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physical media (medium)
Cabling & connectors used to interconnect the network devices.
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signal
Optical or electrical impulse on a physical medium for purposes of communication.
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encode
To change the energy levels transmitted over some networking medium to transmit bits over that medium.
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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)
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NRZ
Non-Return to Zero
Line code represented by one significant condition and 0s are represented by another.
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Manchester encoding
Line code in which each bit of data is signified by at least one voltage level transition.
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code group
Grouping of code that meets a certain specified condition for entering in that certain group.
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4B/5B
Encoding scheme
Uses 5-bit symbols or codes to represent 4 bits of data
Used in 100BASE-TX Ethernet
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kilobits
kbps
Unit of measurement of the number of times 1000 bits can be transmitted in 1 second.
1kbps = 1000bps
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megabits
Mbps
Unit of measurement of the number of times 1,000,000 bits can be transmitted in 1 second.
1 Mbps = 1,000,000 bps
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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.)
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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.
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attenuation
Loss of communication signal on the media.
Due to degradation of the energy wave over time.
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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.
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UTP
Unshielded Twisted-Pair cable
General type of cable, cable holds twisted pairs of copper wires and the cable itself having little shielding.
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RJ-45
A rectangular cabling connector with eight pins, often used with Ethernet cables.
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pinout
Defines which wires in a cable should connect to each pin on the connectors on both ends of a cable.
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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
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crossover cable
UTP cable used in Ethernet
Some pairs of twisted-pair wires are crossed at either ends of the RJ-45.
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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.
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coax / coaxial cable
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
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HFC
Hybrid Fiber-Coax
Network that incorporates both optical fiber along with coaxial cable to create a broadband network.
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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.
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fiber-optic cable
Physical medium that uses glass or plastic threads to transmit data.
Transmit data via light waves.
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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.
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