What is Network Cabling?
What is Network Cabling?
Cable is one of the widely used mediums for information transmission between network devices. A network may have cables of the same type or a variety of cables may be used within the same network. The selection of cables for a network depends on the network’s size, protocol, cost, and the topology used. Keeping in mind the various properties of the cables, selection of appropriate cables is a must for the network to be successful.
For successful network cabling, we need to know the various properties and types of cables in details.
Coaxial Cable: Coaxial cable is composed of a copper conductor surrounded by a metal shield and a plastic insulator in-between the conductor and the shield. The metal shield provides resistance to interference from various sources like motors, computers, and fluorescent lights.
Coaxial cable is largely used due to its high resistance to external electrical interference and its support for accurate long distance signal connectivity. Coaxial cable is further categorized into thin (thinnet) and thick (thicknet) coaxial cables.
Thin or thinnet coaxial cable is widely used in linear bus networks, schools and colleges, etc. The specification for thin coaxial cable is referred by 10Base2, in which 2 represents the maximum length for a segment to be approximately 200 meters. However in practical situations the maximum segment length is 185 meters.
Thick coaxial cable is protected by an additional plastic cover to keep the moisture away from the central copper conductor and thus making it ideal for long distance network cabling. Thick coaxial cables are hard to bend due to the additional plastic cover and thus are difficult to install. The specification for thick coaxial cable is referred to by 10Base5, in which 5 represents the maximum length for a segment to be approximately 500 meters.
Connectors are used to join cables to other devices and to themselves. The widely used connector for coaxial cables is the BNC (Bayone-Neill-Concelman) connector with adaptors like a terminator, barrel connector and a T-connector. For efficient network cabling, the usage of a crimp BNC connector is recommended rather than the screw type connector.
Twisted Pair Cable: Twisted pair cable is categorized into shielded and unshielded twisted pair cables. Unshielded twisted pair cable (UTP) is widely used in network cabling and is popular in school, corporate, military, and medical, networks.
Different flavors of UTP cables are available from extremely high speed UTP to telephone grade UTP cables. The structure of UTP cables is composed of four pairs of wires within the jacket. To prevent crosstalk from electrical devices and the neighboring pairs, each pair is twisted with different number of twists per inch of wire. The quality of UTP cables depends on the tightness of the twists per foot, the tighter the twist, the higher the transmission rate and higher per foot cost. The wire pairs may also be separated by a spline inserted in the cable to further separate the wire pairs. Below are seven of the most commonly used categories of UTP standards that have been established by EIA/TIA (Electronic Industry Association/Telecommunication Industry Association)
Category 1: Includes Telephone wires with voice only
Category 2: Supports up to 4 Mbps of data rate for local talk
Category 3: Supports up to 10 Mbps of data rate for Ethernet
Category 4: Supports up to 20 Mbps of data rate for 16 Mbps Token Ring
Category 5: Supports up to 100 Mbps for Fast Ethernet
Category 5e: Supports up to 1000 Mbps for Gigabit Ethernet
Category 6: Supports up to 1000 Mbps for Gigabit Ethernet
Choosing the proper category for the particular need is of vital importance for the network cabling to be efficient and successful. Category 3 is used for most telephone connections. Category 5 is mostly used in older networks. Category 5e replaces category 5 for systems being installed currently. Not only the cost but the future expansion of the network must also be kept in mind while designing a network. Category 5e or 6 should be used to accommodate the addition of more devices, requiring higher data speeds in the future.
A plastic connector called RJ-45 (Registered Jack) connector is used for UTP cables. RJ-45 connectors are inserted only one way into the slot and are based on a standard borrowed from the telephone industry. This standard guides each wire to be associated with a particular pin in the connector.
Shielded Twisted Pair (STP) Cable is designed to overcome the weak resistance of UTP cables to outside interference and radio frequencies. An extra shield makes STP cable provide more resistance to the electrical interference and is commonly used in the older token ring topology.
Fiber Optic Cable: The most advanced and reliable cable is fiber optic cable. Fiber optic cable is made up of glass in the center surrounded by different layers of protective materials including cladding, coating, and aramid yarn. The outer layer includes an insulating jacket made of PVC or Teflon and Kevlar fiber to prevent the breakage and strengthen the cable. Light is used as a transmission medium instead of electronic signals and thus makes the fiber cable immune to any chance of electrical interference (EMI/RFI).
Transmitting signals at much higher speed (10-40 Gigabits) and longer distances (up to 40 Kilometers) makes fiber optic cable ideal for huge data transfer like interactive services and video conferencing. It is more difficult to terminate and modify fiber cables in network cabling than copper cables. This makes fiber optic cable more costly but depending on future network requirements, might end up costing less than having to replace copper cables later on. Fiber cabling is also more secure than copper cabling because it is very difficult to tap into the data. If tapped, there will be light leakage which would cause a cable failure. A barrel shaped connector called ST, with a rugged metal bayonet, is commonly used with fiber optic cable. A squared face SC connector is also popular, as well as a smaller LC version. A MT-RJ duplex “RJ” style design connector is also available.
Wireless LANs: As stated earlier, cable is the widely used medium for information transmission; however wireless networks also exist and have their own importance. Infrared light beams, lasers and radio signals are used as transmission mediums in wireless LANs. The connected devices in wireless LANs use an antenna or transceiver to send and receive information. Wireless networks are popular for small networks within the building or to adjacent buildings. However wireless communication is also possible at longer distances through microwave transmission, cellular phones or satellite.
Infrared communication may be scattered broadcast or line-of-sight communication. Infrared signals are sent in multiple directions in scattered infrared communication to bounce from wall and ceilings until they reach the receiver. However line-of-sight transmissions reach the receiver in direct line when there are no obstacles. An obstacle may block the transmission and cause the signal to have to be resent. Wireless LANs are slower than LANs using cables and are at risk to interference from electronic devices, bad weather, and provide poor security.
Some Guidelines for network cabling:
1. Protective materials should be used to protect the cables from any damage during transportation.
2. Usage of cable ties is recommended with copper cables and Velcro with fiber cables.
3. Test servers, switches, routers, etc before installation to avoid any problems while the cables are being installed.
4. Protective measures should be adopted to avoid injuries and any harmful effects to installer’s eyes from laser light sources for fiber cables.
5. For copper cables, power cables should be separated from data cables if possible to reduce error inducing crosstalk.
