Information Technology Reference
In-Depth Information
top are personal area networks, networks that are meant for one person.
Beyond these come longer-range networks. These can be divided into local,
metropolitan, and wide area networks, each with increasing scale. Finally,
the connection of two or more networks is called an Internetwork. The
worldwide Internet is certainly the best-known (but not the only) example
of an Internetwork.
2.2.2.1 Personal Area Networks
PANs (Personal Area Networks) let devices communicate over the range of
a person. A common example is a wireless network that connects a com-
puter with its peripherals. Almost every computer has an attached monitor,
keyboard, mouse, and printer. Without using wireless, this connection must
be done with cables. So many new users have a hard time finding the right
cables and plugging them into the right little holes (even though they are
usually color coded) that most computer vendors offer the option of sending
a technician to the user's home to do it. To help these users, some companies
got together to design a short-range wireless network called Bluetooth to
connect these components without wires. The idea is that if your devices
have Bluetooth, then you need no cables. You just put them down, turn them
on, and they work together. For many people, this ease of operation is a big
plus. PANs can also be built with other technologies that communicate over
short ranges, such as RFID on smartcards and library topics.
2.2.2.2 Local Area Networks
Wireless LANs are very popular these days, especially in homes, older office
buildings, cafeterias, and other places where it is too much trouble to install
cables. A LAN is a privately owned network that operates within and nearby
a single building like a home, office, or factory. LANs are widely used to
connect personal computers and consumer electronics to let them share
resources (e.g., printers) and exchange information. When LANs are used by
companies, they are called enterprise networks.
In these systems, every computer has a radio modem and an antenna that
it uses to communicate with other computers. In most cases, each computer
talks to a device in the ceiling called AP (access point), wireless router, or
base station, relays packets between wireless computers and also between
them and the Internet. However, if other computers are close enough, they
can communicate directly with one another in a peer-to-peer configuration.
There is a standard for wireless LANs called IEEE 802.11, popularly known
as Wi-Fi, which has become very widespread. It runs at speeds anywhere
from eleven to hundreds of megabytes per second. Wired LANs use a range
of different transmission technologies. Most of them use copper wires, but
some use optical fiber. LANs are restricted in size, which means that the
worst-case transmission time is bounded and known in advance. Knowing
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