LOCAL-AREA NETWORK HARDWARE
The basic hardware components of a LAN are
cables, network interface cards, network servers,
peripherals, and workstations. These components are
covered in the material that follows.
CABLES
Several types of cables can be used in LAN
applications.
The selection of the type of cable
depends on several factors, such as maximum length
of a single cable run, security requirements, and the
capacity and speed of the system.
Twisted-Pair Cable
The twisted-pair cable is easy to install and costs
little on a per-foot basis. In some cases, existing
telephone cable may be used. Its disadvantages
include limitations in capacity and speed. It is also
susceptible to electrical interference unless it is
shielded.
Shielded Twisted-Pair Cable
The shielded twisted-pair cable is encased in an
RFI shield. The stranded wire used as a conductor is
manufactured with greater precision and is capable of
greater data transmission rates and longer cable runs.
Coaxial Cable
Coaxial cable networks have gained in popularity
because of their use in cable television. The
quantities of cable and connectors produced for cable
television have greatly reduced the prices of these
components for network users. Coaxial cable comes
in various thicknesses and is designated by a number:
RG-11, RG-58, RG-59, RG-62, and so forth. You can
use either baseband or broadband transmission
methods with coaxial cable.
Baseband coaxial systems transmit digital signals
unchanged over a single channel and have several
advantages. They are inexpensive, easy to install, and
have low maintenance. They also allow very high
data transmission rates. One disadvantage is that they
are limited to transmitting digital signals only.
In contrast, broadband coaxial systems require
the digital signal to be converted to an analog signal
before transmission and then back to digital by
modem at the receiving device. Broadband systems
support data, voice, and video signals that may be
transmitted simultaneously.
Disadvantages of
broadband systems are their higher installation costs
and complex maintenance.
Fiber-Optic Cable
Fiber-optic cable is the best choice if a secure
network is needed. Because the cable transmits light,
the transmissions are immune to interference caused
by electrical or electronic devices. Also, if your
network will run through an area of heavy industrial
activity or a work place with strong radio frequency
interference, fiber-optic cable is the most appropriate
choice. Other advantages of the fiber-optic cable are
that it lasts longer than other types of cable and can
carry many more channels. Its disadvantages include
its high price, poor connectivity, and low flexibility.
NETWORK INTERFACE CARD
To attach personal computers to the LAN, you
must connect a network interface card (NIC) to each
PC and attach the network cable to the NIC. The NIC
is nothing more than a circuit board that normally
plugs directly into one of the expansion slots inside a
PC. Sometimes, the NIC comes as a separate unit. In
this case, you plug it into the back of the PC. Most
NICs have their own built-in microprocessor(s)
designed to take care of network communications.
This relieves the PC’s main processor of this
responsibility. The type of cable used on the network
is determined by the type of LAN to be installed.
NETWORK SERVERS
Your understanding the concept of a server is
important to understanding how LANs work. A
server is a combination of hardware and software that
is used to manage the shared resources of the network.
The hardware may be a PC or a computer designed
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