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Issues affecting MARS Cluster Size (RFC2121)

IP.com Disclosure Number: IPCOM000002675D
Original Publication Date: 1997-Mar-01
Included in the Prior Art Database: 2000-Sep-13
Document File: 10 page(s) / 25K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

G. Armitage: AUTHOR

Abstract

IP multicast over ATM currently uses the MARS model [1] to manage the use of ATM pt-mpt SVCs for IP multicast packet forwarding. The scope of any given MARS services is the MARS Cluster - typically the same as an IPv4 Logical IP Subnet (LIS). Current IP/ATM networks are usually architected with unicast routing and forwarding issues dictating the sizes of individual LISes. However, as IP multicast is deployed as a service, the size of a LIS will only be as big as a MARS Cluster can be. This document provides a qualitative look at the issues constraining a MARS Cluster's size, including the impact of VC limits in switches and NICs, geographical distribution of cluster members, and the use of VC Mesh or MCS modes to support multicast groups.

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Network Working Group G. Armitage

Request for Comments: 2121 Bellcore

Category: Informational March 1997

Issues affecting MARS Cluster Size

Status of this Memo

This memo provides information for the Internet community. This memo

does not specify an Internet standard of any kind. Distribution of

this memo is unlimited.

Abstract

IP multicast over ATM currently uses the MARS model [1] to manage the

use of ATM pt-mpt SVCs for IP multicast packet forwarding. The scope

of any given MARS services is the MARS Cluster - typically the same

as an IPv4 Logical IP Subnet (LIS). Current IP/ATM networks are

usually architected with unicast routing and forwarding issues

dictating the sizes of individual LISes. However, as IP multicast is

deployed as a service, the size of a LIS will only be as big as a

MARS Cluster can be. This document provides a qualitative look at the

issues constraining a MARS Cluster's size, including the impact of VC

limits in switches and NICs, geographical distribution of cluster

members, and the use of VC Mesh or MCS modes to support multicast

groups.

1. Introduction

A MARS Cluster is the set of IP/ATM interfaces that are willing to

engage in direct, ATM level pt-mpt SVCs to perform IP multicast

packet forwarding [1]. Each IP/ATM interface (a MARS Client) must

keep state information regarding the ATM addresses of each leaf node

(recipient) of each pt-mpt SVC it has open. In addition, each MARS

Client receives MARS_JOIN and MARS_LEAVE messages from the MARS

whenever there is a requirement that Clients around the Cluster need

to update their pt-mpt SVCs for a given IP multicast group.

The definition of Cluster 'size' can mean two things - the number of

MARS Clients using a given MARS, and the geographic distribution of

MARS Clients. The number of MARS Clients in a Cluster impacts on the

amount of state information any given client may need to store while

managing outgoing pt- mpt SVCs. It also impacts on the average rate

of JOIN/LEAVE traffic that is propagated by the MARS on

ClusterControlVC, and the number of pt-mpt VCs that may need

modification each time a MARS_JOIN or MARS_LEAVE appears on

ClusterControlVC.

The geographic distribution of clients affects the latency between a

client issuing a MARS_JOIN, and it finally being added onto the pt-

mpt VCs of the other MARS Clients transmitting to the specified

multicast group. (This latency is made up of both the time to

propagate the MARS_JOIN, and the dela...