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Broadcasting Internet datagrams in the presence of subnets (RFC0922)

IP.com Disclosure Number: IPCOM000004333D
Original Publication Date: 1984-Oct-01
Included in the Prior Art Database: 2000-Oct-06
Document File: 10 page(s) / 23K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

J.C. Mogul: AUTHOR

Abstract

The use of broadcasts, especially on high-speed local area networks, is a good base for many applications. Since broadcasting is not covered in the basic IP specification [12], there is no agreed-upon way to do it, and so protocol designers have not made use of it. (The issue has been touched upon before, e.g. [6], but has not been the subject of a standard.)

This text was extracted from a ASCII Text document.
This is the abbreviated version, containing approximately 13% of the total text.

Network Working Group Jeffrey Mogul

Request for Comments: 922 Computer Science Department

Stanford University

October 1984

BROADCASTING INTERNET DATAGRAMS IN THE PRESENCE OF SUBNETS

Status of this Memo

We propose simple rules for broadcasting Internet datagrams on local

networks that support broadcast, for addressing broadcasts, and for

how gateways should handle them.

This RFC suggests a proposed protocol for the ARPA-Internet

community, and requests discussion and suggestions for improvements.

Distribution of this memo is unlimited.

Acknowledgement

This proposal here is the result of discussion with several other

people, especially J. Noel Chiappa and Christopher A. Kent, both of

whom both pointed me at important references.

1. Introduction

The use of broadcasts, especially on high-speed local area networks,

is a good base for many applications. Since broadcasting is not

covered in the basic IP specification [12], there is no agreed-upon

way to do it, and so protocol designers have not made use of it. (The

issue has been touched upon before, e.g. [6], but has not been the

subject of a standard.)

We consider here only the case of unreliable, unsequenced, possibly

duplicated datagram broadcasts (for a discussion of TCP broadcasting,

see [10].) Even though unreliable and limited in length, datagram

broadcasts are quite useful [1].

We assume that the data link layer of the local network supports

efficient broadcasting. Most common local area networks do support

broadcast; for example, Ethernet [7, 5], ChaosNet [9], token ring

networks [2], etc.

We do not assume, however, that broadcasts are reliably delivered.

(One might consider providing a reliable datagram broadcast protocol

as a layer above IP.) It is quite expensive to guarantee delivery of

broadcasts; instead, what we assume is that a host will receive most

of the broadcasts that are sent. This is important to avoid

excessive use of broadcasts; since every host on the network devotes

at least some effort to every broadcast, they are costly.

RFC 922 October 1984

Broadcasting Internet Datagrams in the Presence of Subnets

When a datagram is broadcast, it imposes a cost on every host that

hears it. Therefore, broadcasting should not be used

indiscriminately, but rather only when it is the best solution to a

problem.

2. Terminology

Because broadcasting depends on the specific data link layer in use

on a local network, we must discuss it with reference to both

physical networks and logical networks.

The terms we will use in referring to physical networks are, from the

point of view of the host sending or forwarding a broadcast:

Local Hardware Network

The physical link to which the host is attached...