Free The data link layer lessonsThe data link layer · Stage 1 · Flow control and reliability · Step 1
Stop-and-wait and why it is slow
See the simplest reliable protocol, and work out how little of a long link it uses. About 13 minutes.
Why does stop-and-wait waste so much of a long, fast link?
- AThe sender is idle for the whole round trip after each frame while waiting for the acknowledgement
- BIt retransmits every frame twice
- CIts frames have large headers
Show the answer
The sender is idle for the whole round trip after each frame while waiting for the acknowledgement. On a long link, that round trip is much longer than the time to send the frame.
4 questions on this idea
Short questions that apply the idea to new cases: trace it, work out a number, put steps in order. A wrong answer explains itself.
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