4.2 - Error Control Flashcards
These kinds of errors (ex: mistake in typing a number) are usually controlled through the app or program (through app validation and error messages)
Human errors
These kinds of errors are controlled by the network hardware and software (ex: transmission error)
Network errors
Two categories of network errors:
- Corrupted data
- Lost data
Networks should be designed to ________, ________, and _________ both corrupted data and lost data
prevent…detect…correct
Introduced by equipment or natural disturbances, and it degrades the performance of a communication circuit
Noise
Noise manifests itself as:
- Extra bits
- Missing bits
- Bits that have been “flipped”
Sources of error:
- White Noise
- Impluse Noise
- Crosstalk
- Echo
- Attenuation
- Intermodulation Noise
Movement of electrons
Cause of white noise:
Sudden increases in electricity (e.g., lightning, surges)
Cause of impulse noise:
Multiplexer guardbands too small or wires too close together
Cause of crosstalk:
Poor connections
Cause of echo:
Gradual decrease in signal over distance
Cause of attenuation:
Signals from several circuits combine
Cause of intermodulation noise:
Techniques to prevent errors:
- Shielding
- Moving Cables
- Use of Repeaters/Amplifiers
______________ is the process of protecting wires by covering them with an insulating coating
Shielding
Shielding is one of the best ways to prevent:
- Impulse noise
- Crosstalk
- Intermodulation noise
______________ away from sources of noise can also reduce impulse noise, crosstalk, and intermodulation noise
Moving cables
For _____________ — avoiding lights and heavy machinery
impulse noise
For ___________ — physically separating the cables from other communication cables
crosstalk
For ______, ________ —- tune transmission equipment and redo connections
echoes….white noise
To avoid ______________, telephone circuits have repeaters or amplifiers spaced throughout their length
attentuation
The only way to do error detection is to send ______________ with each message
extra data
These error-detection data are added to each message by the ______________ layer of the sender on the basis of some mathematical calculations performed on the message
data link
The ___________ performs the same mathematical calculations on the message it receives and matches its results with the message
receiver
