Problem Statement: Dual Stack Mobility
RFC 4977

Network Working Group                                        G. Tsirtsis
Request for Comments: 4977                                      Qualcomm
Category: Informational                                       H. Soliman
                                                    Elevate Technologies
                                                             August 2007

                 Problem Statement: Dual Stack Mobility

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Abstract

   This document discusses the issues associated with mobility
   management for dual stack mobile nodes.  Currently, two mobility
   management protocols are defined for IPv4 and IPv6.  Deploying both
   in a dual stack mobile node introduces a number of problems.
   Deployment and operational issues motivate the use of a single
   mobility management protocol.  This document discusses such
   motivations.  The document also discusses requirements for the Mobile
   IPv4 (MIPv4) and Mobile IPv6 (MIPv6) protocol so that they can
   support mobility management for a dual stack node.

Table of Contents

   1.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 2
   2.  Introduction and Motivation . . . . . . . . . . . . . . . . . . 2
   3.  Problem Description . . . . . . . . . . . . . . . . . . . . . . 3
     3.1.  The Impossibility of Maintaining IP Connectivity  . . . . . 4
     3.2.  Implementation Burdens  . . . . . . . . . . . . . . . . . . 4
     3.3.  Operational Burdens . . . . . . . . . . . . . . . . . . . . 4
     3.4.  Mobility Management Inefficiencies  . . . . . . . . . . . . 4
     3.5.  IPv4 to IPv6 Transition Mechanisms  . . . . . . . . . . . . 5
   4.  Conclusions and Recommendations . . . . . . . . . . . . . . . . 5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     6.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     6.2.  Informative References  . . . . . . . . . . . . . . . . . . 6

Tsirtsis & Soliman           Informational                      [Page 1]
RFC 4977         Problem Statement: Dual Stack Mobility      August 2007

1.  Terminology

   This document uses the following terms as defined in Stateless IP/
   ICMP Translation (SIIT) [RFC2765]: IPv4-capable node, IPv4-enabled
   node, IPv6-capable node, IPv6-enabled node.

   The following terms are introduced in this document:

   - MIPv4-capable node:

      A node that supports MIPv4 [RFC3344] in its implementation.  This
      allows the mobile node to configure a home address (statically or
      dynamically) and use such address in its Mobile IPv4 signaling.  A
      MIPv4-capable node may also be IPv6-capable or IPv6-enabled and
      must be IPv4-capable.

   - MIPv6-capable node:

      A node that supports MIPv6 [RFC3775] by configuring a home address
      and using such address in its Mobile IPv6 signaling.  A MIPv6-
      enabled node may also be IPv4-capable or IPv4-enabled and must be
      IPv6-capable.

2.  Introduction and Motivation

   A MIPv4-capable node can use Mobile IPv4 [RFC3344] to maintain
   connectivity while moving between IPv4 subnets.  Similarly, a MIPv6-
   capable node can use Mobile IPv6 [RFC3775] to maintain connectivity
   while moving between IPv6 subnets.

   One of the ways of migrating to IPv6 is to deploy nodes that are both
   IPv4 and IPv6 capable.  Such nodes will be able to get both IPv4 and
   IPv6 addresses and thus can communicate with the current IPv4
   Internet as well as any IPv6 nodes and networks as they become
   available.

   A node that is both IPv4 and IPv6 capable can use Mobile IPv4 for its
   IPv4 stack and Mobile IPv6 for its IPv6 stack so that it can move
   between IPv4 and IPv6 subnets.  While this is possible, it does not
   ensure connectivity since that also depends on the IP version support
   of the network accessed.  Supporting Mobile IPv4 and Mobile IPv6 is
   also more inefficient since it requires:

Tsirtsis & Soliman           Informational                      [Page 2]
RFC 4977         Problem Statement: Dual Stack Mobility      August 2007

   -  Mobile nodes to be both MIPv4 and MIPv6 capable.

   -  Mobile nodes to send two sets of signaling messages on every
      handoff.

   -  Network Administrators to run and maintain two sets of mobility
      management systems on the same network, with each of these systems
      requiring its own set of optimizations.

   This document discusses the potential inefficiencies, IP connectivity
   problems, and operational issues that are evident when running both