IMS 5G PDU session establishment

Voice and video calls are use cases that need to be supported by every service provider network. The IP Multimedia Subsystem (IMS) enables these services in a telecom network. In this section, we will see how voice, video, and rich communication services are provided with the help of the IMS in 5G, which is very similar to the support of voice in 4G (VoLTE). Figure 7.12 shows the establishment of an IMS PDU session in 5G:

Figure 7.12 – IMS 5G PDU attach in 5G – part 1

Let’s look at these steps in detail:

Step 1: The UE initiates the N1 message with the PDU session establishment request by including a container identifier, P-CSCF IPv4/v6 Request contained within the ePCO (extended Protocol Configuration Options) IE, and DNN set to IMS.

Step 2: The AMF sends the Nsmf_PDUSession_CreateSM context request to the SMF by including N1 and N2 messages as multipart, along with the ePCO IE if it is received...