Section: 7.3.22 UE Registration Query Response
Content: The UE Registration Query Response message shall be sent as a response to a UE Registration Query Request, to report whether the inquired UE is registered in the MME and if so, with which Core Network Operator, as specified in the clause 7.1.6 of 3GPP TS 23.251[ Network sharing; Architecture and functional description ]  [55]. Possible Cause values are specified in Table 8.4-1. Message specific cause values are: - "Request accepted", to be used when the UE is registered in the MME - "IMSI/IMEI not known", to be used when the UE is not registered in the MME. The IMSI received in the UE Registration Query Request message shall be included in the response, to allow correlation in the SGSN. The Selected Core Network Operator Identifier identifies the core network operator currently serving the UE, and shall be included if the inquired UE is registered in the MME. Table 7.3.22-1 specifies the presence of IEs in this message. Table 7.3.22-1: Information Elements in UE Registration Query Response