|AURP, AppleTalk Update-based Routing Protocol|
|Protocol suites:||Appletalk, TCP/IP.|
|Protocol type:||Application layer routing protocol.|
RFC 1504, pages 1, 6 and 7:
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 through foreign network systems-for example, TCP/IP (Transmission Control Protocol/Internet Protocol) and over point-to-point links.
- The propagation of AppleTalk 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.
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.
Wide Area Routing Enhancements. 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.
- 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.
The wide area connectivity capabilities provided by the AppleTalk Update-based Routing Protocol (AURP) includes:
- AppleTalk tunneling.
- Tunneling through TCP/IP internets.
- Tunneling over point-to-point links AppleTalk.
RFC 1504, page 7:
AppleTalk 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.
There are two types of tunnels, dual endpoint tunnels and multiple endpoint tunnels.
AURP implements multipoint tunneling by providing mechanisms for data encapsulation and the propagation of routing information to specific routers.
RFC 1504, pages 16 and 17:
The AppleTalk Data Packet Format for IP Tunneling consists of: Protocol headers which precede an AppleTalk data packet that is forwarded across an IP tunnel by an exterior router:
- A data-link header.
- An IP header.
- An User Datagram Protocol (UDP) header.
- A domain header.
An exterior router encapsulates AppleTalk data packets in UDP packets when forwarding them through its UDP port 387, across an IP tunnel, to UDP port 387 on another exterior router. When encapsulating data packets, an exterior router should always use UDP checksums. When a destination exterior router receives the UDP packets at UDP port 387, it decapsulates the packets.
RFC 1504, pages 17 and 18:
Point-to-Point Tunneling. In point-to-point tunneling, two remote AppleTalk local area networks (LANs) connected to half-routers communicate with one another over a point-to-point link. A point-to-point link may consist of modems communicating over a standard telephone line or a leased line, such as a T1 line.
Generally, exterior routers use null domain identifiers on point-to- point links, because there is no IP address to be administrated and the opposite end of the tunnel is already uniquely identified. However, an exterior router may use other domain-identifier formats.
The Point-to-Point Protocol (PPP) is a data-link-layer protocol that provides a standard method of encapsulating and decapsulating network-layer protocol information, and transmitting that information over point-to-point links. PPP includes an extensible Link Control Protocol (LCP) and a suite of Network Control Protocols (NCPs) that configure, enable, and disable various network-layer protocols.
When using AURP for routing-information propagation, a half-router uses a specific PPP protocol type to identify AURP routing-information packets-that is, packets preceded by a domain header. PPP provides separate channels for AppleTalk data packets and AppleTalk routing-information packets. Thus, a half-router can use DDP encapsulation to send AppleTalk data packets without including their domain headers. When using AURP, a half-router should accept both AppleTalk data packets that are preceded by domain headers and DDP-encapsulated packets.
|MAC header||IP header||UDP header||AURP packet|
[RFC 1378] The PPP AppleTalk Control Protocol (ATCP).
[RFC 1504] Appletalk Update-Based Routing Protocol: Enhanced Appletalk Routing.