Chapter 22: DECnet Details

This section presents some background information on DECnet that is not necessary to use DECnet effectively, but provides a better understanding of the underlying technology.

DECnet Routing

Some DECnet nodes are routers, while others are end nodes. Routers maintain a database of the network layout and can forward network traffic to and from end nodes. Routers may have physical connections to two or more separate local area networks (LANs) and have the responsibility to forward information between nodes on separate LANs. Routers can also perform any function that an end node can.

DECnet routers maintain tables allowing them to forward traffic between any two nodes properly, even if there are several routers between the nodes or there are several possible paths.

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LANs

A networking scheme like DECnet or TCP/IP is a conceptual abstraction used on collections of concrete networks—for example, LANs. A LAN consists of one or more nodes connected by a physical network medium, such as an Ethernet cable (including any hubs). All nodes on a LAN may communicate directly with one another because they share the same physical medium. A DECnet or TCP/IP network may consist of many separate LANs, with DECnet or TCP/IP assuming responsibility for connecting them and directing traffic via routers. Different networking schemes including DECnet, TCP/IP, and many others may coexist on the same physical networks at the same time.

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DECnet end nodes can communicate directly with other DECnet nodes on the same LAN, but must rely on a router to communicate with machines on other LANs.

Routing is based on cost, an arbitrary value assigned by the network manager to each step in a possible path (hops). Between two nodes, the path with the least total cost is preferred. When network problems occur, or when certain routers are unavailable, a new path is chosen at the next lowest cost.



Getting Started with OpenVMS(c) A Guide for New Users
Getting Started with OpenVMS: A Guide for New Users (HP Technologies)
ISBN: 1555582796
EAN: 2147483647
Year: 2005
Pages: 215

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