Teredo: Tunneling IPv6 over UDP through Network Address Translations (NATs)
RFC 4380

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Network Working Group                                         C. Huitema
Request for Comments: 4380                                     Microsoft
Category: Standards Track                                  February 2006

                    Teredo: Tunneling IPv6 over UDP
              through Network Address Translations (NATs)

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 (2006).

Abstract

   We propose here a service that enables nodes located behind one or
   more IPv4 Network Address Translations (NATs) to obtain IPv6
   connectivity by tunneling packets over UDP; we call this the Teredo
   service.  Running the service requires the help of "Teredo servers"
   and "Teredo relays".  The Teredo servers are stateless, and only have
   to manage a small fraction of the traffic between Teredo clients; the
   Teredo relays act as IPv6 routers between the Teredo service and the
   "native" IPv6 Internet.  The relays can also provide interoperability
   with hosts using other transition mechanisms such as "6to4".

Table of Contents

   1. Introduction ....................................................3
   2. Definitions .....................................................4
      2.1. Teredo Service .............................................4
      2.2. Teredo Client ..............................................4
      2.3. Teredo Server ..............................................4
      2.4. Teredo Relay ...............................................4
      2.5. Teredo IPv6 Service Prefix .................................4
      2.6. Global Teredo IPv6 Service Prefix ..........................4
      2.7. Teredo UDP Port ............................................4
      2.8. Teredo Bubble ..............................................4
      2.9. Teredo Service Port ........................................5
      2.10. Teredo Server Address .....................................5
      2.11. Teredo Mapped Address and Teredo Mapped Port ..............5
      2.12. Teredo IPv6 Client Prefix .................................5

Huitema                     Standards Track                     [Page 1]
RFC 4380                         Teredo                    February 2006

      2.13. Teredo Node Identifier ....................................5
      2.14. Teredo IPv6 Address .......................................5
      2.15. Teredo Refresh Interval ...................................5
      2.16. Teredo Secondary Port .....................................6
      2.17. Teredo IPv4 Discovery Address .............................6
   3. Design Goals, Requirements, and Model of Operation ..............6
      3.1. Hypotheses about NAT Behavior ..............................6
      3.2. IPv6 Provider of Last Resort ...............................8
      3.3. Operational Requirements ...................................9
      3.4. Model of Operation ........................................10
   4. Teredo Addresses ...............................................11
   5. Specification of Clients, Servers, and Relays ..................13
      5.1. Message Formats ...........................................13
      5.2. Teredo Client Specification ...............................16
      5.3. Teredo Server Specification ...............................31
      5.4. Teredo Relay Specification ................................33
      5.5. Implementation of Automatic Sunset ........................36
   6. Further Study, Use of Teredo to Implement a Tunnel Service .....37
   7. Security Considerations ........................................38
      7.1. Opening a Hole in the NAT .................................38
      7.2. Using the Teredo Service for a Man-in-the-Middle Attack ...39
      7.3. Denial of the Teredo service ..............................42
      7.4. Denial of Service against Non-Teredo Nodes ................43
   8. IAB Considerations .............................................46
      8.1. Problem Definition ........................................46
      8.2. Exit Strategy .............................................47
      8.3. Brittleness Introduced by Teredo ..........................48
      8.4. Requirements for a Long-Term Solution .....................50
   9. IANA Considerations ............................................50
   10. Acknowledgements ..............................................50
   11. References ....................................................51
      11.1. Normative References .....................................51
      11.2. Informative References ...................................52