Alternating Bit Protocol

**Prof. Dr. Sinsi** · 07-22-2012

* 1

&lt networking&gt (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

(2000-10-28)
English Related Words* 64 bit
* a bit
* a bit at sea
* a bit much
* a bit of
* a bit of skirt
* a bit off
* a bit thick
* a little bit
* a wee bit
* according to protocol
* added bit
* additional protocol (1970)
* address resolution protocol
* address resolution protocol (arp)

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07-22-2012	#1
Prof. Dr. Sinsi	Alternating Bit Protocol * 1&lt networking&gt (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, ie 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 (2000-10-28) English Related Words* 64 bit * a bit * a bit at sea * a bit much * a bit of * a bit of skirt * a bit off * a bit thick * a little bit * a wee bit * according to protocol * added bit * additional protocol (1970) * address resolution protocol * address resolution protocol (arp)