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VENUS - Very Extensive Non-Unicast Service (RFC2191)

IP.com Disclosure Number: IPCOM000002749D
Original Publication Date: 1997-Sep-01
Included in the Prior Art Database: 2000-Sep-13
Document File: 10 page(s) / 29K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

G. Armitage: AUTHOR

Abstract

The MARS model (RFC2022) provides a solution to intra-LIS IP multicasting over ATM, establishing and managing the use of ATM pt- mpt SVCs for IP multicast packet forwarding. Inter-LIS multicast forwarding is achieved using Mrouters, in a similar manner to which the "Classical IP over ATM" model uses Routers to inter-connect LISes for unicast traffic. The development of unicast IP shortcut mechanisms (e.g. NHRP) has led some people to request the development of a Multicast equivalent. There are a number of different approaches. This document focuses exclusively on the problems associated with extending the MARS model to cover multiple clusters or clusters spanning more than one subnet. It describes a hypothetical solution, dubbed "Very Extensive NonUnicast Service" (VENUS), and shows how complex such a service would be. It is also noted that VENUS ultimately has the look and feel of a single, large cluster using a distributed MARS. This document is being issued to help focus ION efforts towards alternative solutions for establishing ATM level multicast connections between LISes.

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Network Working Group G. Armitage

Request for Comments: 2191 Lucent Technologies

Category: Informational September 1997

VENUS - Very Extensive Non-Unicast Service

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

The MARS model (RFC2022) provides a solution to intra-LIS IP

multicasting over ATM, establishing and managing the use of ATM pt-

mpt SVCs for IP multicast packet forwarding. Inter-LIS multicast

forwarding is achieved using Mrouters, in a similar manner to which

the "Classical IP over ATM" model uses Routers to inter-connect LISes

for unicast traffic. The development of unicast IP shortcut

mechanisms (e.g. NHRP) has led some people to request the

development of a Multicast equivalent. There are a number of

different approaches. This document focuses exclusively on the

problems associated with extending the MARS model to cover multiple

clusters or clusters spanning more than one subnet. It describes a

hypothetical solution, dubbed "Very Extensive NonUnicast Service"

(VENUS), and shows how complex such a service would be. It is also

noted that VENUS ultimately has the look and feel of a single, large

cluster using a distributed MARS. This document is being issued to

help focus ION efforts towards alternative solutions for establishing

ATM level multicast connections between LISes.

1. Introduction

The classical model of the Internet running over an ATM cloud

consists of multiple Logical IP Subnets (LISs) interconnected by IP

Routers [1]. The evolving IP Multicast over ATM solution (the "MARS

model" [2]) retains the classical model. The LIS becomes a "MARS

Cluster", and Clusters are interconnected by conventional IP

Multicast routers (Mrouters).

The development of NHRP [3], a protocol for discovering and managing

unicast forwarding paths that bypass IP routers, has led to some

calls for an IP multicast equivalent. Unfortunately, the IP

multicast service is a rather different beast to the IP unicast

service. This document aims to explain how much of what has been

learned during the development of NHRP must be carefully scrutinized

before being re-applied to the multicast scenario. Indeed, the

service provided by the MARS and MARS Clients in [2] are almost

orthogonal to the IP unicast service over ATM.

For the sake of discussion, let's call this hypothetical multicast

shortcut discovery protocol...