RFC 3424 (rfc3424) - Page 1 of 9
IAB Considerations for UNilateral Self-Address Fixing (UNSAF) Across Network Address Translation
Alternative Format: Original Text Document
Network Working Group L. Daigle, Ed.
Request for Comments: 3424 Internet Architecture Board
Category: Informational IAB
November 2002
IAB Considerations for UNilateral Self-Address Fixing (UNSAF)
Across Network Address Translation
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 (2002). All Rights Reserved.
Abstract
As a result of the nature of Network Address Translation (NAT)
Middleboxes, communicating endpoints that are separated by one or
more NATs do not know how to refer to themselves using addresses that
are valid in the addressing realms of their (current and future)
peers. Various proposals have been made for "UNilateral Self-Address
Fixing (UNSAF)" processes. These are processes whereby some
originating endpoint attempts to determine or fix the address (and
port) by which it is known to another endpoint - e.g. to be able to
use address data in the protocol exchange, or to advertise a public
address from which it will receive connections.
This document outlines the reasons for which these proposals can be
considered at best as short term fixes to specific problems and the
specific issues to be carefully evaluated before creating an UNSAF
proposal.
1. Introduction
As a result of the nature of Network Address (and port) Translation
(NAT) Middleboxes, communicating endpoints that are separated by one
or more NATs do not know how to refer to themselves using addresses
that are valid in the addressing realms of their (current and future)
peers - the address translation is locked within the NAT box. For
some purposes, endpoints need to know the addresses (and/or ports) by
which they are known to their peers. There are two cases: 1) when
the client initiates communication, starting the communication has
the side effect of creating an address binding in the NAT device and
Daigle & IAB Informational
