Network Working Group A. Conta
Request for Comments: 2473 Lucent Technologies Inc.
Category: Standards Track S. Deering
Cisco Systems
December 1998
Generic Packet Tunneling in IPv6
Specification
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 (1998). All Rights Reserved.
Abstract
This document defines the model and generic mechanisms for IPv6
encapsulation of Internet packets, such as IPv6 and IPv4. The model
and mechanisms can be applied to other protocol packets as well, such
as AppleTalk, IPX, CLNP, or others.
Table of Contents
1. Introduction..................................................2
2. Terminology...................................................2
3. IPv6 Tunneling................................................4
3.1 IPv6 Encapsulation.......................................6
3.2 IPv6 Packet Processing in Tunnels........................7
3.3 IPv6 Decapsulation.......................................7
3.4 IPv6 Tunnel Protocol Engine..............................8
4. Nested Encapsulation.........................................11
4.1 Limiting Nested Encapsulation..........................12
4.1.1 Tunnel Encapsulation Limit Option................13
4.1.2 Loopback Encapsulation...........................15
4.1.3 Routing Loop Nested Encapsulation................15
5. Tunnel IPv6 Header...........................................16
5.1 Tunnel IPv6 Extension Headers...........................17
6. IPv6 Tunnel State Variables..................................19
6.1 IPv6 Tunnel Entry-Point Node............................19
6.2 IPv6 Tunnel Exit-Point Node.............................19
Conta & Deering Standards Track [Page 1]
RFC 2473 Generic Packet Tunneling in IPv6 December 1998
6.3 IPv6 Tunnel Hop Limit...................................19
6.4 IPv6 Tunnel Packet Traffic Class........................20
6.5 IPv6 Tunnel Flow Label..................................20
6.6 IPv6 Tunnel Encapsulation Limit.........................20
6.7 IPv6 Tunnel MTU.........................................20
7. IPv6 Tunnel Packet Size Issues...............................21
7.1 IPv6 Tunnel Packet Fragmentation........................21
7.2 IPv4 Tunnel Packet Fragmentation........................22
8. IPv6 Tunnel Error Reporting and Processing...................22
8.1 Tunnel ICMP Messages....................................27
8.2 ICMP Messages for IPv6 Original Packets.................28
8.3 ICMP Messages for IPv4 Original Packets.................29
8.4 ICMP Messages for Nested Tunnel Packets.................30
9. Security Considerations......................................30
10. Acknowledgments.............................................31
11. References..................................................31
Authors' Addresses..............................................32
Appendix A. Risk Factors in Recursive Encapsulation.............33
Full Copyright Statement........................................36
1. Introduction
This document specifies a method and generic mechanisms by which a
packet is encapsulated and carried as payload within an IPv6 packet.
The resulting packet is called an IPv6 tunnel packet. The forwarding
path between the source and destination of the tunnel packet is
called an IPv6 tunnel. The technique is called IPv6 tunneling.
A typical scenario for IPv6 tunneling is the case in which an
intermediate node exerts explicit routing control by specifying
particular forwarding paths for selected packets. This control is
achieved by prepending IPv6 headers to each of the selected original
packets. These prepended headers identify the forwarding paths.
In addition to the description of generic IPv6 tunneling mechanisms,
which is the focus of this document, specific mechanisms for
tunneling IPv6 and IPv4 packets are also described herein.
The keywords MUST, MUST NOT, MAY, OPTIONAL, REQUIRED, RECOMMENDED,
datatracker.ietf.org