FREE online courses on Information Technology - Chapter 8 NETWORK &
COMMUNICATIONS IN I T - NETWORK
A networks connects a variety of
computers and other devices. Table below describes the networks discussed in
this chapter.
The largest computer network is the Internet. The largest
general-purpose network in the world is the public switched network used to carry more voice traffic around the world.
Here, one simply dials a number and establishes a point to point connection only
when it is needed. You probably use this network if you connect to a university
computer using personal computer with a modem. In addition to telephone, there
are special private network services also providing switched connections. Such a
network covers a huge distance. It would be considered a wide area network (WAN). Some
organizations want a network that is local to given area, and they might
configure it using private lines. This kind of network is known as a metropolitan area network (MAN).
Moving from the switched network, one might take a simple
connection between the two devices. One can generally wire directly for a mile
or two before the loss of signal
(attenuation)
becomes too great and modems are needed.
One way to reduce line costs is to have several terminals
connected to a device called a
multiplexer.
The multiplexer combines the signals from various low-speed terminals and
sends them over a higher-speed line. In time division multiplexing, the device
samples separate incoming signals and combines them on the output line. At the
receiving end, the signals must be demultiplexed. With a multiplexer, the speed
of the output line must equal the sum of the speeds of the input lines.
A concentrator is
a hardware device that collects messages from terminals and stores them if
necessary. The concentrator sends the message over a higher-speed line to
computer. Unlike the multiplexer, however, it can temporarily store the data, so
the capacity of the high-speed line does not have to equal the sum of the
capacities of the low-speed lines it serves.
Table: Types of
Networks and Examples
|
Type of network
|
Example
|
|
Network of networks
Public switched network
Wide area network (WAN)
Metropolitan area network (MAN)
Local area network (LAN)
|
The Internet
Voice telephony
The phone system
A campus network
PC network within a building
|
