| Networks can be divided into two basic
categories: Local Area Networks (LANs) and Wide Area Networks (WANs).
LANs are made up of groups of computers (nodes) that have simultaneous
access to common high bandwidth media. Media can be copper wire, fiber
optic cable or even air as with wireless LANs. Bandwidth is the data
carrying capacity of the media and LAN technology being used. Each
node or computer (in most cases) gains access to the network media
through a Network Interface Card (NIC), which is installed in the
computer.
These nodes are connected in a
relatively confined geographical location where the distance between
nodes is normally less than 500 feet or approximately 150 meters. Most
LANs cover a small area, usually less than 10,000 square feet or
approximately 1000 square meters. Distances between nodes can be
greater than a mile and still be considered a LAN, but this is
uncommon. A node is an endpoint on the network and can be a
workstation, a server or a printer. LANs can have as few as two
computers or as many as thousands. They can occupy a single room or
span multiple buildings, as with a campus environment.
LANs provide high-speed communications
between all interconnected nodes or devices. This allows users to
share network resources such as documents, databases, applications,
printers, and Internet connections. High-speed communication is
defined here as 10 Mbps (10 million bits per second) or faster.
Current LAN technologies support speeds of over 1Gbps (Gigabits per
second or 1,000 million bits per second).
LANs are usually interconnected by
physical cabling such as copper or fiber optic, however in recent
years, wireless LANs have become more common. All cabling, conduit, and
interconnected
network equipment, such as hubs and switches are typically owned by the
organization that uses the LAN. Examples of LAN technologies or
architectures include Ethernet, Token Ring and FDDI (Fiber Distributed
Data Interface).
Figure
summarizes the characteristics of a LAN and Figure
shows a LAN with nodes interconnected by a multi-port switch in a star
topology, which is very common in today's LAN network designs.
Topologies will be covered later in this chapter. Multi-port switches
can be interconnected which allow a large number of workstations to be
on the same LAN. While routers can be used to divide the LAN into
multiple segments for improved performance and security.
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