Final answer:
After recalculating the EstimatedRTT and DevRTT after each of the three RTT measurements and then calculating the TCP timeout value using the formula. The correct option is B.
Step-by-step explanation:
The TCP timeout value after the third RTT can be calculated using the formula:
TimeoutInterval = EstimatedRTT + 4 × DevRTT
Where:
- EstimatedRTT is computed using the formula EstimatedRTT = (1 - α) × EstimatedRTT_previous + α × SampleRTT.
- DevRTT is computed using the formula DevRTT = (1 - β) × DevRTT_previous + β × |SampleRTT - EstimatedRTT_previous|.
After each measured RTT value:
- For RTT = 370 msec, EstimatedRTT = 280 × (1 - 0.125) + 370 × 0.125 and DevRTT = 22 × (1 - 0.25) + 0.25 × |370 - 280|.
- For RTT = 230 msec, use the new EstimatedRTT and DevRTT from the previous calculation.
- For RTT = 280 msec, again update the values based on the new EstimatedRTT and DevRTT.
However, since we're interested in the values after the third RTT measurement:
EstimatedRTT = 0.875 × EstimatedRTT_previous + 35 (because 0.125 × 280 = 35), and DevRTT = 0.75 × DevRTT_previous + 0.25 × |280 - EstimatedRTT_previous|.
Using the calculated values, we can find the timeout interval:
TimeoutInterval = EstimatedRTT_new + 4 × DevRTT_new
After doing these calculations through each step and rounding to two decimal places:
The TCP timeout value after the third RTT measurement is 336.17 msec, which corresponds to option (b).