What is Network Cabling?
Cable is the medium through which information usually
moves from one network device to another. There are several types of
cable which are commonly used with LANs. In some cases, a network will
utilize only one type of cable, other networks will use a variety of
cable types. The type of cable chosen for a network is related to the
network's topology, protocol, and size. Understanding the
characteristics of different types of cable and how they relate to other
aspects of a network is necessary for the development of a successful
network.
Unshielded Twisted Pair (UTP) Cable
Twisted pair cabling comes in two varieties: shielded
and unshielded. Unshielded twisted pair (UTP) is the most popular and is
generally the best option for business networks (See fig. 1).
Fig.1. Unshielded twisted
pair
The quality of UTP may vary from telephone-grade wire
to extremely high-speed cable. The cable has four pairs of wires inside
the jacket. Each pair is twisted with a different number of twists per
inch to help eliminate interference from adjacent pairs and other
electrical devices. The tighter the twisting, the higher the supported
transmission rate and the greater the cost per foot.
Unshielded Twisted Pair Connector
The standard connector for unshielded twisted pair
cabling is an RJ-45 connector. This is a plastic connector that looks
like a large telephone-style connector (See fig. 2). A slot allows the
RJ-45 to be inserted only one way. RJ stands for Registered Jack,
implying that the connector follows a standard borrowed from the
telephone industry. This standard designates which wire goes with each
pin inside the connector.
Fig. 2. RJ-45 connector
Shielded Twisted Pair (STP) Cable
A disadvantage of UTP is that it may be susceptible to
radio and electrical frequency interference. Shielded twisted pair (STP)
is suitable for environments with electrical interference; however, the
extra shielding can make the cables quite bulky. Shielded twisted pair
is often used on networks using Token Ring topology.
Coaxial Cable
Coaxial cabling has a single copper conductor at its
center. A plastic layer provides insulation between the center conductor
and a braided metal shield (See fig. 3). The metal shield helps to block
any outside interference from fluorescent lights, motors, and other
computers.
Fig. 3. Coaxial cable
Although coaxial cabling is difficult to install, it
is highly resistant to signal interference. In addition, it can support
greater cable lengths between network devices than twisted pair cable.
The two types of coaxial cabling are thick coaxial and thin coaxial.
Thin coaxial cable is also referred to as thinnet.
10Base2 refers to the specifications for thin coaxial cable carrying
Ethernet signals. The 2 refers to the approximate maximum segment length
being 200 meters. In actual fact the maximum segment length is 185
meters. Thin coaxial cable is popular in business networks, especially
linear bus networks.
Thick coaxial cable is also referred to as thicknet.
10Base5 refers to the specifications for thick coaxial cable carrying
Ethernet signals. The 5 refers to the maximum segment length being 500
meters. Thick coaxial cable has an extra protective plastic cover that
helps keep moisture away from the center conductor. This makes thick
coaxial a great choice when running longer lengths in a linear bus
network. One disadvantage of thick coaxial is that it does not bend
easily and is difficult to install.
Coaxial Cable Connectors
The most common type of connector used with coaxial
cables is the Bayone-Neill-Concelman (BNC) connector (See fig. 4).
Different types of adapters are available for BNC connectors, including
a T-connector, barrel connector, and terminator. Connectors on the cable
are the weakest points in any network. To help avoid problems with your
network, always use the BNC connectors that crimp, rather than screw,
onto the cable.
Fig. 4. BNC connector
Fiber Optic Cable
Fiber optic cabling consists of a center glass core
surrounded by several layers of protective materials (See fig. 5). It
transmits light rather than electronic signals eliminating the problem
of electrical interference. This makes it ideal for certain environments
that contain a large amount of electrical interference. It has also made
it the standard for connecting networks between buildings, due to its
immunity to the effects of moisture and lighting.
Fiber optic cable has the ability to transmit signals
over much longer distances than coaxial and twisted pair. It also has
the capability to carry information at vastly greater speeds. This
capacity broadens communication possibilities to include services such
as video conferencing and interactive services. The cost of fiber optic
cabling is comparable to copper cabling; however, it is more difficult
to install and modify. 10BaseF refers to the specifications for fiber
optic cable carrying Ethernet signals.
Fig.5. Fiber optic cable
Facts about fiber optic cables:
-
Outer insulating jacket is made of Teflon or PVC.
-
Kevlar fiber helps to strengthen the cable and prevent
breakage.
-
A plastic coating is used to cushion the fiber center.
-
Center (core) is made of glass or plastic fibers.
Fiber Optic Connector
The most common connector used with fiber optic cable
is an ST connector. It is barrel shaped, similar to a BNC connector. A
newer connector, the SC, is becoming more popular. It has a squared face
and is easier to connect in a confined space.
Wireless LANs
Not all networks are connected with cabling; some
networks are wireless. Wireless LANs use high frequency radio signals,
infrared light beams, or lasers to communicate between the workstations
and the file server or hubs. Each workstation and file server on a
wireless network has some sort of transceiver/antenna to send and
receive the data. Information is relayed between transceivers as if they
were physically connected. For longer distance, wireless communications
can also take place through cellular telephone technology, microwave
transmission, or by satellite.
Wireless LANs have several
disadvantages. They are very
expensive, provide poor security,
and are susceptible to interference from lights and electronic devices.
They are also slower than LANs
using cabling.
Network Cable Diagrams
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