Network Working Group A. Oppenheimer
Request for Comments: 1504 Apple Computer
August 1993
Appletalk Update-Based Routing Protocol:
Enhanced Appletalk Routing
Status of This Memo
This memo provides information for the Internet community. It does
not specify an Internet standard. Distribution of this memo is
unlimited.
Introduction
This memo is being distributed to members of the Internet community
to fully document an Apple protocol that may be running over the
Internet. While the issues discussed may not be directly relevant to
the research problems of the Internet, they may be interesting to a
number of researchers and implementers.
About This Document
This document provides detailed information about the AppleTalk
Update-based Routing Protocol (AURP) and wide area routing. AURP
provides wide area routing enhancements to the AppleTalk routing
protocols and is fully compatible with AppleTalk Phase 2. The
organization of this document has as its basis the three major
components of AURP:
AppleTalk tunneling, which allows AppleTalk data to pass through
foreign networks and over point-to-point links
the propagation of AppleTalk routing information between internet
routers connected through foreign networks or over point-to-point
links
the presentation of AppleTalk network information by an internet
router to nodes and other Phase 2-compatible routers on its local
internet
What This Document Contains
The chapters of this document contain the following information:
Chapter 1, "Introduction to the AppleTalk Update-Based Routing
Protocol," introduces the three major components of AURP and the
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RFC 1504 Appletalk Update-Based Routing Protocol August 1993
key wide area routing enhancements that AURP provides to the
AppleTalk routing protocols.
Chapter 2, "Wide Area AppleTalk Connectivity," provides
information about AppleTalk tunneling through IP internets and over
point-to-point links.
Chapter 3, "Propagating Routing Information With the AppleTalk
Update-Based Routing Protocol," describes the essential elements of
AURP, including the architectural model for update-based routing.
This chapter provides detailed information about the methods that
AURP uses to propagate routing information between internet routers
connected through tunnels.
Chapter 4, "Representing Wide Area Network Information," describes
optional features of AURP-some of which can also be implemented on
routers that use RTMP rather than AURP for routing-information
propagation. It gives detailed information about how an exterior
router represents imported network information to its local
internet and to other exterior routers. It describes network
hiding, device hiding, network-number remapping, clustering, loop
detection, hop-count reduction, hop-count weighting, and backup
paths.
The Appendix, "Implementation Details," provides information about
implementing AURP.
What You Need to Know
This document is intended for developers of AppleTalk wide area
routing products. It assumes familiarity with the AppleTalk network
system, internet routing, and wide area networking terms and
concepts.
Format of This RFC Document
The text of this document has been quickly prepared for RFC format.
However, the art is more complex and is not yet ready in this format.
We plan to incorporate the art in the future. Consult the official
APDA document, as indicated below, for the actual art.
For More Information
The following manuals and books from Apple Computer provide
additional information about AppleTalk networks. You can obtain books
published by Addison-Wesley at your local bookstore. Contact APDA,
Apple's source for developer tools, to obtain technical reference
materials for developers:
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RFC 1504 Appletalk Update-Based Routing Protocol August 1993
APDA
Apple Computer, Inc.
20525 Mariani Avenue, M/S 33-G
Cupertino, CA 95014-6299
These manuals provide information about some AppleTalk network
products:
The Apple Ethernet NB User's Guide explains how to install and use
an Apple Ethernet NB Card and EtherTalk software on an AppleTalk
network.
The Apple InteroPoll Network Administrator's Guide describes how
to perform maintenance and troubleshooting on an AppleTalk network
using InteroPoll, a network administrator's utility program.
The Apple Internet Router Administrator's Guide explains how to
install the Apple Internet Router Basic Connectivity Package and
how to use the Router Manager application program. It provides
information about setting up the router, configuring ports to
create local area and wide area internets, monitoring and
troubleshooting router operation, and planning your internet.
Using the AppleTalk/IP Wide Area Extension explains how to install
and use the AppleTalk/IP Wide Area Extension for the Apple Internet
Router. It provides information about tunneling through TCP/IP
networks, configuring an IP Tunnel access method for an Ethernet or
Token Ring port on the Apple Internet Router, troubleshooting IP
tunneling problems, and configuring MacTCP.
The AppleTalk Remote Access User's Guide explains how to use a
Macintosh computer to communicate with another Macintosh computer
over standard telephone lines to access information and resources
at a remote location.
The Apple Token Ring 4/16 NB Card User's Guide explains how to
install and operate the card and TokenTalk software on a Token Ring
network.
The MacTCP Administrator's Guide, version 1.1, explains how to
install and configure the MacTCP driver, which implements TCP/IP
(Transmission Control Protocol/Internet Protocol) on a Macintosh
computer.
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RFC 1504 Appletalk Update-Based Routing Protocol August 1993
The following books provide reference information about AppleTalk
networks:
The Advantages of AppleTalk Phase 2 provides a detailed
description of the enhanced internetworking capabilities of
AppleTalk Phase 2, and a brief guide to upgrading an AppleTalk
internet to AppleTalk Phase 2. Available from Apple Computer.
The AppleTalk Network System Overview provides a technical
introduction to the AppleTalk network system and its protocol
architecture. Published by Addison-Wesley Publishing Company.
The AppleTalk Phase 2 Introduction and Upgrade Guide is a detailed
guide to upgrading AppleTalk network hardware, drivers, and
application programs to AppleTalk Phase 2, and briefly describes
extensions to the AppleTalk network system that enhance its
support for large networks. Available from Apple Computer.
The AppleTalk Phase 2 Protocol Specification is an addendum to the
first edition of Inside AppleTalk that defines AppleTalk Phase 2
extensions to AppleTalk protocols that provide enhanced AppleTalk
addressing, routing, and naming services. Available from APDA.
