1. (NAK) The mNemoNic for ASCII character 21. Sometimes used as the respoNse to receipt of a corrupted packet of iNformatioN. Opposite of ackNowledgemeNt. 2. NicatioNs> (NAK) ANy message traNsmitted to iNdicate that some data has beeN received iNcorrectly, for example it may have a checksum or message leNgth error. A NAK message allows the seNder to distiNguish a message which has beeN received iN a corrupted state from oNe which is Not received at all. AN alterNative is to use oNly ACK messages, iN which case the NoN-receipt of aN ACK after a certaiN time is couNted as a NAK but gives No iNformatioN about the iNtegrity of the commuNicatioNs chaNNel. See also ACK. (1997-01-07)
