The TCP round-trip time estimate is currently 500 msec and the following ACKs come in after an RTT equal to 350, 670, and 850 msec, respectively. a) What is the new estimated RTT (in msec)? Use α = 0.2. Show your detailed work b) For the same scenario as part a, if the starting RTT variation is 500msec, what is the final value of the timeout interval (in msec)? Use β = 0.35. Show your detailed work
The TCP round-trip time estimate is currently 500 msec and the following ACKs come in after an RTT equal to 350, 670, and 850 msec, respectively.
- a) What is the new estimated RTT (in msec)? Use α = 0.2. Show your detailed work
- b) For the same scenario as part a, if the starting RTT variation is 500msec, what is the final value of the timeout interval (in msec)? Use β = 0.35. Show your detailed work
Trending now
This is a popular solution!
Step by step
Solved in 3 steps with 16 images
Dear Wreiter are you sure about part b solution?
this is my solution and i have used it to solve it: Could you please double check it?
To calculate the final value of the TCP exponential backoff interval, we can use the formula:
RTO = current RTT + 4 * RTTVAR
RTO is the retransmission timeout
current RTT is the current estimate of RTT
RTTVAR is the current estimate of RTT variation.
Now, after each new sample RTT, we can update the estimate of RTTVAR using the formula:
RTTVAR = (1 - beta) * RTTVAR + beta * |difference|
where beta is a smoothing factor, and |difference| is the absolute difference between the current RTT and the latest sample RTT.
So for the given scenario, we have
beta = 0.35
current RTT = 578 msec
new sample RTT1 = 350 msec
new sample RTT2 = 670 msec
new sample RTT3 = 850 msec
Using the formula, we can calculate the new RTTVAR after each sample RTT:
New RTTVAR1 = (1 - 0.35) * 500 + 0.35 * |500 - 350| = 377.5 msec
New RTTVAR2 = (1 - 0.35) * 377.5 + 0.35 * |578 - 670| = 277.575 msec
New RTTVAR3 = (1 - 0.35) * 277.575 + 0.35 * |578 - 850| = 275.623 msec
Finally, we can use the updated value of RTTVAR to calculate the final value of RTO after the last sample RTT:
RTO = 578 + 4 * 275.623 = 1680.492 msec
Therefore, the final value of the TCP exponential backoff interval is 1680.492 msec.
by Bartleby Expert
