Transport Layer

Question 21

On a TCP connection, current congestion window size is Congestion Window = 4 KB. The window size advertised by the receiver is Advertise Window = 6 KB. The last byte sent by the sender is LastByteSent = 10240 and the last byte acknowledged by the receiver is LastByteAcked = 8192. The current window size at the sender is  

• 2048 bytes
• 4096 bytes
• 6144 bytes
• 8192 bytes

Question 22

For a host machine that uses the token bucket algorithm for congestion control, the token bucket has a capacity of 1 megabyte and the maximum output rate is 20 megabytes per second. Tokens arrive at a rate to sustain output at a rate of 10 megabytes per second. The token bucket is currently full and the machine needs to send 12 megabytes of data. The minimum time required to transmit the data is _________________ seconds.

• 1.1
• 0.1
• 2.1
• 2.0

Question 23

Consider the following statements about the timeout value used in TCP. i. The timeout value is set to the RTT (Round Trip Time) measured during TCP connection establishment for the entire duration of the connection. ii. Appropriate RTT estimation algorithm is used to set the timeout value of a TCP connection. iii. Timeout value is set to twice the propagation delay from the sender to the receiver. Which of the following choices hold?

• (i) is false, but (ii) and (iii) are true
• (i) and (iii) are false, but (ii) is title
• (i) and (ii) are false, but (iii) is true
• (i), (ii) and (iii) are false

Question 24

Consider a TCP connection in a state where there are no outstanding ACKs. The sender sends two segments back to back. The sequence numbers of the first and second segments are 230 and 290 respectively. The first segment was lost, but the second segment was received correctly by the receiver. Let X be the amount of data carried in the first segment (in bytes), and Y be the ACK number sent by the receiver. The values of X and Y (in that order) are

• 60 and 290
• 230 and 291
• 60 and 231
• 60 and 230

Question 25

Which of the following statements are TRUE?
(S1) TCP handles both congestion and flow control
(S2) UDP handles congestion but not flow control
(S3) Fast retransmit deals with congestion but not flow control
(S4) Slow start mechanism deals with both congestion and flow control

• S1, S2 and S3 only
• S1 and S3 only
• S3 and S4 only
• S1, S3 and S4 only

Question 26

The three way handshake for TCP connection establishment is shown below. 

[caption width="800"] [/caption]

Which of the following statements are TRUE?
(S1) Loss of SYN + ACK from the server will not establish a connection
(S2) Loss of ACK from the client cannot establish the connection
(S3) The server moves LISTEN → SYN_RCVD → SYN_SENT → ESTABLISHED in the state machine on no packet loss 
(S4) The server moves LISTEN → SYN_RCVD → ESTABLISHED in the state machine on no packet loss.

• S2 and S3 only

• S1 and S4

• S1 and S3

• S2 and S4

Question 27

Consider the following statements regarding the slow start phase of the TCP congestion control algorithm. Note that cwnd stands for the TCP congestion window and MSS denotes the Maximum Segment Size.

1. The cwnd increase by 2 MSS on every successful acknowledgement.
2. The cwnd approximately doubles on every successful acknowledgedment.
3. The cwnd increase by 1 MSS every round trip time.
4. The cwnd approximately doubles every round trip time.

Which one of the following is correct?

• Only (ii) and (iii) are true
• Only (i) and (iii) are true
• Only (iv) is true
• Only (i) and (iv) are true

Question 28

Consider a long-lived TCP session with an end-to-end bandwidth of 1 Gbps (= 10⁹ bits-per-second). The session starts with a sequence number of 1234. The minimum time (in seconds, rounded to the closest integer) before this sequence number can be used again is _______ . Note - This was Numerical Type question.

• 34
• 4.30
• 43
• None of these

Question 29

Match the following:

• P-III, Q-IV, R-II, S-I
• P-II, Q-I, R-IV, S-III
• P-IV, Q-I, R-II, S-III
• P-IV, Q-I, R-III, S-II

Question 30

Which of the following layer of OSI Reference model is also called end-to-end layer ?

• Network layer
• Data layer
• Session layer
• transport layer