and shall indicate the RAI in the Routing area identification IE. In addition, the MS shall include the P-TMSI type IE with P-TMSI type set to "native P-TMSI". If the MS holds a valid P-TMSI signature, it shall include it in the P-TMSI signature IE. Upon receipt of the IDENTITY RESPONSE message, the network shall stop timer T3270.