RFC 2893 (rfc2893) - Page 2 of 29


Transition Mechanisms for IPv6 Hosts and Routers



Alternative Format: Original Text Document



RFC 2893               IPv6 Transition Mechanisms            August 2000


Table of Contents

   1.  Introduction.............................................    2
      1.1.  Terminology.........................................    3
      1.2.  Structure of this Document..........................    5
   2.  Dual IP Layer Operation..................................    6
      2.1.  Address Configuration...............................    7
      2.2.  DNS.................................................    7
      2.3.  Advertising Addresses in the DNS....................    8
   3.  Common Tunneling Mechanisms..............................    9
      3.1.  Encapsulation.......................................   11
      3.2.  Tunnel MTU and Fragmentation........................   11
      3.3.  Hop Limit...........................................   13
      3.4.  Handling IPv4 ICMP errors...........................   13
      3.5.  IPv4 Header Construction............................   15
      3.6.  Decapsulation.......................................   16
      3.7.  Link-Local Addresses................................   17
      3.8.  Neighbor Discovery over Tunnels.....................   18
   4.  Configured Tunneling.....................................   18
      4.1.  Default Configured Tunnel...........................   19
      4.2.  Default Configured Tunnel using IPv4 "Anycast Address" 19
      4.3.  Ingress Filtering...................................   20
   5.  Automatic Tunneling......................................   20
      5.1.  IPv4-Compatible Address Format......................   20
      5.2.  IPv4-Compatible Address Configuration...............   21
      5.3.  Automatic Tunneling Operation.......................   22
      5.4.  Use With Default Configured Tunnels.................   22
      5.5.  Source Address Selection............................   23
      5.6.  Ingress Filtering...................................   23
   6.  Acknowledgments..........................................   24
   7.  Security Considerations..................................   24
   8.  Authors' Addresses.......................................   24
   9.  References...............................................   25
   10.  Changes from RFC 1933...................................   26
   11.  Full Copyright Statement................................   29

1.  Introduction

   The key to a successful IPv6 transition is compatibility with the
   large installed base of IPv4 hosts and routers.  Maintaining
   compatibility with IPv4 while deploying IPv6 will streamline the task
   of transitioning the Internet to IPv6.  This specification defines a
   set of mechanisms that IPv6 hosts and routers may implement in order
   to be compatible with IPv4 hosts and routers.

   The mechanisms in this document are designed to be employed by IPv6
   hosts and routers that need to interoperate with IPv4 hosts and
   utilize IPv4 routing infrastructures.  We expect that most nodes in



Gilligan & Nordmark         Standards Track