Computer Networks · topic
Single and two-dimensional parity, the Internet checksum with end-around carry, Hamming distance for detection and correction, Hamming check-bit count, and CRC: mod-2 long division worked bit by bit, the receiver check, and exactly which error patterns a generator is guaranteed to catch.
Noise, interference and faulty hardware flip bits. A receiver that cannot tell a damaged frame from a good one will pass garbage upward. Error detection adds redundant bits computed from the data; the receiver recomputes them and compares.
The cyclic redundancy check is the error-detecting code used in the trailer of almost every link-layer frame: Ethernet's 32-bit frame check sequence (FCS) is a CRC, and so are the checks in Wi-Fi, HDLC and PPP.
One-page visual sheets for this topic, in the sheet library on the store. Previews are free; the full sheets come with the subject pack.
