What is Network Cable? & Its Type

Network Cable

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.

Types of Cable

1. Twisted Pair 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 school networks.

Twisted-pair cable is the most common type of cabling you can see in today's LAN networks. A pair of wires forms a circuit that can transmit data. The pairs are twisted to provide protection against crosstalk, the noise generated by adjacent pairs.

When a wire is carrying a current, the current creates a magnetic field around the wire. This field can interfere with signals on nearby wires. To eliminate this, pairs of wires carry signals in opposite directions, so that the two magnetic fields also occur in opposite directions and cancel each other out. This process is known as cancellation. Two Types of Twisted Pairs are Shielded Twisted Pair (STP) and Unshielded Twisted Pair (UTP).

UTP cabling has different categories. Each category of UTP cabling was designed for a specific type of communication or transfer rate. The most popular categories in use today is 5, 5e and 6, which can reach transfer rates of over 1000 Mbps (1 Gbps).

2. 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.

The EIA/TIA (Electronic Industry Association/Telecommunication Industry Association) has established standards of UTP and rated six categories of wire (additional categories are emerging).

Unshielded twisted-pair (UTP) cable is the most common networking media. Unshielded twisted-pair (UTP) consists of four pairs of thin, copper wires covered in color-coded plastic insulation that are twisted together. The wire pairs are then covered with a plastic outer jacket. The connector used on a UTP cable is called a Registered Jack 45 (RJ-45) connector.

 UTP cables are of small diameter and it doesn’t need grounding. Since there is no shielding for UTP cabling, it relies only on the cancellation to avoid noise.

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. 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.

3. Shielded Twisted Pair

Shielded Twisted Pair (STP) Cable Although UTP cable is the least expensive cable, it may be susceptible to radio and electrical frequency interference (it should not be too close to electric motors, fluorescent lights, etc.). 

If you must place cable in environments with lots of potential interference, or if you must place cable in extremely sensitive environments that may be susceptible to the electrical current in the UTP, shielded twisted pair may be the solution. Shielded cables can also help to extend the maximum distance of the cables. Shielded twisted pair cable is available in three different configurations:

• Each pair of wires is individually shielded with foil.
• There is a foil or braid shield inside the jacket covering all wires (as a group).
• There is a shield around each individual pair, as well as around the entire group of wires (referred to as double shield twisted pair).

4. Coaxial Cable Connectors

The most common type of connector used with coaxial cables is the Bayone-Neill-Concelman (BNC) connector. 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 screw, onto the cable.

Coaxial cable looks similar to the cable used to carry TV signal. A solid-core copper wire runs down the middle of the cable. Around that solid-core copper wire is a layer of insulation, and covering that insulation is braided wire and metal foil, which shields against electromagnetic interference. A final layer of insulation covers the braided wire.

There are two types of coaxial cabling: thinnet and thicknet. Thinnet is a flexible coaxial cable about ¼ inch thick. Thinnet is used for short-distance. Thinnet connects directly to a workstation’s network adapter card using a British Naval Connector (BNC).

The maximum length of thinnet is 185 meters. Thicknet coaxial is thicker cable than thinnet. Thicknet cable is about ½ inch thick and can support data transfer over longer distances than thinnet. Thicknet has a maximum cable length of 500 meters and usually is used as a backbone to connect several smaller thinnet-based networks.

Coaxial cabling has a single copper conductor at its center. A plastic layer provides insulation between the center conductor and a braided metal shield. The metal shield helps to block any outside interference from fluorescent lights, motors, and other computers. 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 has been popular in school 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.

The bandwidth for coaxial cable is 10 Mbps (Mega bits per second).

These days Local Area Networks (LAN) use Twisted Pair cable. It is extremely difficult to find a live business network using coaxial cable.

5. Optical Fiber Cabling:

Optical Fiber cables use optical fibers that carry digital data signals in the form of modulated pulses of light. An optical fiber consists of an extremely thin cylinder of glass, called the core, surrounded by a concentric layer of glass, known as the cladding. There are two fibers per cable—one to transmit and one to receive. The core also can be an optical-quality clear plastic, and the cladding can be made up of gel that reflects signals back into the fiber to reduce signal loss.

There are two types of fiber optic cable: Single Mode Fibre (SMF) and Multi Mode Fibre (MMF).

• Single Mode Fibre (SMF) uses a single ray of light to carry transmission over long distances.
• Multi Mode Fibre (MMF) uses multiple rays of light simultaneously with each ray of light running at a different reflection angle to carry the transmission over short distances.

6. Cross-Over Cables:

If we want to connect two computers together with a straight-through cable, we can see that, the transmit pins will be connected to transmit pins and receive pins will be connected to receive pins. We will not be able to directly connect two computers or two switches together using straight through cables.

To connect two computers together without using a switch (or two switches directly), we need a crossover cable by switching wires 1 and 2 with wires 3 and 6 at one end of the cable. If we shift the pins, we can make sure that the transmit pins on Computer A will match with the receive pins on Computer B and the transmit pins on Computer B will match with the receive pins on Computer A.

7. Straight-Through cables

CAT 5 UTP cabling usually uses only four wires when sending and receiving information on the network. The four wires, which are used, are wires 1, 2, 3, and 6. When you configure the wire for the same pin at either end of the cable, this is known as a straight-through cable.

The wires 1 and 2 are used to transmit the data from the computer and 3 and 6 are used to receive data on the computer. The transmit wire on the computer matches with the receive wire on the switch. For the transmission of data to take place, the transmit pins on the computer should match with the receive pins on the switch and the transmit pins on the switch should match to receive pins on the computer.

Here we can see that the pins 1, 2, 3 and 6 on the computer matches with pins 1, 2, 3 and 6 on the switch. Hence we use the term Straight-through.

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