Problem 1:10 Points An upper-layer packet is split into 10 frames, each of which has an 85% chance of arriving undamaged. If no error control is done by the data link protocol, how many times must the message be sent on average to get the entire thing through? Problem 2:10 Points The following character encoding is used in a data link protocol: A: 01000110 B: 10101011 FLAG: 01111110 ESC: 11110000 Show the bit sequence transmitted (in binary) for the five-character frame A ESC B ESC FLAG when each of the following framing methods is used: (a) Byte count (b) Flag bytes with byte stuffing Problem 3:15 Points (10, 5) 16-bit messages are transmitted using a Hamming code with 5 check bits to ensure that the receiver can detect and correct single-bit errors. Show the bit pattern transmitted for this message 1011,1101,1111, 0011 using odd parity. Now change the bit in the transmitted message counting from the left end that corresponds to the last digit of your jag number plus 6 (if the digit is zero, then it becomes six, or if the digit is nine, it becomes fifteen) and see whether the change is detected. Problem 4:10 Points (change font to Courier New for this problem) What is the remainder obtained by dividing xx+xx+x+x+1 by the generator polynomial x+1? Problem 5:20 Points (10, 10) (change font to Courier New for this problem) What is sent to the receiver if the message is: x1+x+x+x+x+x+x+x+1, and the divisor is x'+x'+x+1? Now add x to the message and show whether this bit change is detected. Problem 6:20 Points A 1024-bit message is sent that contains 992 data bits and 32 CRC bits. CRC is computed using the EEE 802 standardized, 32-degree CRC polynomial. For each of the following, explain whether the errors during message transmission will be detected by the receiver (a) There was a single-bit error (b) There were 2 isolated bit errors. (c) There were 5 isolated bit errors. (d) There were 28 isolated bit errors. (e) There was a 28-bit long burst error (0) There was a 39-bit long burst error Problem 7:10 Points The distance from earth to a distant planet is approximately 8.5 1012 m. What is the channel utilization if a stop-and-wait protocol is used for frame transmission on a 400 Mbps point-to-point link? Assume that the frame size is 256 KB and the speed of light is 3 x 10 m/s Problem 8: 10 Points In the previous problem, suppose a sliding window protocol is used instead. For what send window ze will the link utilization be 100%? You may ignore the protocol processing times at the and the receiver sender
