Free The transport layer lessonsThe transport layer · Stage 1 · Reliability and speed · Step 1
Reliable delivery
See how TCP uses acknowledgements, a timer that adapts to the round-trip time, and duplicate ACKs to recover from loss. About 14 minutes.
A TCP sender receives the same ACK number four times in a row. What does it conclude, and do?
- AA segment was probably lost; it retransmits it at once without waiting for the timer
- BNothing: it waits for the timer to expire
- CIt resets the connection
Show the answer
A segment was probably lost; it retransmits it at once without waiting for the timer. Three duplicate ACKs trigger fast retransmit.
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.
Answer them in your browserFree account, no card. Your progress is saved, and the idea comes back in a quick review later.
Sign up free to solve