 BEARER RESPONSE Figure 3.1. Mobile attachment to EPS network The EMM ATTACH message carries the ESM PDN CONNECTIVITY REQUEST message. The EMM ATTACH REQUEST message is carried by the RRC ConnectionSetupComplete message on the LTE-Uu radio interface and the S1-AP INITIAL UE MESSAGE message on the S1-MME interface. Basic Procedures The S1-AP UE INITIAL MESSAGE message contains the identities of TAI and ECGI. 2) Upon receipt of the EMM ATTACH REQUEST message, the MME entity requests the home subscriber server (HSS) entity for the cryptographic data of the mobile in the DIAMETER AIR (Authentication-Information- Request) message. 3) The HSS entity generates cryptographic data using a random number RAND and the key Ki of the mobile and sends them to the MME entity in the DIAMETER AIA (Authentication-Information-Answer) message. The cryptographic data contain the random number (RAND), the mobile authentication code (RES), the network authentication code (AUTN) and the KASME key. The MME entity derives the KASME key to generate the CKNAS, IKNAS and KeNB keys: - the CKNAS key is used to encrypt the NAS message; - the IKNAS key is used to control the integrity of the NAS message; - the KeNB key is transferred to the eNB entity. 4) The MME entity transmits the EMM AUTHENTICATION REQUEST message containing the random number (RAND) and the network authentication code (AUTN) to the mobile. The mobile calculates locally from its secret Ki stored in the universal services identity module (USIM) of its universal integrated circuit card (UICC) and the RAND random number received, the key KASME, its authentication code (RES) and that of the network (AUTN) which it compares to the value received. If the two values are identical, the network is authenticated. 5) The mobile responds to the MME entity with the EMM AUTHENTICATION RESPONSE message containing the RES authentication code. The MME entity compares the RES values received from the mobile and HSS entity. If the values are the same, the mobile is authenticated. VoLTE and ViLTE