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Generic Packet Tunneling in IPv6 Specification
RFC 2473

Document type: RFC - Proposed Standard (December 1998; No errata)
Document stream: IETF
Last updated: 2013-03-02
Other versions: plain text, pdf, html

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IESG State: RFC 2473 (Proposed Standard)
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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,

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