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Troubleshooting DECnet

   

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Troubleshooting DECnet

  

 

Digital Network Architecture

  

 

The Network Layer

  

 

The Transport Layer

  

 

Upper-Layer Protocols

  

 

Troubleshooting DECnet

  

 

DECnet: Connections to DEC Hosts Fail over Router (Router Problem)

  

 

DECnet: End Nodes Cannot Find Designated Router

  

 

DECnet: Router or End Node Sees Incorrect Designated Router

  

 

DECnet: Routers Not Establishing Adjacencies

  

 

DECnet: Routing Node Adjacencies Toggle Up and Down

  

 

DECnet: No Phase IV Connectivity over PhaseV Backbone

  

 

DECnet: Poor Performance

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Internetworking Troubleshooting Handbook

From: Internetworking Troubleshooting Handbook
Author: Systems Cisco; Kevin Downs
Publisher: Cisco Press (53)
More Information

11. Troubleshooting DECnet

Digital Equipment Corporation (Digital) developed the DECnet protocol family to provide a well-thought-out way for its computers to communicate with one another. The first version of DECnet, released in 1975, allowed two directly attached PDP-11 minicomputers to communicate. In more recent years, Digital has included support for nonproprietary protocols, but DECnet remains the most important of Digital's network product offerings.

DECnet is currently in its fifth major product release (sometimes called Phase V and referred to as DECnet/OSI in Digital literature). DECnet Phase V is a superset of the OSI protocol suite and supports all OSI protocols as well as several other proprietary and standard protocols that were supported in previous versions of DECnet. As with past changes to the protocol, DECnet Phase V is compatible with the previous release (Phase IV, in this case).

Digital Network Architecture

Contrary to popular belief, DECnet is not a network architecture at all but is, rather, a series of products conforming to Digital's Digital Network Architecture (DNA). Like most comprehensive network architectures from large systems vendors, DNA supports a large set of both proprietary and standard protocols. The list of DNA-supported technologies grows constantly as Digital implements new protocols. Figure 11-1 illustrates an incomplete snapshot of DNA and the relationship of some of its components to the OSI reference model.

Figure 11-1. DNA and the OSI Reference Model

As Figure 11-1 shows, DNA supports a variety of media and link implementations. Among these are well-known standards such as Ethernet, Token Ring, Fiber Distributed Data Interface (FDDI), IEEE 802.2, and X.25. DNA also offers a traditional point-to-point link-layer protocol called Digital Data Communications Message Protocol (DDCMP) and a 70-Mbps bus used in the VAX cluster called the computer-room interconnect bus (CI bus).

   

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