Using the MARS Model in non-ATM NBMA Networks (RFC2269)
Original Publication Date: 1998-Jan-01
Included in the Prior Art Database: 2019-Feb-15
Internet Society Requests For Comment (RFCs)
This document is intended to state the obvious equivalences, and explain the less obvious implications. This memo provides information for the Internet community. It does not specify an Internet standard of any kind.
Network Working Group G. Armitage Request for Comments: 2269 Lucent Technologies Category: Informational January 1998
Using the MARS Model in non-ATM NBMA Networks
Status of this Memo
This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.
Copyright (C) The Internet Society (1998). All Rights Reserved.
Initially developed for IP over ATM, the RFC 2022 (MARS) model is also applicable to other NBMA networks that provide the equivalent of switched, point to multipoint connections. This short document is intended to state the obvious equivalences, and explain the less obvious implications. No changes to the MARS model per se are suggested or required. RFC 2022 is not required over NBMA networks that offer Ethernet-like group addressing functionality.
Most network layer models, like the one described in STD 5, RFC 1112  for IP multicasting, assume sources may send their packets to an abstract ’multicast group addresses’. Link layer support for such an abstraction is assumed to exist, and is provided by technologies such as Ethernet.
Some NBMA networks (e.g. ATM using UNI3.0 or UNI3.1 signaling [4,5]) do not support a multicast (or group) address abstraction. In these environments multicasting is typically supported through point to multipoint calls (or emulated with multiple point to point calls). The MARS model (RFC 2022)  was originally developed by the IP over ATM working group, and so uses ATM-centric descriptive language. For completeness this memo explains how RFC 2022 can be applied to other NBMA technologies.
Armitage Informational [Page 1]
RFC 2269 MARS Model in non-ATM NBMA Networks January 1998
2. RFC 2022’s basic assumptions.
Section 3 of  describes the basic assumptions that the MARS model makes about the services available from the link layer network (using ATM as the specific case). In summary these are:
The ATM model broadly describes an ’AAL User’ as any entity that establishes and manages VCs and underlying AAL services to exchange data. An IP over ATM interface is a form of ’AAL User’
The most fundamental limitations of UNI 3.0/3.1’s multicast support are:
Only point to multipoint, unidirectional VCs may be established.
Only the root (source) node of a given VC may add or remove leaf nodes.
Leaf nodes are identified by their unicast ATM addresses.
Given this point to multipoint call service, the MARS document goes on to describe two architectures for emulating multipoint to multipoint IP multicasting - the VC Mesh, and the Multicast Server. In either case it was assumed that IP/ATM interfaces (whether in routers or hosts) are allowed to originate and manage outgoing point to multipoint calls without network operator intervention or manual provisioning.
The MARS document also specifies that AAL5 be used for all SVCs, implying a requirement that the underlying link service supports the...