Inside AppleTalk, second edition, is a technical reference that
describes the AppleTalk protocols in detail and includes
information about AppleTalk Phase 2. Published by Addison-Wesley
Publishing Company.
The Local Area Network Cabling Guide provides information about
network media, topologies, and network types. Available from Apple
Computer.
Planning and Managing AppleTalk Networks provides in-depth
information for network administrators about planning and managing
AppleTalk networks-including AppleTalk terms and concepts, and
information about network services, media, topologies, security,
monitoring and optimizing network performance, and
troubleshooting. Published by Addison-Wesley Publishing Company.
Understanding Computer Networks provides an overview of
networking-including basic information about protocol
architectures, network media, and topologies. Published by
Addison-Wesley Publishing Company.
The AppleTalk Update-Based Routing Protocol Specification is the
official Apple specification of AURP. It includes the artwork
currently missing from this document. Available from APDA.
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RFC 1504 Appletalk Update-Based Routing Protocol August 1993
Table of Contents
1. Introduction to the AppleTalk Update-Based Routing Protocol 6
Wide area routing enhancements provided by AURP 6
2. Wide Area AppleTalk Connectivity 7
AppleTalk tunneling 7
IP tunneling 14
Point-to-point tunneling 17
3. Propagating Routing Information With the AppleTalk Update-Based
Routing Protocol 18
AURP architectural model 18
Maintaining current routing information with AURP 20
AURP-Tr 21
One-way connections 22
Initial information exchange 22
Reobtaining routing information 28
Updating routing information 28
Processing update events 33
Router-down notification 38
Obtaining zone information 40
Hiding local networks from remote networks 44
AURP packet format 45
Error codes 55
4. Representing Wide Area Network Information 56
Network hiding 56
Device hiding 57
Resolving network-numbering conflicts 59
Zone-name management 65
Hop-count reduction 66
Routing loops 67
Using alternative paths 71
Network management 73
Appendix. Implementation Details 75
State diagrams 75
AURP table overflow 75
A scheme for updates following initial information exchange 75
Implementation effort for different components of AURP 76
Creating free-trade zones 77
Implementation details for clustering 78
Modified RTMP algorithms for a backup path 79
Security Considerations 82
Author's Address 82
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RFC 1504 Appletalk Update-Based Routing Protocol August 1993
1. INTRODUCTION TO THE APPLETALK UPDATE-BASED ROUTING PROTOCOL
The AppleTalk Update-based Routing Protocol (AURP) provides wide area
routing enhancements to the AppleTalk routing protocols and is fully
compatible with AppleTalk Phase 2. AURP consists of three major
components:
AppleTalk tunneling through foreign network systems-for example,
TCP/IP (Transmission Control Protocol/Internet Protocol) and over
point-to-point links
the propagation of routing information between internet routers
connected through foreign network systems or over point-to-point
links
the presentation of AppleTalk network information by an internet
router to nodes or to other Phase 2-compatible routers on its local
internet-in other words, on the AppleTalk internet connected
directly to the router
Chapter 3, "Propagating Routing Information With the AppleTalk
Update-Based Routing Protocol," describes the elements of AURP that
are essential for a minimal implementation of AURP. AURP includes
many optional features for the presentation of network information.
You can implement many of these optional features on routers that use
either AURP or RTMP (Routing Table Maintenance Protocol) for
routing-information propagation.
Figure 1-1 shows how the three major components of AURP interact.
<<Figure 1-1 Major components of AURP>>
Wide Area Routing Enhancements Provided by AURP
AURP provides AppleTalk Phase 2-compatible routing for large wide
area networks (WANs). Key wide area routing enhancements provided by
AURP include:
tunneling through TCP/IP internets and other foreign network
systems
point-to-point tunneling
basic security-including device hiding and network hiding
remapping of remote network numbers to resolve numbering conflicts
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RFC 1504 Appletalk Update-Based Routing Protocol August 1993
internet clustering to minimize routing traffic and routing-
information storage requirements
hop-count reduction to allow the creation of larger internets
improved use of alternate paths through hop-count weighting and
the designation of backup paths
2. WIDE AREA APPLETALK CONNECTIVITY
This chapter describes the wide area connectivity capabilities
provided by the AppleTalk Update-based Routing Protocol (AURP),
including:
AppleTalk tunneling
tunneling through TCP/IP internets
tunneling over point-to-point links
AppleTalk Tunneling
Tunneling allows a network administrator to connect two or more
native internets through a foreign network system to form a large
wide area network (WAN). For example, an AppleTalk WAN might consist
of two or more native AppleTalk internets connected through a tunnel
built on a TCP/IP internet. In such an AppleTalk WAN, native
internets use AppleTalk protocols, while the foreign network system
uses a different protocol family.
A tunnel connecting AppleTalk internets functions as a single,
virtual data link between the internets. A tunnel can be either a
foreign network system or a point-to-point link. Figure 2-1 shows an
AppleTalk tunnel.
<<Figure 2-1 AppleTalk tunnel>>
There are two types of tunnels:
dual-endpoint tunnels, which have only two routers on a tunnel-for
example, point-to-point tunnels
multiple-endpoint tunnels-herein referred to as multipoint tunnels-
which have two or more routers on a tunnel
AURP implements multipoint tunneling by providing mechanisms for data
encapsulation and the propagation of routing information to specific
routers.
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RFC 1504 Appletalk Update-Based Routing Protocol August 1993
Exterior Routers
An AppleTalk router with a port that connects an AppleTalk internet
to a tunnel is an exterior router. An exterior router alway