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Host groups: A multicast extension to the Internet Protocol (RFC0966)

IP.com Disclosure Number: IPCOM000004962D
Original Publication Date: 1985-Dec-01
Included in the Prior Art Database: 2001-Jul-12
Document File: 28 page(s) / 60K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

S.E. Deering: AUTHOR [+2]

Abstract

In this paper, we describe a model of multicast service we call host groups and propose this model as a way to support multicast in the DARPA Internet environment [14]. We argue that it is feasible to implement this facility as an extension of the existing "unicast" IP datagram model and mechanism.

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Network Working Group S. E. Deering Request for Comments: 966 D. R. Cheriton Stanford University

December 1985

Host Groups: A Multicast Extension to the Internet Protocol

1. Status of this Memo

This RFC defines a model of service for Internet multicasting and proposes an extension to the Internet Protocol (IP) to support such a multicast service. Discussion and suggestions for improvements are requested. Distribution of this memo is unlimited.

2. Acknowledgements

This memo was adapted from a paper [7] presented at the Ninth Data Communications Symposium. This work was sponsored in part by the Defense Advanced Research Projects Agency under contract N00039-83- K-0431 and National Science Foundation Grant DCR-83-52048.

The Internet task force on end-to-end protocols, headed by Bob Braden, has provided valuable input in the development of the host group model.

3. Introduction

In this paper, we describe a model of multicast service we call host groups and propose this model as a way to support multicast in the DARPA Internet environment [14]. We argue that it is feasible to implement this facility as an extension of the existing "unicast" IP datagram model and mechanism.

Multicast is the transmission of a datagram packet to a set of zero or more destination hosts in a network or internetwork, with a single address specifying the set of destination hosts. For example, hosts A, B, C and D may be associated with multicast address X. On transmission, a packet with destination address X is delivered with datagram reliability to hosts A, B, C and D.

Multicast has two primary uses, namely distributed binding and multi-destination delivery. As a binding mechanism, multicast is a robust and often more efficient alternative to the use of name servers for finding a particular object or service when a particular host address is not known. For example, in a distributed file system, all the file servers may be associated with one well-known multicast address. To bind a file name to a particular server, a client sends a query packet containing the file name to the file server multicast address, for delivery to all the file servers. The

Deering Cheriton [Page 1]

RFC 966 December 1985 Host Groups: A Multicast Extension to the Internet Protocol

server that recognizes the file name then responds to the client, allowing subsequent interaction directly with that server host. Even when name servers are employed, multicast can be used as the first step in the binding process, that is, finding a name server.

Multi-destination delivery is useful to several applications, including:

distributed, replicated databases [6,9].

conferencing [11].

distributed parallel computation, including distributed

gaming [2].

Ideally, multicast transmission to a set of hosts is not more complicated or expensive for the sender than transm...