NCJ Number
101747
Date Published
Unknown
Length
9 pages
Annotation
This buyers guide for law enforcement users describes microcomputer local area networks (LAN's), their advantages and capabilities, and major considerations in selecting LAN's.
Abstract
A LAN is designed to connect microcomputers into an integrated communication system. Most LAN's allow users to share data, programs, mass storage devices, and printers. Bridges are available to link two LAN's of the same type; gateways perform protocol conversions between a LAN and a network of a different type. LAN's are privately owned, structured, limited in geographical scope, supportive of full connectivity, high speed, and commercially available. In choosing a LAN, the user must consider options in four major areas related to transmission, topology, access, and higher level services. Three transmission media are available for local area networking. These include copper wire (telephone wire), coaxial cable (television or similar cable), and optical fiber. The three basic LAN topologies (physical and logical arrangements of stations in relation to each other) are the linear bus, ring, and star. The most common access method is the carrier sense multiple access/collision detection (CSMA/CD) system; although CSMA/CD and electronic token passing both are recognized as valid data-collection avoidance schemes. Seven levels of network services have been established, but only the first two pertain directly to LAN's. These relate to physical and electrical characteristics and access management. Knowledge in these areas will facilitate choice of the LAN.