Direction: Frames of 1000 bits are sent over a 106 bps duplex link between two hosts. The propagation time is 25 ms. Frames are to be transmitted into this link to maximally pack them in transit (within the link).
-
Suppose that the sliding window protocol is used with the sender window size of 21, where 1 is the number of its identified in the earlier part and acknowledgments are always piggy backed. After sending 21 frames, what is the minimum time, the sender will have to wait before starting transmission of the next frame? (Identify the closest choice ignoring the frame processing time.)
-
- 16 ms
- 18 ms
- 20 ms
- 22 ms
- 16 ms
Correct Option: B
Time taken to send 10^6 bits = 1 s
Now, as 1 frame = 1000 bits
Time taken to send 2^5 frames = 32 ms
Also, Time taken for first frame to be acknowledged = 25 × 2 = 50 ms
Hence, the waiting time = 50 – 32 = 18 ms
