RFC 2473 (rfc2473) - Page 2 of 36

Generic Packet Tunneling in IPv6 Specification

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,
   SHALL, SHALL NOT, SHOULD, SHOULD NOT are to be interpreted as defined
   in RFC 2119.

2. Terminology

   original packet

        a packet that undergoes encapsulation.




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