Alternating bit protocol

alternating bit protocol
(ABP) A simple data link layer protocol that retransmits lost or corrupted messages.
Messages are sent from transmitter A to receiver B. Assume that the channel from A to B is initialised and that there are no messages in transit. Each message contains a data part, a checksum, and a one-bit sequence number, i.e. a value that is 0 or 1.
When A sends a message, it sends it continuously, with the same sequence number, until it receives an acknowledgment (ACK) from B that contains the same sequence number. When that happens, A complements (flips) the sequence number and starts transmitting the next message.
When B receives a message from A, it checks the checksum. If the message is not corrupted B sends back an ACK with the same sequence number. If it is the first message with that sequence number then it is sent for processing. Subsequent messages with the same sequence bit are simply acknowledged. If the message is corrupted B sends back an negative/error acknowledgment (NAK). This is optional, as A will continue transmitting until it receives the correct ACK.
A treats corrupted ACK messages, and NAK messages in the same way. The simplest behaviour is to ignore them all and continue transmitting.


Read Also:

  • Alternating calculus

    alternating calculus alternating calculus al·ter·nat·ing calculus (ôl’tər-nā’tĭng, āl’-) n. A urinary calculus having successive layers of different composition. Also called combination calculus.

  • Alternating current

    an electric current that reverses direction at regular intervals, having a magnitude that varies continuously in sinusoidal manner. Abbreviation: ac. noun a continuous electric current that periodically reverses direction, usually sinusoidally AC Compare direct current alternating current (ôl’tər-nā’tĭng) An electric current that repeatedly changes its direction or strength, usually at a certain frequency or range […]

  • Alternating group

    the subgroup consisting of all even permutations, of the group of all permutations of a finite set.

  • Alternating hemiplegia

    alternating hemiplegia alternating hemiplegia n. Hemiplegia caused by a lesion on the opposite side of the brainstem, accompanied by an additional paralysis of a motor cranial nerve on the same side as the lesion. Also called crossed hemiplegia, stauroplegia.

Disclaimer: Alternating bit protocol definition / meaning should not be considered complete, up to date, and is not intended to be used in place of a visit, consultation, or advice of a legal, medical, or any other professional. All content on this website is for informational purposes only.