RFC 4977

Problem Statement: Dual Stack Mobility

📅 published August 2007, from ietf

RFC 4977: Problem Statement: Dual Stack Mobility 🦋

RFC number: 4977 💖
Title: Problem Statement: Dual Stack Mobility
Authors: G. Tsirtsis (Qualcomm) and H. Soliman (Elevate Technologies) 👑
Category: Informational (it's info only, not a spec 🙈)
Date: August 2007
Stream: Network Working Group
Obsoletes / Updates: the title block lists neither, so this doc doesn't replace or update any other RFC ✨

Status of This Memo 📜

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

Abstract 🎀

Okay so this doc is all about mobility management for dual stack mobile nodes (devices that run both IPv4 and IPv6 at the same time 📱). Right now there are two mobility management protocols, one for IPv4 and one for IPv6. Running both on a dual stack device causes a bunch of problems 😭. Deployment and operations issues are why people want a single mobility management protocol instead, and the doc explains those reasons. It also covers what Mobile IPv4 (MIPv4) and Mobile IPv6 (MIPv6) would need so they can handle mobility for a dual stack node. Bestie, it's giving "fix the root cause" energy 💅.

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

1. Terminology 🧚

This doc uses the terms IPv4-capable node, IPv4-enabled node, IPv6-capable node, and IPv6-enabled node, all defined in Stateless IP/ICMP Translation (SIIT) [RFC2765]. 💜

These new terms are introduced in this document:

MIPv4-capable node:

A node that supports MIPv4 [RFC3344] in its implementation. This lets the mobile node set up a home address (statically or dynamically) and use that address in its Mobile IPv4 signaling. A MIPv4-capable node may also be IPv6-capable or IPv6-enabled, and it must be IPv4-capable. 🌸

MIPv6-capable node:

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

2. Introduction and Motivation 🌷

A MIPv4-capable node can use Mobile IPv4 [RFC3344] to stay connected while it moves between IPv4 subnets. Same vibe for a MIPv6-capable node: it can use Mobile IPv6 [RFC3775] to stay connected while it moves between IPv6 subnets. 🫶

One way to migrate to IPv6 is to deploy nodes that are both IPv4 and IPv6 capable. These nodes can get both IPv4 and IPv6 addresses, so they can talk to the current IPv4 Internet and also to any IPv6 nodes and networks as they show up. ✨

A node that is both IPv4 and IPv6 capable could use Mobile IPv4 for its IPv4 stack and Mobile IPv6 for its IPv6 stack, so it can move between IPv4 and IPv6 subnets. That's possible, but it doesn't guarantee connectivity, since that also depends on which IP version the accessed network supports. Running both Mobile IPv4 and Mobile IPv6 is also less efficient, because it requires:

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 system needing its own set of optimizations.

This doc looks at the inefficiencies, IP connectivity problems, and operational issues that show up when both mobility management protocols run at the same time. It also proposes a work area for the IETF to take up on this topic and discusses requirements for good solutions. 🔥

3. Problem Description 💅

Mobile IP (v4 and v6) uses a signaling protocol to set up tunnels between two endpoints. That's Registration requests in MIPv4 [RFC3344] and Binding updates in MIPv6 [RFC3775]. Right now, Mobile IP signaling is tightly coupled to the address family (IPv4 or IPv6) used in the connections it tries to manage, and there's no fundamental technical reason for that coupling. If Mobile IP were treated as a tunnel-setup protocol, it should be able to set up IP in IP tunnels no matter which IP version is used in the outer and inner headers. Other protocols, like SIP [RFC3261], can use either an IPv4- or IPv6-based signaling plane to manage IPv4 and IPv6 connections. 🧠

A node that is both MIPv4 and MIPv6 capable will need the following to roam within the Internet:

The network operator needs to make sure the home agent supports both protocols, or that it has two separate Home Agents supporting the two protocols, each with its own management. 😩
Double the configuration on the mobile node and the home agent (for example, security associations). 🙈
IP-layer local network optimizations for handovers will also need to be duplicated. 🍓

We argue that all of the above makes Mobile IPv6 harder to deploy, along with any dual stack solution in a mobile environment. We'll dig into some issues with the current approach in the sections below. 💖

3.1. The Impossibility of Maintaining IP Connectivity 🌈

Even if a mobile node is both MIPv4 and MIPv6 capable, connectivity across different networks isn't guaranteed. That depends on the IPv4/IPv6 capabilities of the networks the mobile node is visiting. For example, a node trying to connect through an IPv4-only network wouldn't be able to keep its IPv6 applications connected, and the reverse is also true. Honestly, this is potentially the most serious problem in this doc 😭.

