RFC 5944

IP Mobility Support for IPv4, Revised
Standards Track Obsoletes: RFC 3344
November 2010
RFC Library > IP Mobility > RFC 5944
Abstract: Mobile IPv4 (MIPv4) allows an IPv4 node to change its point of network attachment while maintaining its home IP address and active connections. In 3GPP, MIPv4 concepts influenced EPC mobility design and are used for CDMA/3GPP2 interworking.
Canonical source: https://www.rfc-editor.org/rfc/rfc5944  |  IETF Datatracker

1. Introduction

▶

Mobile IPv4 provides transparent host mobility in IPv4 networks. A mobile node (MN) is assigned a permanent home address on its home network. When away, a Home Agent (HA) tunnels packets to the MN's current location (care-of address) via an IP-in-IP tunnel.

In 3GPP context, MIPv4 is referenced for 3GPP2/CDMA interworking scenarios and influenced the design of GTP-based mobility. The Foreign Agent (FA) concept maps conceptually to the SGW.

2. MIPv4 Architecture

▶
  • Home Address: Permanent IP address on the home network — stays same across moves
  • Care-of Address (CoA): Temporary address on the visited network
  • Home Agent (HA): Router on home network that tunnels packets to MN's CoA
  • Foreign Agent (FA): Router on visited network that decapsulates tunneled packets
  • Registration: MN registers CoA with HA via Registration Request/Reply
  Correspondent          Home Agent (HA)          Foreign Agent (FA)
Node (CN)             Home Network              Visited Network
|                      |                          |
|  Packets to MN's     |                          |
|  Home Address        |                          |
|--------------------->|                          |
|                      |  IP-in-IP Tunnel         |
|                      |  (Home Addr → CoA)       |
|                      |------------------------->|
|                      |                          |
|                      |                     MN <--+
|                      |                     (detunneled)
|                      |                          |
|  Reverse Tunnel (optional)                      |
|<-------------------------------------------------|

3. Security Considerations

▶
  • Registration messages use HMAC-MD5 authentication (MN-HA, MN-FA, FA-HA extensions)
  • MD5 is cryptographically weak — modern deployments should use IPsec or stronger auth
  • Triangle routing (CN→HA→MN) is suboptimal — Route Optimization can improve but adds complexity
  • IP-in-IP tunnels without ESP provide no confidentiality — sensitive traffic needs encryption