Networking Quiz Questions and Answers

Questions and Answers

Can you help me fix this quiz? This is a short quiz in Networking class I submitted already. However, the grade came out very bad you can see the grade report at the end of the page. But my professor still gave me 1 more chance to submit it again to get higher score. 

Question 1: The source port number and destination port number are included in the TCP header only, not in the UDP header.

Answer: False

Question 2: Both UDP and TCP provide error detection service

Answer: True

Question 3: If a UDP segment has its length field valued 250 bytes, it mean than there are 250 bytes payload data (application data)

Answer: False

Question 4: TCP applies fast retransmit to a segment when the segment's timer expires.

Answer: False

Question 5: Over a TCP connection, suppose host A sends two segments to host B. Host B will send an acknowledgement (ACK) to A whenever it receives a segment from A. If the first ACK is lost, but the second ACK arrives before the timer set on the first segment expires, then host A will not retransmit the first segment

Answer: True

Question 6: Suppose host A sends host B one segment with sequence number 38 and it contains 4 bytes of data. Then in this same segment the acknowledgement number must be 42

Answer: True

Question 7: If a TCP segment contains 5 at its rwnd field (receiving window), that means the receiver should not send more than 5 segments at one time for the purpose of flow control.

Answer: True

Question 8: Which of the following application layer protocol using TCP?

Answer: HTTP

Question 9: Suppose you have the following two data sequences: 1101110101100110, and 0101010101010011. What is the value you should put in the checksum field if those are the only data you have

Answer: 1100110101000101

Question 10: Which of the following service is not provided by TCP?

Answer: identify end hosts

Question 11: The following questions are based on the condition described below:

Suppose Host A sends four TCP segments to Host B over a TCP connection. The first segment has sequence number 0; the second has sequence number 120, the third has sequence number 170 and the last one has sequence number 245. Assume sequence number used by B starts at 0 and the messages sent from B to A contains 10 bytes of data each.  

How much data is in the last segment?

Answer: cannot determine.

Question 12: Suppose the window size is 1. That is, A will wait for an ACK for its last sent segment before it sends another. Assume all four segments arrives B and all four ACKs sent back to A are received successfully. What is the acknowledge number of the third ACK sent back from B to A?  

Answer: 245

Question 13: Suppose that the first and second segments are received by B and the ACK of those two segments sent from B is received by A.  If the third segment A sends to B get lost but the last segment arrives at B. In the next acknowledgment that Host B sends to Host A, what will be the sequence number and acknowledgment number, respectively?

Answer: 30, 245

Question 14: If all segments are received by Host B, and the last segment contains 80 bytes of data, what is the sequence number and acknowledgment number contained in the last ACK message sent from B to A, respectively?

Answer: 30, 325

Question 15: If the second segment arrives before the first segment, what is the acknowledgment number in the first acknowledgment segment sent from B to A?

Answer: 10

Question 16: If all four segments arrives B, the first three acknowledge segments sent by B to A were lost, but the last ACK segment sent by B to A arrives A before the timer expires. Host A have to retransmit all three segments because it does not get ACK confirmations on those segments from B.  

Answer: True

Question 17: Consider the following Figure. Assuming TCP Reno is the protocol experiencing the behaviour shown below, answer the questions.

At the 19th transmission round, what happened?

Answer: packet loss is detected by timeout.

Question 18: What is the value of thresh at the 7th transmission round?

Answer: 19

Question 19: What is the value of thresh at the 18th transmission round?

Answer:  8

Question 20: During what transmission round is the 60th segment sent?

Answer: 6

Question 21: Assuming transmission is good for the 23rd and 24th round. But packet loss is detected after the 25th round by the receipt of a triple duplicate ACK, what will be the values of the congestion window size at the 26th round?

Answer: 1