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Multi-LAN address resolution (RFC0925)

IP.com Disclosure Number: IPCOM000004338D
Original Publication Date: 1984-Oct-01
Included in the Prior Art Database: 2000-Oct-09
Document File: 13 page(s) / 30K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

J. Postel: AUTHOR

Abstract

The problem of treating a set of local area networks (LANs) as one Internet network has generated some interest and concern. It is inappropriate to give each LAN within an site a distinct Internet network number. It is desirable to hide the details of the interconnections between the LANs within an site from people, gateways, and hosts outside the site. The question arises on how to best do this, and even how to do it at all. One proposal is to use "explicit subnets" [1]. The explicit subnet scheme is a call to recursively apply the mechanisms the Internet uses to manage networks to the problem of managing LANs within one network. In this note I urge another approach: the use of "transparent subnets" supported by a multi-LAN extension of the Address Resolution Protocol [2].

This text was extracted from a ASCII document.
This is the abbreviated version, containing approximately 9% of the total text.

Network Working Group J. Postel

Request for Comments: 925 ISI

October 1984

Multi-LAN Address Resolution

STATUS OF THIS MEMO

This memo is prompted by RFC-917 by Jeffery Mogul on "Internet

Subnets". In that memo, Mogul makes a case for the use of "explicit

subnets" in a multi-LAN environment. In this memo, I attempt to make

a case for "transparent subnets". This RFC suggests a proposed

protocol for the ARPA-Internet community, and requests discussion and

suggestions for improvements. Distribution of this memo is

unlimited.

INTRODUCTION

The problem of treating a set of local area networks (LANs) as one

Internet network has generated some interest and concern. It is

inappropriate to give each LAN within an site a distinct Internet

network number. It is desirable to hide the details of the

interconnections between the LANs within an site from people,

gateways, and hosts outside the site. The question arises on how to

best do this, and even how to do it at all. One proposal is to use

"explicit subnets" [1]. The explicit subnet scheme is a call to

recursively apply the mechanisms the Internet uses to manage networks

to the problem of managing LANs within one network. In this note I

urge another approach: the use of "transparent subnets" supported by

a multi-LAN extension of the Address Resolution Protocol [2].

OVERVIEW

To quickly review the Address Resolution Protocol (ARP). Each host

on a broadcast LAN knows both its own physical hardware address (HA)

on the LAN and its own Internet Address (IA). When Host-A is given

the IA of Host-B and told to send a datagram to it, Host-A must find

the HA that corresponds to Host-B's IA. To do this Host-A forms an

ARP packet that contains its own HA and IA and the IA of the

destination host (Host-B). Host-A broadcasts this ARP packet. The

hosts that receive this ARP packet check to see if they are

destination sought. If so, they (it should be only Host-B) send a

reply specifically addressed to the originator of the query (Host-A)

and supplying the HA that was needed. The Host-A now has both the HA

and the IA of the destination (Host-B). The Host-A adds this

information to a local cache for future use.

Note: The ARP is actually more general purpose than this brief

sketch indicates.

RFC 925 October 1984

Multi-LAN Address Resolution

The idea in this memo is to extend the ARP to work i...