Hardware Cabling

The physical linkages responsible for carrying a company's data continue to be the most neglected components of the typical network�to the extent that nearly 70% of all network-related problems result from poor cabling.

In this third edition of a widely acclaimed resource, three networking experts share their extensive experience, teaching you the cabling skills you need to build a reliable, efficient, and cost-effective network cabling infrastructure. As you master these techniques, you'll learn to avoid common pitfalls and troubleshoot problems as quickly as they arise. Coverage includes:

Choosing the right cables and components for your network architecture and topology
Avoiding unnecessary and unexpected costs
Understanding the current limitations of data communications and network cabling
Understanding how laws and building codes constrain cabling
Understanding the function and importance of universal cabling standards
Determining when you have a cabling-related network problem
Assembling a complete cabling toolkit
Integrating voice and data on the same cable system
Setting up an infrastructure in which desktops, printers, copiers, and other nodes share cabling
Understanding issues of bandwidth, impedance, resistance, attenuation, crosstalk, capacitance, propagation, delay, and delay skew
Working effectively with USB and Firewire
Knowing when to discard legacy cabling and begin anew
Documenting your cabling
Creating an RFP and selecting a vendor

Types of Transmission

1. Baseband - Data bits are defined by discrete signal changes.
2. Broadband - Uses analog signals to divide the cable into several channels with each channel at its own frequency. Each channel can only transmit one direction.

Physical media

1. Twisted pair - Wire is twisted to minimize crosstalk interference. It may be shielded or unshielded.
   • UTP-Unshielded Twisted Pair. Normally UTP contains 8 wires or 4 pair. 100 meter maximum length. 4-100 Mbps speed.
   • STP-Shielded twisted pair. 100 meter maximum length. 16-155 Mbps speed. Lower electrical interference than UTP.
2. Coaxial - Two conductors separated by insulation such as TV 75 ohm cable. Maximum length of 185 to 500 meters.
   1. Thinnet - Thinnet uses a British Naval Connector (BNC) on each end. Thinnet is part of the RG-58 family of cable*. Maximum cable length is 185 meters. Transmission speed is 10Mbps. Thinnet cable should have 50 ohms impedance and its terminator has 50 ohms impedance. A T or barrel connector has no impedance.
   2. Thicknet - Half inch rigid cable. Maximum cable length is 500 meters. Transmission speed is 10Mbps. Expensive and is not commonly used. (RG-11 or RG-8). A vampire tap or piercing tap is used with a transceiver attached to connect computers to the cable. 100 connections may be made. The computer has an attachment unit interface (AUI) on its network card which is a 15 pin DB-15 connector. The computer is connected to the transceiver at the cable from its AUI on its network card using a drop cable.
   Coax cable types:
   • RG-58 /U - 50 ohm, with a solid copper wire core.
   • RG-58 A/U* - 50 ohm, with a stranded wire core.
   • RG-58 C/U* - Military version of RG-58 A/U.
   • RG-59 - 75 ohm, for broadband transmission such as cable TV.
   • RG-62 - 93 ohm, primarily used for ArcNet.
   • RG-6 - Used for satellite cable (if you want to run a cable to a satellite!).
   *Only these are part of the IEEE specification for ethernet networks.
3. Fiber-optic - Data is transmitted using light rather than electrons. Usually there are two fibers, one for each direction. Cable length of 2 Kilometers. Speed from 100Mbps to 2Gbps. This is the most expensive and most difficult to install, but is not subject to interference. Two types of cables are:
   1. Single mode cables for use with lasers.
   2. Multimode cables for use with Light Emitting Diode (LED) drivers.

Cable Standards

The Electronic Industries Association and Telecommunications Industries Association (EIA/TIA) defined a standard called EIA/TIA 568 which is a commercial building wiring standard for UTP cable. It defines transmission speed and twists per foot.

The maximum transmission length is 100 meters. This cable is susceptible to interference.

STP

Shielded twisted pair has a maximum cable length of 100 meters (328 feet). Data rate from 16 to 155 Mbps. Cables require special connectors for grounding but this cabling method resists electrical interference and is less susceptible to eavesdropping. Costs more than UTP or Thinnet, but not as much as Thicknet or Fiber-optic.

Terms

• Attenuation - Signal loss due to impedance.
• Bandwidth - Indicates the amount of data that can be sent in a time period. Measured in Mbps which is one million bits per second.
• Impedance - The amount of resistance to the transmission device.
• Interference - Electromagnetic Interference (EMI). Crosstalk - When wires pick up electromagnetic signals from nearby wires also carrying signals.
• Plenum - Space above a false ceiling in an office area where heat ducts and cables may be run. Plenum cabling is special fire resistant cabling required for use in these areas due to fire hazards.
• Shielding - Used to minimize interference.