Section: 6.1.2 TMSI reallocation procedure
Content: The purpose of the mechanism described in this subsection is to allocate a new TMSI/LAI pair to a user by which he may subsequently be identified on the radio access link. The procedure should be performed after the initiation of ciphering. The ciphering of communication over the radio path is specified in clause 6.6. The allocation of a temporary identity is illustrated in Figure 3. Figure 3: TMSI allocation The allocation of a temporary identity is initiated by the VLR. The VLR generates a new temporary identity (TMSIn) and stores the association of TMSIn and the permanent identity IMSI in its database. The TMSI should be unpredictable. The VLR then sends the TMSIn and (if necessary) the new location area identity LAIn to the user. Upon receipt the user stores TMSIn and automatically removes the association with any previously allocatedTMSI. The user sends an acknowledgement back to the VLR. Upon receipt of the acknowledgement the VLR removes the association with the old temporary identity TMSIo and the IMSI (if there was any) from its database.