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What is Network Cabling

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In this lesson, the various types of network media are described along with the tools used in day-to-day network operations.

Lesson Objectives

  1. Identify network cables and connectors.
  2. Categorize characteristics of connectors and cables.
  3. Identify the appropriate networking tools to use based on a given scenario.

Network Media

The network media determines the physical means by which data is propagated.

In general, copper cabling relies on electric pulses to transmit data, fiber optic cabling relies on light pulses to transmit data, and the air is the medium over which radio signals are propagated. In this topic, the four primary types of physical media are introduced. The reader will then learn the specific cabling standards for each type of physical media. 

Watch the video, Network Cabling – CompTIA A+ 220-801: 2.2 (10:27), to learn about the different types of cabling used on today’s networks.

Types of Media

There are four basic types of media used in a network:

  • Air – for wireless technologies.
  • Coaxial cable – has one central copper core surrounded by shielding. It uses either a BNC or F type connector.
  • Twisted-pair cable – uses eight individual copper wires with two twisted together to make four pairs of wires. Twisted-pair cable can be either:
    • Unshielded twisted pair (UTP) cable – eight wires are twisted in pairs to create a cancellation effect and minimize interference with the other pairs. It uses an RJ–45 connector. This is typically the type of cable we use in the United States.
    • Shielded twisted pair (STP) cable – uses the same cancellation techniques as UTP but adds a foil sheathing around all four pairs of wires to add an extra layer of protection. It uses a special STP connector that grounds the cable to the connecting device. Without this grounding, the extra shielding is negated.
  • Fiber optic cabling – uses modulated light to transmit data and so is not affected by electromagnetic interference. Fiber optic cabling is ideal for connections between buildings.

Network Cabling

There are basically five types of cabling systems. As each of these cabling systems is described, reference the summary information in Table 1, listing the speed, cable connectors, and maximum cable length.

  1. 10BASE2, or thinnet, uses a coaxial cable like the ones found connected to our television sets. This is known as an RG–6 and uses either BNC or F type connectors. 10BASE2 is specified to have a maximum cable length of 185 m and a maximum speed of 10 Mb per second.
  2. 10BASE5, or thicknet, uses a large thick coaxial cable and uses an AUI 15-pin D-shaped connector. 10BASE5 is specified to have a maximum cable length of 500 m and a maximum speed of 10 Mb per second.
  3. 10BASE-T is a legacy standard for a twisted-pair cable that uses an RJ45 connector.10BASE-T is specified to have a maximum cable length of 100 m and a maximum speed of 10 Mbps.
  4. 100BASE-TX and 1000BASE-T are still current network standards. They also specify using RJ45 connectors and a maximum cable length of 100 m. The maximum speeds are 100 Mbps and 1000 Mbps, respectively.
  5. The last group combines all the fiber optic cabling systems. Multi-mode cable has a maximum cable length of 2000 m and single-mode cable as a maximum cable length of 3000 m. Both can use ST, SC, or LC connectors.

Table 1: Video Standards and Bit Depth

Types of Cable Jackets

All cables have an outer jacket, as pictured in Figure 8, to protect the internal components. The two major types of cable jackets are characterized by their chemical composition:

  • Polyvinyl chloride (PVC) is the most common type sold for horizontal cabling and patch panel applications. It is inexpensive and best used in open air applications because of the toxic fumes it produces if burned.
  • A plenum is usually used for vertical cabling and inside walls and ceilings where there is no ventilation. It is more expensive to install because of its non-toxic and fire-resistant properties.

Figure 8: UTP Cable with Yellow Outer Jacket

Categories of Cable

Twisted-pair cabling is sold by categories defined by cable transmission properties.

