congestion control

Question

Consider the effect of using slow start on a line with 10 msec round trip time. The receiver window and the size of congestion window are set to 38 KB and 36 KB respectively. Sender side threshold is set to 18 KB. After 8 transmission a time-out occurs, after time out, the time taken to send first full window of 18 KB is____________ (in msec). Assume window size at the start of slow start phase is 2 KB.

Answer 1

Sender window size = min(congestion window, receiver window)

here, sender window = min(36KB,38KB)

window size at the start of slow start phase is 2 KB

initial threshold is set to 18 KB , after timeout threshold is set to 12KB

2|4|8|16|18|20|22|24(timeout)|2|4|8|12|14|16|18

total 14RTT is required.

total time = 14*10 = 140msec

Comments

but ans is given 70ms