Reliable transport protocols must have at least a unique sequence number for each segment in the window. However, the protocol used can have additional requirements on the minimum unique sequence numbers beyond this requirement. What is the minimum number of unique sequence numbers required for the Go Back N protocol?
Try an answer before revealing the guidance below.
Key Concepts
- Send window W
- Receiver window of 1
- Cumulative ACK
- Sequence number wrap-around
Answer Approach
- Recall the Go-Back-N receiver only accepts the next in-order packet.
- Consider the case where a whole window is sent and all ACKs are lost.
- Find how many numbers are needed so a retransmission cannot look like new data.
Full Answer
Answer status: Verified against study notes. Revision notes, not an official marking scheme.
W + 1 unique sequence numbers for a send window of W packets.
Go-Back-N: sequence space ≥ W + 1Shortcuts: K concepts · A approach · F answer · R reviewed · B bookmark · ← / → previous / next