5.7 Functionality Needed for Mobile IPv4
23.0603GPPGeneral Packet Radio Service (GPRS)Release 17Service descriptionStage 2TS
To support the optional Mobile IP services, see TS 23.121 [54], efficiently by GPRS, Foreign Agent (FA) functionality needs to be provided in the GGSN. The interface between the GGSN and FA, including the mapping between the care of IP address and the GTP tunnel in the PLMN is not standardized as the GGSN and the FA are considered to be one integrated node.
Mobile IP service needs a Home Agent (HA) to anchor the IP session. The HA is a router that tunnels datagrams to/from an FA. The FA tunnels/de-tunnels the datagrams between the MS and the HA. In this case, the FA functionality resides in the GGSN. The location of the HA is outside the scope of the 3GPP specifications.
The FA and HA functionality is specified in RFC 3344 [46].
The Mobile IPv4 mobility management capabilities described in this clause are in addition to and distinct from the Mobile IP capabilities defined in TS 23.402 [90]. Support of Mobile IPv4 defined for the GGSN is retained in this specification for support of legacy terminals. Interworking between Mobile IPv4 support in the GGSN and MIPv4 as defined in TS 23.402 [90] is not defined for this release.