23.2053GPPBearer-independent circuit-switched core networkRelease 17Stage 2TS
If AoIP is supported by the MSC server, the Core Network side procedures described in 6.2.1 or 6.2.2 shall apply. For the access side termination, the exchange of IP addresses via call control procedures is described in this clause.
Before the MSC server sends the Assignment Request to the BSC, the MSC server requests the MGW to reserve an RTP bearer termination using the Reserve RTP Connection Point procedure. The MSC server requests the MGW to reserve an IP Address and UDP Port and also may indicate that the IP interface type is for A interface over IP. The MGW reserves the AoIP termination and indicates the IP address and UDP port number to the MSC server. MSC server then requests access bearer assignment using the provided IP address and UDP Port. When MSC server receives the BSSMAP ASSIGNMENT COMPLETE message, it shall send the BSC IP address and UDP Port to the MGW Access bearer termination using the Configure RTP Connection Point procedure.
The sequence is shown in figure 6.2.3/1.
Figure 6.2.3/1 Terminating Call Establishment For AoIP