RFC 3235 (rfc3235) - Page 1 of 13

Network Address Translator (NAT)-Friendly Application Design Guidelines

Alternative Format: Original Text Document
Next >
Network Working Group                                           D. Senie
Request for Comments: 3235                        Amaranth Networks Inc.
Category: Informational                                     January 2002


               Network Address Translator (NAT)-Friendly
                     Application Design Guidelines

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

   This document discusses those things that application designers might
   wish to consider when designing new protocols.  While many common
   Internet applications will operate cleanly in the presence of Network
   Address Translators, others suffer from a variety of problems when
   crossing these devices.  Guidelines are presented herein to help
   ensure new protocols and applications will, to the extent possible,
   be compatible with NAT (Network Address Translation).

1. Introduction

   Other documents that describe Network Address Translation (NAT)
   discuss the Terminology and Considerations [RFC 2663] and Protocol
   Issues [RFC 3022], [RFC 3027] or discuss the implications of NAT
   [RFC 2993].  All of those relate to various issues with the NAT
   mechanism, effects on protocols and effects upon general Internet
   architecture.

   It is the focus of this document to provide recommendations to
   authors of new protocols about the effects to consider when designing
   new protocols such that special handling is not required at NAT
   gateway points.

   When a protocol is unable to pass cleanly through a NAT, the use of
   an Application Level Gateway (ALG) may still permit operation of the
   protocol.  Depending on the encoding used in a protocol, an ALG may
   be difficult or easy to construct, though in some cases it may not be
   possible at all.  While adjunct to NAT, the formulation of protocols
   that cannot directly operate through NAT should be considered such



Senie                        Informational
Next >