The ATM protocol uses a cell with a 4-byte header, which is protected by an 8-bit checksum known as the HEC; this is a clever CRC which allows single-bit errors to be unambiguously detected (and therefore corrected), and multiple-bit errors to be detected as well. - http://cell-relay.indiana.edu/cell-relay/publications/software/CRC/32bitCRC.html - http://cell-relay.indiana.edu/cell-relay/publications/software/CRC/32bitCRC.tutorial.html - http://www.csc.gatech.edu/~copeland/6092/q_and_a/991001%20Error%20Detection.html CategorySoftware