E.5 IP version interworking in IMS

23.2283GPPIP Multimedia Subsystem (IMS)Release 18Stage 2TS

A PDP context & its associated additional PDP contexts (i.e. PDP contexts associated to the same IP address/prefix) support either PDP type IPv4 or IPv6 or IPv4v6. For communication with the IMS, the UE establishes an IPv4 PDN connection or an IPv6 PDN connection or an IPv4IPv6 PDN connection via PDP contexts/EPS bearers. Termination of this PDP context/EPS bearer will normally trigger de-registration of IMS application first. Hence, the PDP context/EPS bearer that has been established for IMS communication must be retained for the UE to establish a SIP session via the IMS with an IPv4 SIP client.

As such, any interworking on IP version on the application level (i.e. IMS & SIP) need to work with the architecture requirement from GPRS/EPS of maintaining the IP connectivity over GPRS/EPS by maintaining the PDP contexts/EPS bearers.

For IMS perspective, a user may be connected either to a home GGSN/P‑GW or a visited GGSN/P‑GW depending on the configuration as specified in TS 23.221 [7].