Term
| What is the purpose of the physical layer? |
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Definition
| The purpose of the physical layer is to encode binary digits that represent the data link later frames into signals and to transmit and receive these signals across the physical media such as copper wire, fiber cable, and wireless. |
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Term
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Definition
| copper cable, fiber cable, wireless. what physical layer information is transmitted over. |
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Term
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Definition
| voltage, light, or radio waves transmitted from one device to another via a physical medium. represents data link layer frames in binary digits. |
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Term
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Definition
- THe physical media and associate connectors
- A representation of bits on the media
- Encoding data and control information
- Transmitter and receiver circuitry on the network devices
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Term
| Types of cabling and associate signals |
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Definition
- Copper Cable- electrical pulses/voltage
- Fiber-optic cable- light pulses
- Wireless- radio transmission waves
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Term
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Definition
| marks ends and beginnings of frames |
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Term
| Four areas of Physical Layer Standards |
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Definition
- Physical and electrical properties of media
- mechanical properties of the connection
- bit representation by the signals (encoding)
- definitions of control information signals
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Term
| Three components of Layer 1 communication |
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Definition
- physical components
- encoding
- signaling
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Term
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Definition
| converts pulse of energy into a defined amount of time |
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Term
| Three variations of a signal that represent coded bits |
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Definition
- amplitude
- frequency
- phase
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Term
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Definition
| measure of variation in the signal |
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Term
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Definition
| samples the voltage level on the medium during a bit time |
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Term
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Definition
| looks for a change in voltage in the middle of a bit time |
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Term
| What are the two types of signaling methods? |
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Definition
- NRZ- nonreturn to zero
- manchester encoding
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Term
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Definition
| symbol that is a predefined small group of bits that represent a larger group of data bits |
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Term
| Four areas that code groupd improve performance on a higher speed network |
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Definition
- reducing the bit level error
- limiting effective energy transmitted into the media
- helping distinguish data bits from control bits
- providing better media error detection
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Term
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Definition
- data symbols
- control symbols
- invalid symbols
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Term
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Definition
| data sent down from the physical layer |
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Term
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Definition
| layer 1 patterns denoting the beginning and the end of a frame |
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Term
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Definition
| bit patterns not allowed on the media that can indicate frame error |
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Term
| Three different ways to analyze transfer speed |
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Definition
- theoretically as bandwidth
- practically as throughput
- qualitatively as goodput
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Term
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Definition
| capacity of a medium to carry data in a given amount of time |
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Term
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Definition
| actual transfer rate of data over the medium in a period of time |
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Term
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Definition
| transfer rate of actual useable data bits |
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Term
| factors influencing throughput |
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Definition
- amount of traffic
- type of traffic
- number of network devices encountered on network being measured
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Term
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Definition
- conducts electrical signals well
- travels in pulses of electricity
- easily distorted by radio waves and electromagnetic devices
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Term
unshielded twisted pair (UTP)
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Definition
- most common type of copper medium
- 8 wires twisted in 4 color coded pairs
- most common connector is RJ-45 which has more pins than a telephone jack
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Term
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Definition
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Term
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Definition
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Term
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Definition
| connects serial port to a console port |
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Term
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Definition
| single, coated copper wire center and an outer metal mesh that acts as a grounding circuit and an EMI shield to reduce interference |
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Term
| Two major safety risks of Copper media |
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Definition
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Term
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Definition
- uses light to send signals
- two kinds: single-mode and multimode
- glass core with cladding and shielding
- photodiodes interpret the light signal
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Term
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Definition
- uses laser as light source
- more xpensiv-e
- glass core 8-10 microns
- less dispersion of light
- distance: 100kms
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Term
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Definition
- uses LED light source
- 50+ micron core
- greater dispersion (loss of light)
- shorter distance up to 2km
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Term
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Definition
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Term
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Definition
- 802.11 is common protocol
- radio signals
- open areas best
- usually slower
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Term
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Definition
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Term
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Definition
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Term
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Definition
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Term
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Definition
| Global System for Mobile Communications (GSM) - cellphones |
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Term
| Three common fiber repair problems |
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Definition
1. misalignment
2. end gaps where fibers do not completly touch
3. poorly finished ends causing poor clarity |
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Term
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Definition
| Optical Time Domain Reflectometer- special fiber-optic test device |
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