Problem#1
Consider the CRC generator X4+X2+X+1.
(a) What is its binary representation?
=> 10111
(b) What is the maximum length k of the burst errors that can be detected when this CRC generator is used?
=> k=4 (Degree of the Generator Polynomial)
(c) Can any arbitrary k bit errors can be detected when this CRC generator is used?
=> No
Problem#2
Consider a 10kbps channel with around trip delay of 20msec. At what packet size the efficiency of the protocol will be at least 50% if the processing delays are ignored?
Efficiency will be 50% when the time to transmit the frame equals the round trip propagation delay. At the transmission rate of 10kbps, 200 bits takes 20msec.So minimum packet size required is 200 bits.
Problem#3
Consider the ABP protocol as shown on the attached sheet. The following table depicts its initial behavior. Complete this table for next two rounds of A getting and sending a message if the next event is time out at node B.
| Next Frame_A | Frame Expected_A | Node A Action | Node B Action | Next Frame_B | Frame Expected_B |
| 0 | 0 | A sends (0,1,A0) | B sends (0,1,B0) | 0 | 0 |
| 0 | 0 | A gets (0,1,B0) | A's message gets lost | 0 | 0 |
| 0 | 1 | B0 is delivered to NL | -- | 0 | 0 |
| 0 | 1 | A sends (0,1,A0) | -- | 0 | 0 |
| 0 | 1 | -- | B sends (0,1,B0) | 0 | 0 |
| 0 | 1 | A gets (0,1,B0) | B gets (0,0,A0) | 0 | 0 |
| 0 | 1 | A sends (0,0,A0) | A0 is delivered to NL | 1 | 1 |