Question

4) Consider the Rdt 2.0 protocol for reliable data transfer. Given the data (actual payload) determine checksums at sender and receiver side. Also, determine what type of response will be sent from receiver to sender. Explain? (20 points) Give values for sender checksum, receiver checksum and response?

Answer 1

solution:-

At the sender side:-

step 1. The given data unit is divide into segments of 8 bits as

11001010 , 01011100

step 2. Now all the segments are added and the result obtained as:

11001010 + 01011100=0100100110

step 3. here the result consist of 10 bits so extra 2 bits are wrapped around

00100110 + 01 = 00100111

step 4. Now 1's complement is taken and we get

11011000

thus checksum value= 11011000

At the receiver side :-

step 1. The received data t is divided into segments of 8 bits as

11011010, 10101100

step 2. add all the segments along with checksum of sender side i .e 11011000

11011010 + 10101100 + 11011000= 01001011110

step 3. since the result consist of 10 bits so it is wrapped around

01001011110 + 010 = 01100000

step 4. take 1's complement

10011111

since the result is not zero the receiver assumes that there is an error in the data.

The receiver will send a negative acknowledge , which requests the sender to send it again.