  • Category 1 – Used for low voltage applications (doorbells, outdoor lighting)
  • Category 3 – Used for telephone wiring (voice only) and some 10 Mbps data connections, four-pair 100 Ohm UTP cables, 24 AWG solid copper wires, tested for attenuation and crosstalk (a signal transmitted on one circuit or channel that creates an undesired effect in another) through 16 MHz
  • Category 5 – Used for 100 Mbps data connections, 100 ohm UTP cables with 4 pairs, transmission up to 100 MHz, 24 AWG solid copper wires
  • Category 5e – Used for 100 Mbps and limited distance 1 Gbps data connections, e is an abbreviation for enhanced, 100 ohm UTP cables with 4 pairs, transmission up to 100 MHz, 24 AWG solid copper wires, more twists than Category 5 cable: extra twists improve performance by resisting interference, tighter twisting allows cables to resist separation and bunching during installation
  • Category 6 – Used for 1 Gbps and limited 10 Gbps data connections, 100 ohm UTP cables with 4 pairs, 4 pairs of 24 AWG copper wires, transmission up to 250 MHz, more twists than Category 5e cable: extra twists reduce crosstalk, resulting in a more reliable medium for 1000Base-T applications

All unshielded twisted pair cables use RJ45 connectors. The color of the outer jacket and the boot have no significance to the category or standards used.

  • The 568 wiring standard defines the categories and specifications used for Ethernet transmissions. Pair one is always blue, pair two is always orange, pair three is always green, and pair four is always brown. The order of the wires determines the scheme being used:
  • The 568A scheme puts the green pair on the left and splits the orange pair around the blue. This makes the wire order, from left to right: green/white, green, orange/white, blue, blue/white, orange, brown/white, brown.
  • The 568B scheme puts the orange pair on the left and splits the green pair around the blue. This makes the wire order, from left to right: orange/white, orange, green/white, blue, blue/white, orange, brown/white, brown; 568B is the standard used in the United States.

In Figure 9, the three types of cables used in networking are illustrated:

  • A straight through cable uses the 568B standard on both ends. It is used to connect, unlike devices. Examples would be computer-to-switch, computer-to-hub, switch-to-router or devices that use different decision-making processes, such as IP addressing or MAC addressing.
  • A crossover cable uses 568A ordering on one end and 568B ordering on the other. It is used to connect like devices. Examples would be switch-to-switch, computer-to-computer, computer-to-router, switch-to-hub, or devices that use the same decision-making process.
  • A rollover cable uses a 568B standard on one end and rolls or turns the cable over 180° on the other end. A rollover cable is used to connect a computer to a router or switch console port for programming.

Figure 9: RJ45 Pinouts

Watch the video Make a Category 5e Patch Cable (4:15) to see how to terminate and test an Ethernet UTP cable.

Voice & Dial-up

Voice and dial-up connections use the same twisted pair cable as Ethernet, but with the smaller RJ11 connector in place of the RJ45 connector. An RJ11 connector, seen in Figure 10, only uses 6 wires. RJ11 is the type of connector seen on phones, fax machines, and modems. DSL also uses an RJ11 connector.

Figure 10: RJ11 Connector

Network Connectors

Watch the video, Network Connector Types – CompTIA A+ 220-801: 2.1 (9:58), to learn about the connectors used in networks using different cables.

Coaxial Cables and Connectors

Coaxial cable is used for cable television and broadband cable modem installations. BNC connectors, seen in Figure 11, are used with the legacy Ethernet coaxial cabling options, such as thinnet and thicknet.

Figure 11: BNC Connectors

F Connectors, as seen in Figure 12, terminate RG-6 cables. F connectors are used with cable television and cable modem connections.

http://upload.wikimedia.org/wikipedia/commons/thumb/5/5b/F_Connector_Side.jpg/1024px-F_Connector_Side.jpg

Figure 12: F Connector

The RG-6 cable shown in Figure 13 is the coaxial cable used to connect audio/video equipment (TVS, DVD players, and satellite receivers).

