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 Selective Repeat protocol?
Try an answer before revealing the guidance below.
Key Concepts
- Send window W
- Receive window W
- Out-of-order buffering
- Sequence number wrap-around
Answer Approach
- Recall that the Selective Repeat receiver has its own window of W.
- Consider the receiver window sliding forward while the sender window has not.
- The two windows must not overlap in sequence space.
Full Answer
Answer status: Verified against study notes. Revision notes, not an official marking scheme.
2W unique sequence numbers (the window can be at most half the sequence space).
Selective Repeat: sequence space ≥ 2WShortcuts: K concepts · A approach · F answer · R reviewed · B bookmark · ← / → previous / next