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DNS extensions to Network Address Translators (DNS_ALG) (RFC2694)

IP.com Disclosure Number: IPCOM000003287D
Original Publication Date: 1999-Sep-01
Included in the Prior Art Database: 2000-Sep-13
Document File: 24 page(s) / 63K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

P. Srisuresh: AUTHOR [+4]

Abstract

Domain Name Service (DNS) provides name to address mapping within a routing class (ex: IP). Network Address Translators (NATs) attempt to provide transparent routing between hosts in disparate address realms of the same routing class. Typically, NATs exist at the border of a stub domain, hiding private addresses from external addresses. This document identifies the need for DNS extensions to NATs and outlines how a DNS Application Level Gateway (DNS_ALG) can meet the need. DNS_ALG modifies payload transparently to alter address mapping of hosts as DNS packets cross one address realm into another. The document also illustrates the operation of DNS_ALG with specific examples.

This text was extracted from a ASCII document.
This is the abbreviated version, containing approximately 4% of the total text.

Network Working Group P. Srisuresh

Request for Comments: 2694 Consultant

Category: Informational G. Tsirtsis

BT Laboratories

P. Akkiraju

Cisco Systems

A. Heffernan

Juniper Networks

September 1999

DNS extensions to Network Address Translators (DNS_ALG)

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 (1999). All Rights Reserved.

Abstract

Domain Name Service (DNS) provides name to address mapping within a

routing class (ex: IP). Network Address Translators (NATs) attempt to

provide transparent routing between hosts in disparate address realms

of the same routing class. Typically, NATs exist at the border of a

stub domain, hiding private addresses from external addresses. This

document identifies the need for DNS extensions to NATs and outlines

how a DNS Application Level Gateway (DNS_ALG) can meet the need.

DNS_ALG modifies payload transparently to alter address mapping of

hosts as DNS packets cross one address realm into another. The

document also illustrates the operation of DNS_ALG with specific

examples.

1. Introduction

Network Address Translators (NATs) are often used when 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.

Ideally speaking, a host name uniquely identifies a host and its

address is used to locate routes to the host. However, host name and

address are often not distinguished and used interchangeably by

applications. Applications embed IP address instead of host name in

payload. Examples would be e-mails that specify their MX server

address (ex: user@666.42.7.11) instead of server name (ex:

user@private.com) as sender ID; HTML files that include IP address

instead of names in URLs, etc. Use of IP address in place of host

name in payload represents a problem as the packet traverses a NAT

device because NATs alter network and transport headers to suit an

address realm, but not payload.

DNS provides Name to ad...