5.4 IP addressing and routing for access to IM-subsystem services

23.2213GPPArchitectural requirementsRelease 17TS

This clause deals with a UE accessing IM CN subsystem services via EPS or GPRS.

A UE accessing IM CN Subsystem services requires an IP address that is logically part of the IM CN subsystem IP Addressing Domain. This is established using an appropriate PDP or EPS Bearer context. It is possible to connect to a P‑GW/GGSN either in the VPLMN or the HPLMN. For routing efficiency this context may benefit from being connected through a P‑GW/GGSN in the visited network. The connection between the UE and the IM CN subsystem (where the P‑GW/GGSN is either in the Home or the Visited network) is shown below:

Figure 5-5: UE Accessing IM Subsystem Services with P-GW/GGSN in the Visited network via Visited Network IM subsystem

Figure 5-5a.1: UE Accessing IM Subsystem Services with P-GW/GGSN in the Visited network

Figure 5-5a: UE Accessing IM CN subsystem Services with P-GW/GGSN in the Home network

The ability of the User plane and the Control Plane for a single IMS session being able to pass through different P‑GWs/GGSNs is not defined in this release.