 (AIA) Update-Location-Request (ULR) Update-Location-Answer (ULA) Purge-UE-Request (PUR) Purge-UE-Answer (PUA) Insert-Subscriber-Data-Request (IDR) Insert-Subscriber-Data-Answer (IDA) Cancel-Location-Request (CLR) Cancel-Location-Answer (CLA) Delete-Subscriber-Data-Request (DDR) Delete-Subscriber-Data-Answer (DDA) Reset-Request (RSR) Reset-Answer (RSA) Notify-Request (NOR) Notify-Answer (NOA) Table 2.15. DIAMETER messages over S6a interface AIR and AIA messages allow an MME entity to retrieve the authentication data of the mobile (RAND, RES, AUTN and KASME). ULR and ULA messages allow: - to provide the HSS entity with the identity of the MME entity who attached the mobile and information on the mobile; - the MME entity to retrieve the profile mobile data. 62 VoLTE and ViLTE PUR and PUA messages are used to inform the HSS entity that MME entity deleted the mobile profile, after a long period of inactivity. CLR and CLA messages allow the HSS entity to delete the mobile profile stored in the MME entity. IDR and IDA messages allow the HSS entity updating mobile profile stored in the MME entity. DDR and DDA messages allow the HSS entity to remove elements of the mobile profile stored in the MME entity. RSR and RSA messages allow informing the MME entity of a restart of the HSS entity. NOR and NOA messages allow to inform the HSS entity on certain events on the mobile. 2.8.2. Application to IMS network Table 2.16 summarizes DIAMETER messages exchanged over Cx interface between, on the one hand, serving call session control function (S-CSCF) or interrogating-CSCF (I-CSCF), while on the other hand, the HSS entity. The same DIAMETER messages are exchanged over the Dx interface between, on the one hand, the S-CSCF or I-CSCF entities, and, on the other hand, the subscription locator function (SLF). Request Response Multimedia-Authentication-Request (MAR) Multimedia-Authentication-Answer (MAA) Server-Assignment-Request (SAR) Server-Assignment-Answer (SAA) Registration-Termination-Request (RTR) Registration-Termination-Answer