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Chapter 7 Telecommunications, the Internet, and Wireless Technology 283

Client/server computing has largely replaced centralized mainframe
computing in which nearly all of the processing takes place on a central large
mainframe computer. Client/server computing has extended computing to
departments, workgroups, factory floors, and other parts of the business that
could not be served by a centralized architecture. The Internet is the largest
implementation of client/server computing.

Packet Switching
Packet switching is a method of slicing digital messages into parcels called
packets, sending the packets along different communication paths as they
become available, and then reassembling the packets once they arrive
at their destinations (see Figure 7.3). Prior to the development of packet
switching, computer networks used leased, dedicated telephone circuits to
communicate with other computers in remote locations. In circuit-switched
networks, such as the telephone system, a complete point-to-point circuit is
assembled, and then communication can proceed. These dedicated circuit-
switching techniques were expensive and wasted available communications
capacity—the circuit was maintained regardless of whether any data were
being sent.
Packet switching makes much more efficient use of the communica-
tions capacity of a network. In packet-switched networks, messages are first
broken down into small fixed bundles of data called packets. The packets
include information for directing the packet to the right address and for
checking transmission errors along with the data. The packets are transmit-
ted over various communications channels using routers, each packet traveling
independently. Packets of data originating at one source will be routed through
many different paths and networks before being reassembled into the original
message when they reach their destinations.

FIGURE 7.3 PACKED-SWITCHED NETWORKS AND PACKET
COMMUNICATIONS

Data are grouped into small packets, which are transmitted independently over various communica-
tions channels and reassembled at their final destination.

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