Computer Networks 3150710

Practical -2

AIM:- Study of different types of network cables and practically implement the
cross-wired cable and straight through cable using clamping tool.

To connect two or more computers or networking devices in a network, network cables are used. There
are three types of network cables; coaxial, twisted-pair, and fiber-optic.

1) Coaxial cable
This cable contains a conductor, insulator, braiding, and sheath. The sheath covers the braiding, the
braiding covers the insulation, and the insulation covers the conductor.

The following image shows these components.

Sheath
This is the outer layer of the coaxial cable. It protects the cable from physical damage.

Braided shield
This shield protects signals from external interference and noise. This shield is built from the same metal
that is used to build the core.

Insulation
Insulation protects the core. It also keeps the core separate from the braided shield. Since both the core
and the braided shield use the same metal, without this layer, they will touch each other and create a
short-circuit in the wire.

Conductor
The conductor carries electromagnetic signals. Based on conductor a coaxial cable can be categorized
into two types; single-core coaxial cable and multi-core coaxial cable.

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A single-core coaxial cable uses a single central metal (usually copper) conductor, while a multi-core
coaxial cable uses multiple thin strands of metal wires. The following image shows both types of cable.

The coaxial cables were not primarily developed for the computer network. These cables were developed
for general purposes. They were in use even before computer networks came into existence. They are
still used even their use in computer networks has been completely discontinued.

At the beginning of computer networking, when there were no dedicated media cables available for
computer networks, network administrators began using coaxial cables to build computer networks.

Because of its low cost and long durability, coaxial cables were used in computer networking for nearly
two decades (the 80s and 90s). Coaxial cables are no longer used to build any type of computer network.

Specifications of coaxial cables:

Coaxial cables have been in use for the last four decades. During these years, based on several factors
such as the thickness of the sheath, the metal of the conductor, and the material used in insulation,
hundreds of specifications have been created to specify the characteristics of coaxial cables.

• Coaxial cable uses RG rating to measure the materials used in shielding and conducting cores.
• RG stands for the Radio Guide. Coaxial cable mainly uses radio frequencies in transmission.
• Impedance is the resistance that controls the signals. It is expressed in the ohms.
• AWG stands for American Wire Gauge. It is used to measure the size of the core. The larger the
AWG size, the smaller the diameter of the core wire.

2) Twisted-pair cables
The twisted-pair cable was primarily developed for computer networks. This cable is also known
as Ethernet cable. Almost all modern LAN computer networks use this cable.

This cable consists of color-coded pairs of insulated copper wires. Every two wires are twisted around
each other to form pair. Usually, there are four pairs. Each pair has one solid color and one stripped color
wire. Solid colors are blue, brown, green, and orange. In stripped color, the solid color is mixed with the
white color.

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Based on how pairs are stripped in the plastic sheath, there are two types of twisted-pair cable; UTP and
STP.

In the UTP (Unshielded twisted-pair) cable, all pairs are wrapped in a single plastic sheath.

In the STP (Shielded twisted-pair) cable, each pair is wrapped with an additional metal shield, then all
pairs are wrapped in a single outer plastic sheath.

Similarities and differences between STP and UTP cables

• Both STP and UTP can transmit data at 10Mbps, 100Mbps, 1Gbps, and 10Gbps.
• Since the STP cable contains more materials, it is more expensive than the UTP cable.
• Both cables use the same RJ-45 (registered jack) modular connectors.
• Both cables can accommodate a maximum of 1024 nodes in each segment.
• The STP provides more noise and EMI resistance than the UTP cable.
• The maximum segment length for both cables is 100 meters or 328 feet.

The following image shows both types of twisted-pair cables.

To learn how twisted-pair cables are used in the LAN network, you can check the following tutorial.

Twisted-pair cabling

This tutorial explains how the twisted-pair cable works and how it is used to connect different networking
devices in a network.

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The TIA/EIA specifies standards for the twisted-pair cable. The first standards were released in 1991,
known as TIA/EIA 568. Since then, these standards have been continually revised to cover the latest
technologies and developments of the transmission media.

The TIA/EIA 568 divides the twisted-pair cable into several categories. The following table lists the most
common and popular categories of twisted-pair cable:

This cable consists of a core, cladding, buffer, and jacket. The core is made from thin strands of glass or
plastic that can carry data over a long distance. The core is wrapped in the cladding; the cladding is
wrapped in the buffer, and the buffer is wrapped in the jacket.

• Core carries the data signals in the form of light.

• Cladding reflects light back to the core.
• Buffer protects the light from leaking.
• The jacket protects the cable from physical damage.

Fiber optic cable is completely immune to EMI and RFI. This cable can transmit data over a long distance
at the highest speed. It can transmit data up to 40 kilometers at the speed of 100Gbps.

Fiber optic uses light to send data. It reflects light from one endpoint to another. Based on how many
beams of light are transmitted at a given time, there are two types of fiber optical cable; SMF and MMF.

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SMF (Single-mode fiber) optical cable

This cable carries only a single beam of light. This is more reliable and supports much higher bandwidth
and longer distances than the MMF cable. This cable uses a laser as the light source and transmits 1300
or 1550 nano-meter wavelengths of light.

MMF (multi-mode fiber) optical cable

This cable carries multiple beams of light. Because of multiple beams, this cable carries much more data
than the SMF cable. This cable is used for shorter distances. This cable uses an LED as the light source
and transmits 850 or 1300 nano-meter wavelengths of light.

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Apparatus (Components): RJ-45 connector, Climping Tool, Twisted pair Cable

Procedure: To do these practical following steps should be done:

1. Start by stripping off about 2 inches of the plastic jacket off the end of the cable. Be very careful at
this point, as to not nick or cut into the wires, which are inside. Doing so could alter the characteristics
of your cable, or even worse render is useless. Check the wires, one more time for nicks or cuts. If there
are any, just whack the whole end off, and start over.

2. Spread the wires apart, but be sure to hold onto the base of the jacket with your other hand. You do
not want the wires to become untwisted down inside the jacket. Category 5 cable must only have 1/2 of
an inch of 'untwisted' wire at the end; otherwise it will be 'out of spec'. At this point, you obviously have
ALOT more than 1/2 of an inch of un-twisted wire.

3. You have 2 end jacks, which must be installed on your cable. If you are using a pre-made cable, with
one of the ends whacked off, you only have one end to install - the crossed over end. Below are two
diagrams, which show how you need to arrange the cables for each type of cable end. Decide at this point
which end you are making and examine the associated picture below.