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Core network aspects 1

Appendix II

Mapping between functions defined in this Recommendation
and IETF entities

(This appendix does not form an integral part of this Recommendation)

II.1 The IETF mobility architectures
The IETF has been working on mobility at the IP level for several years, beginning with MIPv4
([b-IETF RFC 3344]), working through MIPv6 ([b-IETF RFC 3775]), and a variety of optimizations and
extensions including proxy mobile IP (PMIP) ([b-IETF RFC 5213]) and hierarchical mobile IP (HMIP) ([b-
IETF RFC 4140]). Each of the variants just mentioned introduces its own architectural elements. The only
network element common to all of these architectures, which are individually described below, is the home
agent. However, this appendix demonstrates that the IETF architectural components can be shown to share
certain sets of functions in common. These functions are the same as the ones identified in clause 6.4.
Note that each of these architectures includes the mobile node and the correspondent node as well as the
network elements it identifies. For our purpose, the mobile node can be identified with the UE, and the
correspondent node, most conveniently, with the SCF.
II.1.1 MIPv4

Mobile IP v4 (MIPv4) requires the UE to support functions specific to mobility. It identifies two network
entities: the foreign agent (FA) and the home agent (HA). The FA can be collocated with the UE, creating a
scenario similar to MIPv6. The IETF architecture for MIPv4 is shown in Figure II.1.

Local domain Home domain

AAAL AAAH

MN FA HA

AAA signalling
MIP signalling Y.2018(09)_FII.1

Figure II.1 – MIPv4 architecture according to the IETF

Mobile IP requires every registration to be handled between the home agent (HA) and the foreign agent (FA),
as shown by the dashed line in Figure II.1. During the initial registration, some operations happen (such as
allocating HoA, HA address, derive MSAs) that enable the home agent and foreign agent to perform
subsequent mobile IP registrations. After the initial registration, the AAAH and AAAL in Figure II.1 will not be
needed, and subsequent mobile IP registrations will only follow the lower control path between the foreign
agent and the home agent.

Table II.1 lists the functions that must be supported by the FA and the HA, and matches these functions to
those defined in clause 6.4.

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