FLOW AND ERROR CONTROL

STOP AND WAIT

ACK =acknowledgement

1. Sender sends a data packet to the receiver.
2. The sender needs to wait for the ACK after every frame it transmits
3. Sender stop and wait for ACK for the sent packet from the receiver.
4. Receiver receives and processes the data packet.
5. Receiver sends an ACK to the sender.
6. After receiving the ACK, sender sends the next data packet to the receive

ADVANTAGE OF STOP AND WAIT

It is simple and each frame is checked and ACK well

DISADVANTAGE OF STOP AND WAIT

only one frame can be send/transmission at a time

SLIDING WINDOW

THERE ARE TWO TYPE OF SLIDING WINDOW

1. GO BACK N
2. SELECTIVE REPEAT

GO BACK N

This the sliding window technique it allows data and control message to sent or transmitted continuously without waiting for ACK from the receiver.in the error detection at the receiving side the erroneous message is retransmitted

in which the sending process continues to send a number of frames specified by a window size even without receiving an ACK packet from the receiver.

ADVANTAGE OF GO BACK N

1. The sender can send many frames at a time
2. its efficency is more

DISADVANTAGE OF GO BACK N

1. Retransmission of many error-free packets following an erroneous packet
2. Buffer requirement

SELECTIVE REPEATE

Selective repeat is also known as a ARQ( Automatic Repeat reQuest). it is a data link layer.which uses sliding window kmethod for reliable delivery of data frames.

Here, only the erroneous or lost frames are retransmitted, while the good frames are received and buffered.

ADVANTAGE OF SELECTIVE REPEATE

Error detection is simple and requires much simper than the other techniques

DISADVANTAGE OF SELECTIVE REPEATE

If we have a channel a with high error rate, the information must be sent too frequently