Ch. 8 Key Terms

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Ch. 8 Key Terms
2011-12-12 17:54:29
Chapter Eight OSI Physical Layer Network Fundamentals CCNA Exploration Companion Guide

Chapter Eight OSI Physical Layer, Network Fundamentals, CCNA Exploration Companion Guide
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  1. physical media (medium)
    Cabling & connectors used to interconnect the network devices.
  2. signal
    Optical or electrical impulse on a physical medium for purposes of communication.
  3. encode
    To change the energy levels transmitted over some networking medium to transmit bits over that medium.
  4. bit time
    Time required to send a single bit over some transmission medium.

    • Calculated as 1/speed
    • (Speed = number of bits per second sent over the medium)
  5. NRZ
    Non-Return to Zero

    Line code represented by one significant condition and 0s are represented by another.
  6. Manchester encoding
    Line code in which each bit of data is signified by at least one voltage level transition.
  7. code group
    Grouping of code that meets a certain specified condition for entering in that certain group.
  8. 4B/5B
    Encoding scheme

    Uses 5-bit symbols or codes to represent 4 bits of data

    Used in 100BASE-TX Ethernet
  9. kilobits

    Unit of measurement of the number of times 1000 bits can be transmitted in 1 second.

    1kbps = 1000bps
  10. megabits

    Unit of measurement of the number of times 1,000,000 bits can be transmitted in 1 second.

    1 Mbps = 1,000,000 bps
  11. throughput
    Actual data transfer rate between two computers at some point in time.

    Impacted by the slowest-speed link used to send data between the two computers.

    (In addition to any other outside factors.)
  12. goodput
    Application-level throughput.

    Number of useful bits per unit of time from a certain source address to a certain destination.

    Excluding protocol overhead & retransmitted data packets.
  13. attenuation
    Loss of communication signal on the media.

    Due to degradation of the energy wave over time.
  14. noise
    General term referring to any energy signal on a transmission medium that is not part of the signal used to transmit data over that medium.
  15. UTP
    Unshielded Twisted-Pair cable

    General type of cable, cable holds twisted pairs of copper wires and the cable itself having little shielding.
  16. RJ-45
    A rectangular cabling connector with eight pins, often used with Ethernet cables.
  17. pinout
    Defines which wires in a cable should connect to each pin on the connectors on both ends of a cable.
  18. straight-through cable
    UtP cable pinout that specifies that the wire at pin 1 connects to pin 1 on the other end, pin 2 to pin 2, pin 3 to pin 3, etc.

    EX: connecting PC to hub or switch
  19. crossover cable
    UTP cable used in Ethernet

    Some pairs of twisted-pair wires are crossed at either ends of the RJ-45.
  20. rollover cable
    Cisco proprietary cable

    UTP pinout that specifies RJ-45 pinout connects pin 1 to pin 8, pin 2 to pin 7, pin 3 to pin 6, etc.

    Cisco console cables for routers and switches.
  21. coax / coaxial cable

    Consisting of a hollow outer cylindrical conductor that surrounds a single inner wire conductor.

    • Three different layers of material surrounding the inner conducting material:
    • the outer conductor
    • the insulator
    • the protective outer jacket
  22. HFC
    Hybrid Fiber-Coax

    Network that incorporates both optical fiber along with coaxial cable to create a broadband network.
  23. STP
    Shielded Twisted-Pair cable

    Type of network cable that includes twisted-pair wires, with shielding around each pair of wires,, as well as another shield around all wires in the cable.
  24. fiber-optic cable
    Physical medium that uses glass or plastic threads to transmit data.

    Transmit data via light waves.
  25. OTDR
    Certification method for fiber.

    Tool for testing fiber measuring the time to shine in one end and out the other noting the imperfections in between.