3.2. Implementation Burdens 🛠️

As mentioned above, a node that is IPv4 and IPv6 capable must also be MIPv4 and MIPv6 capable to roam within the Internet. Being able to use both IP versions from one mobility protocol means you only need to implement that one protocol, as long as you know which protocol to pick. But when a mobile node has to work on any network, it may still need both protocols. 🦋

3.3. Operational Burdens 🍓

As we said earlier, deploying both protocols means managing both protocols on the mobile node and the home agent. That adds a lot of operational work for the network operator. The operator would need deep knowledge of both protocols, and that might be hard to justify when there aren't big gains. 🧐

Deploying both protocols also means duplicating security credentials on mobile nodes and home agents. That includes IPsec security associations, keying material, and new authentication protocols for Mobile IPv6, on top of the credentials and associations Mobile IPv4 already needs. Depending on the security mechanisms used, and with some further work, it might be possible to rely on one common set of credentials. But if nothing else changes, that duplication is still a big deal with no gain for the operator or the mobile node. 🔐

3.4. Mobility Management Inefficiencies 🌸

Say a mobile node is moving within a dual stack access network. Every time it moves, it has to send two Mobile IP messages to its home agent so its IPv4 and IPv6 connections survive. There's no good reason for that duplication. If local mobility optimizations were deployed (for example, Hierarchical Mobile IPv6 (HMIPv6) [RFC4140] or Fast handovers for Mobile IPv4 [RFC4068]), the mobile node would need to update the local agents running each protocol. Ironically, one local agent might run both HMIPv6 and a local MIPv4 home agent. 🙃 Clearly, it's not ideal to send two messages and finish two sets of transactions for the same basic optimization. 😤

So running Mobile IPv4 and Mobile IPv6 in parallel will make mobility management in the Internet more complicated, and it will use more bandwidth at the critical handover moment for no obvious gain. 💀

3.5. IPv4 to IPv6 Transition Mechanisms 🌈

The IETF has standardized several transition mechanisms so networks and end nodes can get IPv6 connectivity while the Internet moves from IPv4 to IPv6. Some of those transition mechanisms can be combined with Mobile IPv4 or Mobile IPv6, but none of the known mechanisms have been shown to help with the issues described in this document. Sadly, no main character solution here yet 😭🎀

To be continued in part 2 with Section 4 (Conclusions and Recommendations), Section 5 (Security Considerations), and Section 6 (References) ✨🦋

4. Conclusions and Recommendations ✨

okay so the big takeaway is that Mobile IPv4 and Mobile IPv6 are both super tangled up with the signaling and the IP addresses that upper layers use 🫣 that coupling is the root of basically everything we've been complaining about. 💜

Here's the situation, bestie 🌸 MIPv4 is already deployed everywhere, and MIPv6 is expected to show up. So we're gonna need a gradual move from IPv4 mobility management over to IPv6. Running both protocols at the same time is inefficient and comes with all the problems we already covered, so that's a no-go energy 💀 The gradual transition can happen whenever operators or implementers decide it's needed or appropriate. Until then, it's important to make sure those problems can be avoided. So this section lists some actions the IETF should take to fix the problems, without forcing anyone to run two mobility management protocols at once. ✨

The Mobile IPv6 Working Group landed on the view that, to allow a gradual transition based on current standards and deployment, these work areas would be reasonable 🎀

It should be possible to run one mobility management protocol that can manage mobility for both IPv4 and IPv6 addresses used by upper layers. Both Mobile IPv4 and Mobile IPv6 should be able to perform such tasks. It may not be possible to support route optimization for Mobile IPv6 in all cases 🥺 however, mobility management and session continuity can still be supported. 🦋
It should be possible to create IPv4 extensions to Mobile IPv6 so that an IPv4 and IPv6 capable mobile node can register its IPv4 and IPv6 home addresses to an IPv4- and IPv6-enabled Home Agent using MIPv6 signaling only. 💅
It should be possible to create IPv6 extensions to Mobile IPv4 so that an IPv4 and IPv6 capable mobile node can register its IPv4 and IPv6 home addresses to an IPv4- and IPv6-enabled Home Agent using Mobile IPv4 signaling only. 🧚
It should also be possible to extend MIPv4 [RFC3344] and MIPv6 [RFC3775] so that a mobile node can register a single care-of address (IPv4 or IPv6) to which IPv4 and/or IPv6 packets can be tunneled. 👑

If the IETF goes for all of these paths, a vendor could support one mobility management protocol and still dodge the incompatibility and inefficiency problems from this document. Operators could also decide to stick with one mobility management protocol the whole time IPv4 and IPv6 are coexisting 🌈 BUT, and this is a big but 😭, a mobile node would be forced to pick one approach or the other, or else install both and switch between them depending on the situation. 🍓

5. Security Considerations 🔒

This document is a problem statement that does not by itself introduce any security issues. 🫶

6. References 📚

6.1. Normative References

[RFC2765]  Nordmark, E., "Stateless IP/ICMP Translation Algorithm
           (SIIT)", RFC 2765, February 2000.

[RFC3344]  Perkins, C., "IP Mobility Support for IPv4", RFC 3344,
           August 2002.

[RFC3775]  Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
           in IPv6", RFC 3775, June 2004.

6.2. Informative References

[RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
           A., Peterson, J., Sparks, R., Handley, M., and E.
           Schooler, "SIP: Session Initiation Protocol", RFC 3261,
           June 2002.

[RFC4068]  Koodli, R., "Fast Handovers for Mobile IPv6", RFC 4068,
           July 2005.

[RFC4140]  Soliman, H., Castelluccia, C., El Malki, K., and L.
           Bellier, "Hierarchical Mobile IPv6 Mobility Management
           (HMIPv6)", RFC 4140, August 2005.

Authors' Addresses 🖊️

George Tsirtsis
Qualcomm

Phone: +908-443-8174
EMail: tsirtsis@qualcomm.com


Hesham Soliman
Elevate Technologies

Phone: +614-111-410-445
EMail: hesham@elevatemobile.com

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