UTP Cable

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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. 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 five categories of wire.

Categories of Unshielded Twisted Pair
Type Use
Category 1 Voice Only (Telephone Wire)
Category 2 Data to 4 Mbps (LocalTalk)
Category 3 Data to 10 Mbps (Ethernet)
Category 4 Data to 20 Mbps (16 Mbps Token Ring)
Category 5 Data to 100 Mbps (Fast Ethernet)

Buy the best cable you can afford; most schools purchase Category 3 or Category 5. If you are designing a 10 Mbps Ethernet network and are considering the cost savings of buying Category 3 wire instead of Category 5, remember that the Category 5 cable will provide more "room to grow" as transmission technologies increase. Both Category 3 and Category 5 UTP have a maximum segment length of 100 meters. In Florida, Category 5 cable is required for retrofit grants. 10BaseT refers to the specifications for unshielded twisted pair cable (Category 3, 4, or 5) carrying Ethernet signals. Category 6 is relatively new and is used for gigabit connections.

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Fiber Optic Cable

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Fiber optic cabling consists of a center glass core surrounded by several layers of protective materials. 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.

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.

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.

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Coaxial Cable

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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 is 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 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 than screw, onto the cable.

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Networking Cabling

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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.

In the 1970s and 1980s, coaxial cable was the preferred LAN medium. But by the late 1980s, data-capable twisted-pair wiring emerged as the predominant network cabling scheme. While twisted-pair wire has cable distance limitations, a hierarchical wiring scheme, initially built around hubs (and more recently switches), overcomes those limitations. Workstations are attached to workgroup hubs/switches in nearby wiring closets and those hubs/switches are attached to wiring hubs/switches at centralized data centers via twisted-pair cable, or via fiber-optic cable over long distances.

Ethernet Cable Summary
Specification Cable Type Maximum length
10BaseT Unshielded Twisted Pair 100 meters
10Base2 Thin Coaxial 185 meters
10Base5 Thick Coaxial 500 meters
10BaseF Fiber Optic 2000 meters
100BaseT Unshielded Twisted Pair 100 meters
100BaseTX Unshielded Twisted Pair 220 meters

Today, there are a variety of standards that define cable and component specifications, including the configuration, implementation, performance, conformance, and verification of cabling systems. The most prominent standards are listed here:

United States TIA/EIA-568-A (Telecommunications Industry Association/Electronic Industries Association-568-A), defines how to design, build, and manage a structured wiring system. Note that the specification is also called the EIA/TIA-568 in some references. Refer to "TIA/EIA Structured Cabling Standards" for more information.

International ISO/IEC IS 11801 (International Organization for Standardization/International Engineering Consortium) defines generic cabling for customer premises. It is being used in Europe, Asia, and Africa. See ISO/IEC-11801 Cabling Standards.

Europe Cenelec EN 50173 was derived from ISO 11801 and defines generic cabling and open-market cabling components.

Canada CSA T529-Canadian Standards for Telecommunications Wiring Systems that closely follows the TIA/EIA-568 specifications.

Australia and New Zealand SAA/SNZ HB27:1996. This standard is based on the TIA TSB67 standard. It specifies field testing of balanced copper cabling and the methodology of specifying field tester accuracy

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Difference Public and Private IP

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A unique Internet Protocol (IP) address, known as a public IP address, is assigned to every computer that connects to the Internet. The IP addressing scheme makes it possible for computers to “find each other” online and exchange information. Within a private network, computers use addresses excluded by convention from use on the Internet.

The difference between a private IP address and a public IP address then, is that private IP addresses are reserved for private networks, and public IP addresses are reserved for the Internet.

The Internet Assigned Numbers Authority (IANA), a once-autonomous organization, now works within the purview of the Internet Corporation for Assigned Names and Numbers (ICANN). IANA is responsible for overseeing global allocation of IP numbers, among other related protocols. Within the range of publicly available IP addresses are specific, excluded ranges withheld for private network use. These private IP ranges are as follows:

A class ...

B class ...

C class …

Computers within a private network are each assigned a unique address in order to exchange files and share resources with one another. The network router, which routes information, will pass data back and forth among the connected computers, using the respective addresses. But how do computers on a private network connect to the Internet?

Assuming the network has Internet connectivity, the computer connected to the digital subscriber line (DSL) modem is assigned a public IP address by the Internet Service Provider (ISP). This single public IP address is used to identify the network on the Internet. Now the network’s router acts as a gatekeeper between the private network and the public Internet. Using a built-in Network Address Translator (NAT), the router passes requests to the Internet using the assigned public IP address. Returning data is routed back to the public IP address, with the router determining which private IP address requested the information. In essence, the private IP address is daisy-chained to the public IP address through processes in the router.

A public IP address can be static or dynamic. A static public IP address does not change and is used primarily for hosting webpages or services on the Internet. Some gamers also prefer static IPs for interactive gaming. A dynamic public IP address is chosen from a pool of available addresses and changes each time one connects to the Internet. Most people have a dynamic public IP address, as it is the standard type of public IP address assigned when purchasing Internet connectivity.

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