RFC 3022 (rfc3022) - Page 1 of 16

Traditional IP Network Address Translator (Traditional NAT)

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Network Working Group                                       P. Srisuresh
Request for Comments: 3022                              Jasmine Networks
Obsoletes: 1631                                               K. Egevang
Category: Informational                                Intel Corporation
                                                            January 2001


      Traditional IP Network Address Translator (Traditional NAT)

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.

Preface

   The NAT operation described in this document extends address
   translation introduced in RFC 1631 and includes a new type of network
   address and TCP/UDP port translation.  In addition, this document
   corrects the Checksum adjustment algorithm published in RFC 1631 and
   attempts to discuss NAT operation and limitations in detail.

Abstract

   Basic Network Address Translation or Basic NAT is a method by which
   IP addresses are mapped from one group to another, transparent to end
   users.  Network Address Port Translation, or NAPT is a method by
   which many network addresses and their TCP/UDP (Transmission Control
   Protocol/User Datagram Protocol) ports are translated into a single
   network address and its TCP/UDP ports.  Together, these two
   operations, referred to as traditional NAT, provide a mechanism to
   connect a realm with private addresses to an external realm with
   globally unique registered addresses.

1. Introduction

   The need for IP Address translation arises when a network's internal
   IP addresses cannot be used outside the network either for privacy
   reasons or because they are invalid for use outside the network.

   Network topology outside a local domain can change in many ways.
   Customers may change providers, company backbones may be reorganized,
   or providers may merge or split.  Whenever external topology changes



Srisuresh & Egevang          Informational
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