Figure 13: RG-6 Cable

Fiber Optic Cable

Fiber optic cables are used in data communications. Data is represented using pulses of light. Fiber optic cables are more expensive than copper cables because of the complex manufacturing process required to create fiber optic cables. Figure 14 shows multiple fibers within a larger cable, and the larger cable is inside a yet larger cable.

http://upload.wikimedia.org/wikipedia/commons/0/02/Optical_fiber_cable.jpg

Figure 14: Fiber Optic Cable

Fiber Optic Cable Connectors

Fiber optic cables can use three different types of connectors:

  • ST – uses a BNC type connector to lock it on to the device. It is not commonly used as much today as in the past. See Figure 15.

http://upload.wikimedia.org/wikipedia/commons/thumb/2/2a/ST-optical-fiber-connector-hdr-0a.jpg/640px-ST-optical-fiber-connector-hdr-0a.jpg

Figure 15: ST Connectors

  • SC – the plug-in type of connector about the same size as an RJ45 connector. See Figure 16.

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Figure 16: SC Connectors

  • LC – a small form factor that allows two cables to fit in about the same space as an RJ45 connector. See Figure 17.

http://upload.wikimedia.org/wikipedia/commons/thumb/c/c0/LC-optical-fiber-connector-hdr-0a.jpg/800px-LC-optical-fiber-connector-hdr-0a.jpg

Figure 17: LC Connectors

All fiber optic cables require two cables to communicate, one to send and one to receive. The transmitter on one end is connected to the receiver on the other end.

Fiber optic cables are either single-mode or multi-mode:

  • Single-mode uses a laser light source, making it more expensive to implement. It uses a core of 8 to 10.5 µm and cladding of 125 µm. It has a maximum transmission distance of 80 km at 10 Gbps using commercially available transceivers. It is commonly used between buildings and in WANs.
  • Multi-mode uses an LED light source instead of a laser. Consequently, it has a maximum transmission distance of 2 km at 100 Mbps. There are both 50 and 62.5 µm core options with a 125 µm cladding. It is commonly used for intra-building connectivity and LAN backbones.

Network Tools

There are a great number of tools used in networking to make new cables and to troubleshoot defective cables. The video, Common Networking Tools (8:17), provides an overview of the tools discussed in this section.

  • A crimper is used to finalize the connection between an RJ45 or RJ11 connector and the cable. A crimper is pictured in Figure 18.

http://upload.wikimedia.org/wikipedia/commons/thumb/3/3e/Crimping-pliers-pro-RJ-0a.jpg/1024px-Crimping-pliers-pro-RJ-0a.jpg

Figure 18: Crimper

  • A punch down tool is used to connect a twisted-pair cable to a high volume punch down a block, usually known as a 110 punch down. See Figure 19.

Figure 19: Punch Down Tool

  • A cable tester is used to troubleshoot connectivity problems and test a cable to see if it meets standards. Different models give you the ability to test continuity, attenuation, near end crosstalk (NEXT), far end crosstalk (FEXT), the attenuation to crosstalk ratio (ACR), ping, and many other tests. See Figure 20.

File:Fluke Networks 10G kit.jpg

Figure 20: Cable Tester

  • A tone and probe is used to trace wires and check for breakage. See Figure 21.

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Figure 21: Tone and Probe

  • A multimeter is used to check AC/DC voltage, amperage, and continuity. See Figure 22.

File:Fluke87-V Multimeter.jpg

Figure 22: Multimeter

  • A loopback plug is used to test the internal workings of a network interface card (NIC). Figure 23 illustrates how to make an RJ45 loopback plug.

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Figure 23: RJ45 Loopback Plug

Summary

  • In this lesson, four types of network media used to create a network were described. The major copper cabling standards were described and their characteristics listed. PVC and Plenum cable jackets were described.
  • Category 1, 3, 5, 5e, and 6 UTP cable standards were explained. The 568A and 568B wiring schemes were illustrated. Straight through, crossover and rollover UTP cables were described.
  • The various connectors used for each type of network media were discussed. Single-mode and multi-mode fiber optic cables were defined and their characteristics contrasted.
  • The network tools used to make cables and troubleshoot defective cables were introduced.
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About Ahmad Faizan

Mr. Ahmed Faizan Sheikh, M.Sc. (USA), Research Fellow (USA), a member of IEEE & CIGRE, is a Fulbright Alumnus and earned his Master’s Degree in Electrical and Power Engineering from Kansas State University, USA.