4 General

24.3043GPPMobility management based on Mobile IPv4Release 17Stage 3TSUser Equipment (UE) - foreign agent interface

4.1 Mobility management based on FACoA

MIPv4 is specified in IETF RFC 5944 [2] which provides two alternative modes of enabling a mobile node (UE) to acquire a care-of address for routing of datagrams:

– a "foreign agent care-of address" (FACoA) mode wherein a care-of address is provided by a FA through agent advertisement messages, or

– a "co-located care-of address" mode wherein a care-of address is acquired by the UE as a local IP address.

For the purpose of IP mobility management while accessing the EPC through a trusted non-3GPP access network, the FACoA mode enables the UE to register the IP address of the FA (FACoA) located within the non-3GPP access network with the UE’s HA for the routing of datagrams to the UE.

4.2 Identities

In order to support MIPv4 FA mode mobility management with the EPC, the network and mobile client shall use an NAI as described in 3GPP TS 23.003 [4] for user identification. The network and mobile client shall base the username part of the NAI on IMSI.

The network and UE shall use the Root NAI when the UE attempts a MIPv4 registration while attached to the HPLMN. The Root NAI format is specified in 3GPP TS 23.003 [4].

The network and UE shall use the Decorated NAI when the UE attempts a MIPv4 registration while attached to a VPLMN. The Decorated NAI format is specified in 3GPP TS 23.003 [4].

4.3 Multiple PDN connectivity

Following the establishment of a mobility binding to an initial PDN, the UE can request the establishment of a mobility binding with an additional PDN by including the APN of the desired PDN within a Service Selection extension defined in IETF RFC 5446 [5]. The Service Selection extension is included within the Registration Request (RRQ) message defined in IETF RFC 5944 [2]. The UE can repeat the process of sending an (RRQ) with a Service Selection extension to establish connectivity with additional PDNs.

4.4 MIPv4 security aspects

The procedures for bootstrapping of MIPv4 foreign agent care-of address (FACoA) security parameters are described in 3GPP TS 33.402 [6].

The MIPv4 security is based on the use of the authentication extensions defined in IETF RFC 5944 [2]. The MIPv4 signalling messages are protected between the UE and the HA using the Mobile-Home Authentication extension and optionally between the UE and the FA using the Mobile-Foreign Authentication extension.