IP over ATM: A Framework Document
RFC 1932
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RFC - Informational
(April 1996; No errata)
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2013-03-02
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RFC 1932 (Informational)
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Network Working Group R. Cole
Request for Comments: 1932 D. Shur
Category: Informational AT&T Bell Laboratories
C. Villamizar
ANS
April 1996
IP over ATM: A Framework Document
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 discussions of the IP over ATM working group over the last
several years have produced a diverse set of proposals, some of which
are no longer under active consideration. A categorization is
provided for the purpose of focusing discussion on the various
proposals for IP over ATM deemed of primary interest by the IP over
ATM working group. The intent of this framework is to help clarify
the differences between proposals and identify common features in
order to promote convergence to a smaller and more mutually
compatible set of standards. In summary, it is hoped that this
document, in classifying ATM approaches and issues will help to focus
the IP over ATM working group's direction.
1. Introduction
The IP over ATM Working Group of the Internet Engineering Task Force
(IETF) is chartered to develop standards for routing and forwarding
IP packets over ATM sub-networks. This document provides a
classification/taxonomy of IP over ATM options and issues and then
describes various proposals in these terms.
The remainder of this memorandum is organized as follows:
o Section 2 defines several terms relating to networking and
internetworking.
o Section 3 discusses the parameters for a taxonomy of the
different ATM models under discussion.
o Section 4 discusses the options for low level encapsulation.
Cole, Shur & Villamizar Informational [Page 1]
RFC 1932 IP over ATM: A Framework Document April 1996
o Section 5 discusses tradeoffs between connection oriented and
connectionless approaches.
o Section 6 discusses the various means of providing direct
connections across IP subnet boundaries.
o Section 7 discusses the proposal to extend IP routing to better
accommodate direct connections across IP subnet boundaries.
o Section 8 identifies several prominent IP over ATM proposals that
have been discussed within the IP over ATM Working Group and
their relationship to the framework described in this document.
o Section 9 addresses the relationship between the documents
developed in the IP over ATM and related working groups and the
various models discussed.
2. Definitions and Terminology
We define several terms:
A Host or End System: A host delivers/receives IP packets to/from
other systems, but does not relay IP packets.
A Router or Intermediate System: A router delivers/receives IP
packets to/from other systems, and relays IP packets among
systems.
IP Subnet: In an IP subnet, all members of the subnet are able to
transmit packets to all other members of the subnet directly,
without forwarding by intermediate entities. No two subnet
members are considered closer in the IP topology than any other.
From an IP routing and IP forwarding standpoint a subnet is
atomic, though there may be repeaters, hubs, bridges, or switches
between the physical interfaces of subnet members.
Bridged IP Subnet: A bridged IP subnet is one in which two or
more physically disjoint media are made to appear as a single IP
subnet. There are two basic types of bridging, media access
control (MAC) level, and proxy ARP (see section 6).
A Broadcast Subnet: A broadcast network supports an arbitrary
number of hosts and routers and additionally is capable of
transmitting a single IP packet to all of these systems.
A Multicast Capable Subnet: A multicast capable subnet supports
a facility to send a packet which reaches a subset of the
destinations on the subnet. Multicast setup may be sender
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RFC 1932 IP over ATM: A Framework Document April 1996
initiated, or leaf initiated. ATM UNI 3.0 [4] and UNI 3.1
support only sender initiated while IP supports leaf initiated
join. UNI 4.0 will support leaf initiated join.
A Non-Broadcast Multiple Access (NBMA) Subnet: An NBMA supports
an arbitrary number of hosts and routers but does not
natively support a convenient multi-destination connectionless
transmission facility, as does a broadcast or multicast capable
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