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CHAPTER 17 Management Information Systems 599

Telecommunications software provides a variety of communications support telecommunications software The
services such as establishing transmission speed, detecting and correcting trans- software that provides a variety of
communications support services such
mission errors, and protecting the network from unauthorized users. Telecommu-
as establishing transmission speed and
nications software may reside in computers and in communication processors. protecting the network from
There are three basic types of network structures or topologies, which are illus- unauthorized users
trated in Exhibit 17.1. The star network consists of a host computer connected to star network A network topology where
several, typically smaller computers. This topology is used when some processing a host computer is connected to
several, typically smaller computers and
must be centralized and some can be performed locally. Because all communica- all communications among computers
tions among computers in the network must pass through the host computer, this in the network must pass through the
topology is vulnerable to problems in the host computer. In a bus network, there is host computer
no host computer and all computers in the network share the same communica- bus network A network topology where
all computers in the network share the
tions channel—twisted-pair wire, coaxial cable, or fiber-optic cable. One advantage same communications channel and
of the bus network is that if one of the computers in the network fails, the other there is no host computer
computers in the network are not affected. One disadvantage of the bus network is ring network A network topology similar
that the communications channel can only handle one message at a time; if two to a bus network but where the
computers attempt to send a message at the same time, a “collision” occurs and the communications channel forms a
closed loop and hence information is
messages need to be resent. Consequently, as traffic in the network increases, per-
passed from one computer to the next
formance will degrade. A ring network is similar to a bus network in that there is no one in the ring in only one direction

EXHIBIT 17.1
The Three Basic Types of Network Topologies

Ring Network Star Network

Bus Network

Host Personal
computer computer Printer Hard disk

Source: James O’Brien, Introduction to Information Systems: Essentials for the Internetworked Enterprise, 9th edition (New York: McGraw-Hill/Irwin) 2000,
p. 157.

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