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?
(A) (i) is false, but (ii) and (iii) are true
(B) (i) and (iii) are false, but (ii) is title
(C) (i) and (ii) are false, but (iii) is true
(D) (i), (ii) and (iii) are false
Answer: (B)
Explanation:
Time-out timer in TCP: One can’t use static timer used in data link layer (DLL), which is HOP to HOP connection, since nobody knows how many hops are there in the path form sender to receiver as it uses IP service and path may vary time to time. So, dynamic timers are used in TCP. Time-out timer should increase or decrease depending on traffic to avoid unnecessary congestion due to retransmissions.
There are three algorithms are for this purpose:
1. Basic algorithm
2. Jacobson’s algorithm
3. Karl’s modification.
Solution:
- The timeout value is set to the RTT (Round Trip Time) measured during TCP connection establishment for the entire duration of the connection.- FALSE
The timeout value can’t be fixed for entire duration as it will turn timer to static timer, we need dynamic timer for timeout.
- Appropriate RTT estimation algorithm is used to set the timeout value of a TCP connection.-TRUE
Yes, all three algorithm are appropriate RTT estimation algorithm used to set timeout value dynamically.
- Timeout value is set to twice the propagation delay from the sender to the receiver.-FALSE
This statement is false because, timeout value is set to twice the propagation delay in data link layer where, hop to hop distance is known, not in TCP layer.
This solution is contributed by Sandeep pandey.
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