Information Technology Reference
In-Depth Information
broadcasting of all messages. This allows tokenring messages to be
somewhat longer than those in Ethernet, if additional length is
needed.
Historically, both Ethernet and tokenring networks have had
strong advocates, and both types of networks have been used exten
sively. When under development, both types of networks had strong
positive characteristics, and both could achieve good speeds for the
transmission of information. In recent years, however, advances in
technology have increased communication speeds for Ethernet net
works, so that they surpass the tokenring configuration, and
Ethernet networks have come to dominate other wirebased forms.
What type of network configuration does your school or business
use? If it is indeed an Ethernet connection, you can see first hand
how thousands of people can communicate via computer using one
Ethernet network.
arbitrarily large number of computers?
Star networks rely on a single, central machine for communica
tion, and Ethernet networks depend logically upon a single cable for
communication. Limitations arise whenever technology depends on
a single device or medium. Also, wires are subject to electrical noise
and power loss, and such matters become more significant as the
length of a wire increases. Expansion of networks must take these
factors into account. Here are some ways this is done.
We have already noted that each computer in a star network
places some demands on a central machine. Thus, as the number of
computers in a network increases, the demand placed on the central
machines increases. Eventually, the demands made on the central
machine will slow overall processing down. The central machine
can do only a certain amount of work, and performance suffers as
that level of activity is approached and exceeded.
Furthermore, demands from separate computers rarely are
evenly distributed. For example, in a business office, users likely
place relatively heavy demands on computers during the day, but re
quire little service from networks at night. Also, during the day,
computer activity would likely be low during breaks or meetings,
