The document discusses various error control techniques used at the data link layer, including parity checks, checksums, and automatic repeat request (ARQ) protocols. It describes stop-and-wait ARQ, go-back-n ARQ, and selective reject ARQ. For example, stop-and-wait ARQ involves the sender transmitting a single frame and waiting for an acknowledgment before sending the next frame. Go-back-n ARQ allows the sender to transmit multiple frames before waiting for an acknowledgment.

1. Group members : Alisha Korpal Nancy Jain Nivia Jain Sharuti Jain

10. Even parity 1 1 0 0 1 1 1 1 1 0 0 1 1 1 1 1 1 0 0 1 1 1 1 Even Parity Generator (counts 1 in data) 1 Sender Receiver Parity checker Counts 1 in data + VRC) Odd parity Accept data Reject data

11. 11001010 10101010 11001100 11100011 01001111 11001010 10101010 11001100 11100011 11001010 10101010 11001100 11100011 01001111 Original data LRC

12. 10101001 subunit1 00111001 subunit 2 11100010 sum 00011101 Compliment of sum 10101001 00111001 00011101 data checksum Sender :

13. Receiver: 10101001 subunit1 00111001 subunit2 00011101 Checksum 11111111 sum 00000000 compliment No error

14. Sender: 1011 1011 0100 0000 1000 1011 0110 0000 110 1001000 1011

15. Receiver : 1011 1010 Note: Remainder is zero, no error 1001110 1011 0101 0000 1011 1011 0000 0000 000

20. Sender Receiver DATA ACK EOT DATA ACK

28. Sender Receiver DATA 0 ACK 1 DATA 2 DATA 1 AC K 2 error NAK retransmit DATA 2 AC K 3

30. retransmit Sender Receiver DATA 0 ACK 1 DATA 2 DATA 1 AC K 2 lost DATA 2 AC K 3 Time out

32. Sender Receiver DATA 0 ACK 1 DATA 1 DATA 1 AC K 2 ACK 2 retransmit DATA 2 AC K 4 lost