RFC 6275

Mobility Support in IPv6
Standards Track Obsoletes: RFC 3775
July 2011
RFC Library > IP Mobility > RFC 6275
Abstract: Mobile IPv6 (MIPv6) enables IPv6 nodes to remain reachable while moving between networks, maintaining transport and application-layer connections. MIPv6 concepts underpin 3GPP's Dual-Stack Mobile IPv6 (DSMIPv6) for non-3GPP access mobility.
Canonical source: https://www.rfc-editor.org/rfc/rfc6275  |  IETF Datatracker

1. Introduction

▶

MIPv6 is the IPv6 counterpart of Mobile IPv4, with significant improvements including route optimization as a built-in feature, elimination of foreign agents, and integration with IPv6 Neighbor Discovery.

In 3GPP, MIPv6 was extended to DSMIPv6 (Dual-Stack MIPv6, RFC 5555) for UE mobility across 3GPP and non-3GPP accesses. DSMIPv6 operates on the S2c interface between UE and PGW, allowing the UE to maintain its PDN connection when moving between LTE, Wi-Fi, and other access technologies.

2. MIPv6 Signaling

▶
Message Description
Binding Update (BU) Mobile node registers CoA with Home Agent
Binding Acknowledgment (BA) Home Agent confirms binding registration
Home Test Init (HoTI) Initiate return routability with CN (via HA)
Care-of Test Init (CoTI) Initiate return routability with CN (direct)
Home Test (HoT) CN nonce for return routability (via HA)
Care-of Test (CoT) CN nonce for return routability (direct)
Binding Refresh Request (BRR) CN requests updated binding

3. MIPv6 Operation

▶

Route optimization allows the MN to communicate directly with CNs without traversing the HA, reducing latency. The return routability procedure provides lightweight authorization for route-optimized bindings.

  MN (UE)           Home Agent (PGW)         Correspondent Node
|                     |                        |
|  Binding Update     |                        |
|  [HoA, CoA, Seq#,   |                        |
|   Lifetime, Auth]   |                        |
|-------------------->|                        |
|                     |                        |
|  Binding Ack        |                        |
|  [Status, Lifetime] |                        |
|<--------------------|                        |
|                     |                        |
|  HA intercepts packets for HoA               |
|  and tunnels to CoA                           |
|                     |                        |
|  === Route Optimization (optional) ===        |
|                     |                        |
|  HoTI (via HA)----->|  HoTI----------------->|
|  CoTI (direct)------|------------------------>|
|                     |  HoT<------------------|
|  HoT<--------------|                         |
|  CoT<-----------------------------------------|
|                     |                        |
|  BU (to CN, with    |                        |
|   keygen token)     |                        |
|------------------------------------------>   |
|                     |                        |
|  Direct data path (optimized)                |
|<===========================================> |

4. 3GPP DSMIPv6 Usage

▶
  • S2c interface: DSMIPv6 between UE and PGW for inter-access mobility
  • IKEv2 + IPsec: DSMIPv6 uses IPsec for BU/BA protection (vs. return routability for CN)
  • Dual-stack: Handles both IPv4 and IPv6 home addresses over IPv6 tunnel
  • Inter-access handover: UE moves from LTE to Wi-Fi — sends BU with new CoA, PGW updates binding
  • Largely replaced: 5G uses N3IWF/TNGF instead of DSMIPv6 for non-3GPP access

5. Security Considerations

▶
  • BU/BA between MN and HA MUST be protected by IPsec ESP — contains binding state
  • Route optimization uses return routability procedure — lighter security, vulnerable to on-path attackers
  • Binding Update without proper authorization could redirect traffic (hijack flows)
  • IPsec SA lifetime should align with binding lifetime to avoid security gaps