IPv6 translation mechanisms

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IPv6 translation mechanisms are used to allow IPv6-connected hosts to access IPv4-connected hosts.

IPv6 translation mechanisms were first defined in RFC 1933 but this RFC has been obsoleted by RFC 4213.

RFC 2765 defines a mechanism known as Stateless IP/ICMP Translation, or SIIT

RFC 3142 defines the TRT method, or Transport Relay Translation. This is the most common NAT-PT implementation for IPv6 transition.

Contents

[edit] SIIT

In computer networking, Stateless IP/ICMP Translation is a mechanism which translates IPv6 packets into IPv4 packets and vice-versa.

It was initially drafted in February of 2000 by E. Nordmark of Sun Microsystems and is described in RFC 2765 (Network Working Group at Internet Engineering Task Force).

Basically SIIT describes a method by which a router interprets an IPv4 header and creates a parallel IPv6 header with equivalent information and the inverse equivalent operation of converting an IPv6 header into an IPv4 header. The actual means of converting an IPv4 address to an IPv6 address or vice-versa may vary, and the means by which the routing occurs is described as unspecified in the RFC.

Due to the method in which SIIT operates it is not a sufficient migration mechanism in that it is incapable of coordinating more than two unique addresses on either side. This means that every IPv6 host would be required to have a globally routable IPv4 address as well.

[edit] NAT-PT

Network Address Translation/Protocol Translation (or simply NAT-PT) is defined in RFC 2766 but due to numerous problems, it has been obsoleted by RFC 4966 and made historic.. It is typically used in conjunction with a DNS Application-level gateway (DNS-ALG) implementation.

[edit] NAPT-PT

While almost identical to NAT-PT, Network Address Port Translation + Protocol Translation which is also described in RFC 2766 adds translation of the ports as well as the address. This is done primarily to avoid two hosts on one side of the mechanism from using the same exposed port on the other side of the mechanism, which could cause application instability and/or security flaws.

[edit] TRT

TRT, or Transport Relay Translation, was defined in RFC 3142. This is the most common form of NAT-PT/NAPT-PT but relies on DNS translation between AAAA and A records known as DNS-ALG as defined in RFC 2694.


[edit] Translation Mechanisms

[edit] NAT-PT Implementations

[edit] TRT Implementations

  • faithd: BSD-based static TRT implementation
  • pTRTd: Attempt at TRT for Linux.
  • STRATA: Commercial TRT/NAPT-PT routers.
  • Click NATPT: Implementation for The Click Modular Router Project

[edit] DNS-ALG Implementations

  • totd: 'Trick or Treat Daemon' DNS translator for BSD & Linux
  • ATX: Ambriel Technologies implements NATPT and a DNS-ALG

[edit] Other Mechanisms

[edit] See also

[edit] External websites

[edit] References

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