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Browse Prior Art Database

IP to X.121 address mapping for DDN (RFC1236)

IP.com Disclosure Number: IPCOM000002051D
Original Publication Date: 1991-Jun-01
Included in the Prior Art Database: 2000-Sep-12
Document File: 6 page(s) / 11K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

L. Morales: AUTHOR [+2]

Abstract

All Internet hosts are assigned a four octet (32 bit) address composed of a network field and a local address field also known as the REST field [2] (see Figure 1 thru 3). Two basic forms of addresses are provided: (1) Physical addresses, correspond to the node number and DCE port number of the node to which the DTE is connected. (2) Logical addresses, are mapped transparently by DCE software into a corresponding physical network address.

This text was extracted from a ASCII Text document.
This is the abbreviated version, containing approximately 26% of the total text.

Network Working Group L. Morales

Request for Comments: 1236 P. Hasse

USAISEC

June 1991

IP to X.121 Address Mapping for DDN

Status of this Memo

This memo defines a standard way of converting IP addresses to CCITT

X.121 addresses and is the recommended standard for use on the

Internet, specifically for the Defense Data Network (DDN). This memo

provides information for the Internet community. It does not specify

an Internet standard. Distribution of this memo is unlimited.

1. Overview

The Defense Communication Agency (DCA) has stated that "DDN specifies

a standard for mapping Class A addresses to X.121 addresses."

Additionally DCA has stated that Class B and C IP to X.121 address

mapping "standards are the responsibility of the administration of

the Class B or C network in question". Therefore, there is NO

defined single standard way of converting Class B and Class C IP

addresses to X.121 addresses.

This is an important issue because currently there is no way for

administrators to define IP to X.121 address mapping. Without a

single standard, in a multi-vendor network environment, there is no

assurance that devices using IP and DDN X.25 will communicate with

each other.

The IP to X.121 address mapping of Class B and Class C IP addresses

shall be implemented as described below. This translation method is

a direct expansion of the algorithm described in the "MIL-STD: X.25,

DDN X.25 Host Interface Specification" [1]. The translation method

described below is TOTALLY independent of IP subnetting and of any

masking that may be used in support of IP subnetting.

2. Background

All Internet hosts are assigned a four octet (32 bit) address

composed of a network field and a local address field also known as

the REST field [2] (see Figure 1 thru 3). Two basic forms of

addresses are provided: (1) Physical addresses, correspond to the

node number and DCE port number of the node to which the DTE is

connected. (2) Logical addresses, are mapped transparently by DCE

software into a corresponding physical network address.

To provide flexibility, Internet addresses are divided into 3 primary

classes: Class A, Class B, and Class C. These classes allow for a

large number of small and medium sized networks. The network

addresses used within the Internet in Class A, B, and C networks are

divided between Research, Defense, Government, (Non-Defense) and

Commercial uses.

As described in the MIL-STD: X25, an IP address consists of the

ASCII text string representation of four decimal numbers separated by

periods, corresponding to the four octets of a thirty-two bit

Internet address. The four decimal numbers are referred to in this

memo as network (n), host (h), logica...