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21. A computer receives a timestamp request from another

computer at 2:34:20 P.M. The value of the original timestamp is 52,453,000. If the sender clock is 5 ms slow, what is the oneway time?

original timestamp = 52453000 milliseconds

Receive timestamp = 2:34:20 P.M = ((14x3600) + (34x60)

+20) x 1000

= 52460000 milliseconds

Time difference = Receive timestamp - (Original timestamp + one way time) 5 5

= =

one-way time

one-way time

52460000 – (52453000 + one-way time) 7000 - one-way time = =

7000 – 5 6995

22. A computer sends a timestamp request to another computer. It receives the corresponding timestamp reply at 3:46:07 A.M. The values of the original timestamp, receive timestamp, and

transmit timestamp are 13,560,000, 13,562,000, and 13,564,300, respectively. What is the sending trip time? What is the receiving trip time? What is the round-trip time? What is the difference between the sender clock and the receiver clock?

Return time = 3:46:07 A.M.

Original timestamp = 13560000 milliseconds Receive timestamp = 13562000 milliseconds

Transmit timestamp = 13564300 milliseconds What is the sending trip time? Sending trip time

timestamp

= Receive timestamp - Original

= 13562000 - 13560000 = 2000 milliseconds

What is the receiving trip time? Return time

7) x 1000

= 3:46:07 A.M. = ((3x3600) + (46x60) +

= 13567000 milliseconds

Receiving trip time

= Return time - Transmit timestamp

= 13567000 - 13564300 = 2700 milliseconds

What is the round-trip time? RTT = Sending trip time + Receiving trip time = 2000 + 2700

= 4700 milliseconds What is the difference between the sender clock and the receiver clock?

one way time = RTT/2 = 4700 /2

= 2350 milliseconds

Time difference = Receive timestamp - (Original timestamp + one way time)

= 13562000 – (13560000 +2350) = - 350 milliseconds