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  1. Introduction
  2. Network Model
  3. Topology
  4. Physical Media
  5. Wireless Media
  6. Network Card
  7. Modems
  8. Outside Connections
  9. Wide Area Network Connections
  10. Repeaters, Bridges, Routers
  11. Network Types
  12. Ethernet
  13. Token Ring
  14. ARCnet
  15. AppleTalk
  16. FDDI
  17. Architecture Comparisons
  18. Categories
  19. TCP/IP
  20. IPX/SPX
  21. NetBEUI
  22. AppleTalk
  23. SNA
  24. Others
  25. Suites and Network Layers
  26. Installing Drivers
  27. DNS
  28. Network Operating Systems
  29. Applications, mail, groupware, DBMS
  30. Backing up the network
  31. Troubleshooting
  32. Web, SNMP, admin, firewalls
  33. Networking Terms and Definitions
  34. Credits

Physical Media

  1. Twisted pair - Wire twisted to avoid 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 will have no impedance. Maximum thinnet nodes are 30 on a segment. One end of each cable is grounded.
    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. Maximum thicknet nodes are 100 on a segment. One end of each cable is grounded.
    The RG value for cable types refers to its size. Coax cable types:
    • RG-58 /U - 50 ohm, with a solid copper wire core for thin ethernet.
    • 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!).
    • RG-8 - 50 ohm thick ethernet.
    • RG-11 - 75 ohm thick ethernet.
    *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 has greater bandwidth and costs more. Injection laser diodes (ILD) work with single mode cable.
    2. Multimode cables for use with Light Emitting Diode (LED) drivers. All signals appear to arrive at the same time. P intrinsic N diodes or photodiodes are used to convert light to electric signals when using multimode.
    Types of fiber cable include:
    Fiber thickness (microns)Cladding thickness (microns)Mode

Physical Media Comparisons

MediaDistance(meters)SpeedApprox Cost/station
Fiber2000100Mbps-2Gbps$250 (multimode)

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. It defines transmission speed and twists per foot.

1NoneUsed for old telephone systems
310MpsThe minimum category for data networks
5100MpsCat 5 network cable, used by most networks today
6Data patch, Two pair with foil and braided shield
8Flat cable for under carpets with two twisted pair
9Plenum cable with two twisted pair. It is safe if you're having a fire.

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


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. Resists interference. Costs more than UTP or Thinnet, but not as much as Thicknet or Fiber-optic


  • 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.
  • (ILD) - Injection laser diodes work with single mode cable.
  • 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.