Network Address Translation - Protocol Translation (NAT-PT)
RFC 2766

 
Document Type RFC - Historic (February 2000; No errata)
Obsoleted by RFC 4966
Updated by RFC 3152
Last updated 2013-03-02
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IESG IESG state RFC 2766 (Historic)
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Network Working Group                                         G. Tsirtsis
Request for Comments: 2766                                             BT
Category: Standards Track                                    P. Srisuresh
                                                    Campio Communications
                                                            February 2000

      Network Address Translation - Protocol Translation (NAT-PT)

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 (2000).  All Rights Reserved.

Abstract

   This document specifies an IPv4-to-IPv6 transition mechanism, in
   addition to those already specified in [TRANS]. This solution
   attempts to provide transparent routing, as defined in [NAT-TERM], to
   end-nodes in V6 realm trying to communicate with end-nodes in V4
   realm and vice versa. This is achieved using a combination of Network
   Address Translation and Protocol Translation. The scheme described
   does not mandate dual-stacks (i.e., IPv4 as well as V6 protocol
   support) or special purpose routing requirements (such as requiring
   tunneling support) on end nodes. This scheme is based on a
   combination of address translation theme as described in [NAT-TERM]
   and V6/V4 protocol translation theme as described in [SIIT].

Acknowledgements

   Special thanks to Pedro Marques for reviewing an earlier version of
   this memo.  Also, many thanks to Alan O'Neill and Martin Tatham, as
   the mechanism described in this document was initially developed
   through discussions with them.

Tsirtsis & Srisuresh        Standards Track                     [Page 1]
RFC 2766                         NAT-PT                    February 2000

Table of Contents

   1. Introduction..................................................  2
   2. Terminology...................................................  3
      2.1 Network Address Translation (NAT).........................  4
      2.2 NAT-PT flavors............................................  4
         2.2.1 Traditional-NAT-PT...................................  4
         2.2.2 Bi-directional-NAT-PT................................  5
      2.3 Protocol Translation (PT).................................  5
      2.4 Application Level Gateway (ALG)...........................  5
      2.5 Requirements..............................................  5
   3. Traditional-NAT-PT operation (V6 to V4).......................  6
      3.1 NAT-PT Outgoing Sessions..................................  6
      3.2 NAPT-PT Outgoing Sessions.................................  7
   4. Use of DNS-ALG for Address assignment.........................  8
      4.1 V4 Address Assignment for Incoming Connections (V4 to V6).  9
      4.2 V4 Address Assignment for Outgoing Connections (V6 to V4). 11
   5. Protocol Translation Details.................................. 12
      5.1 Translating IPv4 Headers to IPv6 Headers.................. 13
      5.2 Translating IPv6 Headers to IPv4 Headers.................. 13
      5.3 TCP/UDP/ICMP Checksum Update.............................. 13
   6. FTP Application Level Gateway (FTP-ALG) Support............... 14
      6.1 Payload modifications for V4 originated FTP sessions...... 15
      6.2 Payload modifications for V6 originated FTP sessions...... 16
      6.3 Header updates for FTP control packets.................... 16
   7. NAT-PT Limitations and Future Work............................ 17
      7.1 Topology Limitations...................................... 17
      7.2 Protocol Translation Limitations.......................... 17
      7.3 Impact of Address Translation............................. 18
      7.4 Lack of End-to-End Security............................... 18
      7.5 DNS Translation and DNSSEC................................ 18
   8. Applicability Statement....................................... 18
   9. Security Considerations....................................... 19
   10. References................................................... 19
   Authors' Addresses............................................... 20
   Full Copyright Statement......................................... 21

1. Introduction

   IPv6 is a new version of the IP protocol designed to modernize IPv4
   which was designed in the 1970s. IPv6 has a number of advantages over
   IPv4 that will allow for future Internet growth and will simplify IP
   configuration and administration. IPv6 has a larger address space
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