We looked at three protocols for providing reliable transport: Alternating Bit, Go-Back-N and Selective-Repeat. Which of these is likely to perform best in the presence of high error rates? Explain.
Try an answer before revealing the guidance below.
Key Concepts
- Retransmission
- Pipelining
- Go-Back-N
- Selective Repeat
- Receiver buffering
Answer Approach
- Compare how each protocol responds to one lost segment.
- Account for wasted retransmission.
- Account for pipelining and throughput.
Full Answer
Answer status: Draft answer (unofficial). Revision notes, not an official marking scheme.
Selective Repeat is generally best under high error rates. It can keep multiple packets in flight and retransmits only missing or damaged packets. Go-Back-N may retransmit a whole run after one loss, while Alternating Bit permits only one unacknowledged packet, limiting throughput. Selective Repeat requires more receiver buffering and bookkeeping.
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