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An IPv6-to-IPv4 Transport Relay Translator (RFC3142) Disclosure Number: IPCOM000005326D
Original Publication Date: 2001-Jun-01
Included in the Prior Art Database: 2019-Feb-13
Document File: 11 page(s) / 14K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

J. Hagino: AUTHOR [+1]

Related Documents

10.17487/RFC3142: DOI


The document describes an IPv6-to-IPv4 transport relay translator (TRT). This memo provides information for the Internet community.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 17% of the total text.

Network Working Group J. Hagino Request for Comments: 3142 K. Yamamoto Category: Informational IIJ Research Laboratory June 2001

An IPv6-to-IPv4 Transport Relay Translator

Status of this Memo

This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (2001). All Rights Reserved.


The document describes an IPv6-to-IPv4 transport relay translator (TRT). It enables IPv6-only hosts to exchange {TCP,UDP} traffic with IPv4-only hosts. A TRT system, which locates in the middle, translates {TCP,UDP}/IPv6 to {TCP,UDP}/IPv4, or vice versa.

The memo talks about how to implement a TRT system using existing technologies. It does not define any new protocols.

1. Problem domain

When you deploy an IPv6-only network, you still want to gain access to IPv4-only network resources outside, such as IPv4-only web servers. To solve this problem, many IPv6-to-IPv4 translation technologies are proposed, mainly in the IETF ngtrans working group. The memo describes a translator based on the transport relay technique to solve the same problem.

In this memo, we call this kind of translator "TRT" (transport relay translator). A TRT system locates between IPv6-only hosts and IPv4 hosts and translates {TCP,UDP}/IPv6 to {TCP,UDP}/IPv4, vice versa.

Advantages of TRT are as follows:

o TRT is designed to require no extra modification on IPv6-only initiating hosts, nor that on IPv4-only destination hosts. Some other translation mechanisms need extra modifications on IPv6-only initiating hosts, limiting possibility of deployment.

Hagino & Yamamoto Informational [Page 1]

RFC 3142 IPv6-to-IPv4 Transport Relay Translator June 2001

o The IPv6-to-IPv4 header converters have to take care of path MTU and fragmentation issues. However, TRT is free from this problem.

Disadvantages of TRT are as follows:

o TRT supports bidirectional traffic only. The IPv6-to-IPv4 header converters may be able to support other cases, such as unidirectional multicast datagrams.

o TRT needs a stateful TRT system between the communicating peers, just like NAT systems. While it is possible to place multiple TRT systems in a site (see Appendix A), a transport layer connection goes through particular, a single TRT system. The TRT system thus can be considered a single point of failure, again like NAT systems. Some other mechanisms, such as SIIT [Nordmark, 2000], use stateless translator systems which can avoid a single point of failure.

o Special code is necessary to relay NAT-unfriendly protocols. Some of NAT-unfriendly protocols, including IPsec, cannot be used across TRT system.

This memo assumes that traffic is initiated by an IPv6-only host destined to an IPv4-only host. The memo can be extended to handle opposite direction, if an appropriate address mapping mechanism is introduced.

2. IPv4-to-IPv4 transport relay

To help understanding of the proposal in the...