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IP Multicast over Token-Ring Local Area Networks (RFC1469)

IP.com Disclosure Number: IPCOM000002298D
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2000-Sep-12
Document File: 4 page(s) / 8K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

T. Pusateri: AUTHOR

Abstract

This document specifies a method for the transmission of IP multicast datagrams over Token-Ring Local Area Networks. Although an interim solution has emerged and is currently being used, it is the intention of this document to specify a more efficient means of transmission using an assigned Token-Ring functional address.

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This is the abbreviated version, containing approximately 39% of the total text.

Network Working Group T. Pusateri

Request for Comments: 1469 Consultant

June 1993

IP Multicast over Token-Ring Local Area Networks

Status of this Memo

This RFC specifies an IAB standards track protocol for the Internet

community, and requests discussion and suggestions for improvements.

Please refer to the current edition of the "IAB Official Protocol

Standards" for the standardization state and status of this protocol.

Distribution of this memo is unlimited.

Abstract

This document specifies a method for the transmission of IP multicast

datagrams over Token-Ring Local Area Networks. Although an interim

solution has emerged and is currently being used, it is the intention

of this document to specify a more efficient means of transmission

using an assigned Token-Ring functional address.

Introduction

IP multicasting provides a means of transmitting IP datagrams to a

group of hosts. A group IP address is used as the destination

address in the IP datagram as documented in STD 5, RFC 1112 [1].

These group addresses, also referred to as Class D addresses, fall in

the range from 224.0.0.0 to 239.255.255.255. A standard method of

mapping IP multicast addresses to media types such as ethernet and

fddi exist in [1] and RFC 1188 [2]. This document attempts to define

the mapping for an IP multicast address to the corresponding Token-

Ring MAC address.

Background

The Token-Ring Network Architecture Reference [3] provides several

types of addressing mechanisms. These include both individual

(unicast) and group addresses (multicast). A special subtype of

group addresses are called functional addresses and are indicated by

a bit in the destination MAC address. They were designed for widely

used functions such as ring monitoring, NETBIOS, Bridge, and Lan

Manager frames. There are a limited number of functional addresses,

31 in all, and therefore several unrelated functions must share the

same functional address.

It would be most desirable if Token-Ring could use the same mapping

as ethernet and fddi for IP multicast to hardware multicast

addressing. However, current implementations of Token-Ring

controller chips cannot support this. To see why, we must first

examine the Destination MAC address format.

Destination Address Format

The destination MAC address consists of six octets. In the following

diagram of a MAC address, the order of transmission of the octets is

from top to bottom (octet 0 to octet 5), and the order of

transmission of the bits within each octet is from right to left (bit

0 to bit 7). This is the so-called "canonical" bit order for IEEE

802.2 addresses. Addresses supplied to or received from token ring

interfaces are usually laid out in memory with the bits of each octet

in the opposite order from that illustrated, i...