LANs: Basics

Gives basic information about Local Area Networks and how to distinguish different types

In todays usage of computer networks Local Area Networks (LANs) are most important. More than 50% of all installed computer systems in organizations are connected to a LAN.

This means, on the other hand, that only the organization itself is responsible for the selection and operation of their LAN. Other than with WANs or MANs there are no legal or political restrictions.

LANs can be characterized with the following points:

the network spreads over a small area, e. g. a single building or a cluster of buildings
the network consists of one transmission medium used for all operations within the network
the network runs at a high speed (from 1 Million bits per second to 100 Mbps)
it is a peer-to-peer network, that is, any device within the network can exchange data with any other device
it is owned by a single organization, which is responsible for its operation

LANs can be distinguished in four major points:

the topology of the network: bus or ring
the wiring layout: linear or star
the used transmission medium: twisted pair, coaxial cable (baseband, broadband), optical fibre
the used medium access control technique: CSMA/CD or token-passing

Together these points determine cost, capacity, effectiveness and performance of a LAN. What is more, they determine whether two LANs can be easily connected, a necessity that has become obvious during the last few years. The single points are not independent and cannot be decided in isolation.

Andreas Groessler, 11/08/1995