Network Working Group H. Levkowetz
Request for Comments: 3519 ipUnplugged
Category: Standards Track S. Vaarala
Netseal
April 2003
Mobile IP Traversal of Network Address Translation (NAT) Devices
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
Mobile IP's datagram tunnelling is incompatible with Network Address
Translation (NAT). This document presents extensions to the Mobile
IP protocol and a tunnelling method which permits mobile nodes using
Mobile IP to operate in private address networks which are separated
from the public internet by NAT devices. The NAT traversal is based
on using the Mobile IP Home Agent UDP port for encapsulated data
traffic.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Problem description . . . . . . . . . . . . . . . . . . 3
1.3 Assumptions . . . . . . . . . . . . . . . . . . . . . . 4
2. NAT Traversal Overview. . . . . . . . . . . . . . . . . . . . 5
2.1 Basic Message Sequence. . . . . . . . . . . . . . . . . 5
3. New Message Formats . . . . . . . . . . . . . . . . . . . . . 6
3.1 UDP Tunnel Request Extension. . . . . . . . . . . . . . 6
3.1.1 F (Force) Flag. . . . . . . . . . . . . . . . . . 7
3.1.2 R (Registration through FA Required) flag . . . . 8
3.1.3 Reserved Fields . . . . . . . . . . . . . . . . . 8
3.1.4 Encapsulation . . . . . . . . . . . . . . . . . . 8
3.1.5 Mobile IP Registration Bits . . . . . . . . . . . 9
3.2 UDP Tunnel Reply Extension. . . . . . . . . . . . . . . 9
3.2.1 Reply Code. . . . . . . . . . . . . . . . . . . . 10
Levkowetz & Vaarala Standards Track