negative acknowledgement


Also found in: Acronyms.

negative acknowledgement

[′neg·əd·iv ik′näl·ij·mənt]
(computer science)
In a data communications network, a control character returned from a receiving machine to a sending machine to indicate the presence of errors in the preceding block of data. Abbreviated NAK.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

negative acknowledgement

(character)
(NAK) The mnemonic for ASCII character 21.

Sometimes used as the response to receipt of a corrupted packet of information.

Opposite of acknowledgement.

negative acknowledgement

(communications)
(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.
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)
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