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 Oppenheimer [Page 1] 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: Oppenheimer [Page 2] 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. Oppenheimer [Page 3] 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. Oppenheimer [Page 4] 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 Oppenheimer [Page 5] 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. <
> 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 Oppenheimer [Page 6] 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. <
> 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. Oppenheimer [Page 7] 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