Question

Computer Networks

Hi guys. Please can you assist me in answering these questions. I will greatly appreciate it.

1. Packets with sequence numbers 0, 1, 2, 3, 4 and 5 have all been sent to the receiver. The receiver has received packets with sequence numbers 0,1,3 and 4. In which protocol will packets with sequence numbers 2, 3 and 4 be resent?
a. Stop and wait
b. RDT3.0
c. Go-Back-N
d. Selective repeat
e. None of the above

2. A web server runs in Host A on port 80. The web server uses persistent connections. The web server receives requests form Host B and Host C. Which of the following is true regarding the socket or sockets through which data is received at Host A?
a. The segments will be directed to a socket that is identified by 4 properties or tuples
b. The segments from Host A and Host B will be directed to different sockets
c. Segments are directed to connection sockets which differ from the original socket used for TCP handshaking
d. A, B and C
e. None of the above

3. The TCP congestion protocol always attempts to use the most bandwidth, increases the amount of data transmitted until packet loss occurs. What term is used to describe this?
a. Congestion avoidance
b. Bandwidth probing
c. Available bit rate
d. Self-clocking
e. None of the above

4. Comparing the Go-Back-N (GBN) and Selective Repeat (SR) protocols. Assume a window size of 15. How many timers are needed for GBN?

5. With reference to explicit congestion notification congestion control, which bit notifies the sender that there is congestion on the network?
a. ECN
b. ECE
c. ACK
d. SEQ
e. None of the above

6. In which reliable data transfer protocol is the sequence number sent with the ACK as part of the arguments
a. RDT2.0
b. RDT2.1
c. RDT2.2
d. A, B & C
e. None of the above

7. Which of the following do the Go-Back-N and Selective Repeat protocols both make use of?
a. Sliding scale
b. Sliding window
c. Sliding sequences
d. Sliding packet
e. None of the above

Answer 1

answer 1 -

Selective repeat --
as in selective repeat on those packets are retransmitted which are lost

answer 2 --

Segments are directed to connection sockets which differ from the original socket used for TCP handshaking

as port 80 is used for web services so we can connect as many hosts we want and HTTP services use TCP protocol for three-way handshaking

answer 3 --

Congestion avoidance

TCP congestion protocol generally checks if there is congestion in the network or not if not then  data transfer will utilize the full bandwidth

answer 4 --

Go-Back-N (GBN)	Selective Repeat (SR)
sending window size is "N" which is 15 in this case	sending window size is "N" which is 15 in this case
receiving window size is 1 always	receiving window size is "N" which is 15 in this case
if the packet is lost the whole window will be retransmitted	the only lost packet will be retransmitted
it uses cumulative acknowledgment	it uses the independent acknowledgment

I have given the explanation first four questions please ask if you have any doubt
thank you