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Error
Control Schemes:
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used
to increase reliability. Complete reliability is not
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possible,
even internal circuits are not completely
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reliable
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must
deal with (at the data link layer) duplication,
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distortion,
deletion, and insertion of messages
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work
by increasing redundancy of message in some
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well-defined
way; consistency of received message is
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used
to assess the reliability of its information
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types
of error control schemes:
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forward
error control: uses error-correcting codes
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(such
as Reed-Solomon or Hamming codes) to send
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enough
information to allow receiver to detect and
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correct
errors
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feedback
error control: uses error-detecting codes
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(such
as parity bits, CRC) to allow receiver to detect
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but
not to correct errors. Requires retransmission for
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correction
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feedback
error control typically superior to forward
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error
control (but there are exceptions....)
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