NETWORKING DEVICES

Network Cable types

Cables are commonly used to carry communication signals within LAN. 

Coaxial cable

Coaxial Cables

First invented in the 1880s, "coax" was best known as the kind of cable that connected television sets to home antennas. Coaxial cable is also a standard for 10Mbps Ethernet cables . When 10 Mbps Ethernet was most popular, during the 1980s and early 1990s, networks typically utilized one of two kinds of coax cable - thinnet(10BASE2 standard) or thicknet (10BASE5). These cables consist of an inner copper wire of varying thickness surrounded by insulation and other shielding. Their stiffness caused network administrators difficulty in installing and maintaining thinnet and thicknet.

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.

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.

Twisted Pair Cable

Twisted Pair Cables

Twisted pair eventually emerged during the 1990s as the leading cabling standard for Ethernet, starting with 10 Mbps (10BASE-T, also known as Category 3 or Cat3), later followed by improved versions for 100 Mbps (100BASE-TX, Cat5 and Cat5e) and successively higher speeds up to 10 Gbps (10GBASE-T). Ethernet twisted pair cables contain up to 8 wires wound together in pairs to minimize electromagnetic interference.

Two primary types of twisted pair cable industry standards are defined – Unshielded Twisted Pair (UTP) and Shielded Twisted Pair (STP). Modern Ethernet cables use UTP wiring due to its lower cost, while STP cabling can be found in some other types of networks such as FDDI.

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).

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. 

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).

Optical Fiber Cabling

Fiber Optics

Instead of insulated metal wires transmitting electrical signals, fiber optic network cables work using strands of glass and pulses of light. These network cables are bendable despite being made of glass. They have proven especially useful in 

wide area network (WANs) installations where long distance underground or outdoor cable runs are required and also in office buildings where a high volume of communication traffic is common.

Two primary types of fiber optic cable industry standards are defined – single-mode (100BaseBX standard) and multimode (100BaseSX standard). Long-distance telecommunications networks more commonly use single-mode for its relatively higher bandwidth capacity, while local networks typically use multimode instead due to its lower cost.

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).

1. Single Mode Fibre (SMF) uses a single ray of light to carry transmission over long distances.

2. 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

USB Cables

Most Universal Serial Bus (USB) cables connect a computer with a peripheral device (keyboard or mouse) rather than to another computer for networking. However, special adapters (sometimes called dongles ) also allow connecting an Ethernet cable to a USB port indirectly. USB cables feature twisted-pair wiring.

Serial and Parallel Cables

Because many PCs in the 1980s and early 1990s lacked Ethernet capability, and USB had not been developed yet, serial and parallel interfaces that are obsolete on modern computers were sometimes used for PC-to-PC networking. So-called null model cables , for example, connected the serial ports of two PCs enabling data transfers at speeds between 0.115 and 0.45 Mbps.

Crossover Cables

Null modem cables are one example of the category of crossover cables . A crossover cable joins two network devices of the same type, such as two PCs or two network switches .

The use of Ethernet crossover cables was especially common on older home networks years ago when connecting two PCs directly together. Externally, Ethernet crossover cables appear nearly identical to ordinary (sometimes also called straight-through), the only visible difference being the order of color-coded wires appearing on the cable's end connector. Manufacturers typically applied special distinguishing marks to their crossover cables for this reason. Nowadays, though, most home networks utilize routers that have built-in crossover capability, eliminating the need for these special cables.