Four bits are used for packed sequence numbering in a sliding window protocol…
2014
Four bits are used for packed sequence numbering in a sliding window protocol used in a computer network. What is the maximum window size ?
- A.
4
- B.
8
- C.
15
- D.
16
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Correct answer: C
Answer: 15
Explanation: With 4 bits for sequence numbering, there are 2^4 = 16 distinct sequence numbers (0 through 15).
For the Go-Back-N sliding window protocol, the maximum window size must be at most 2^k - 1 to avoid ambiguity between new and old frames. Calculating this gives 2^4 - 1 = 15.
Note: For Selective Repeat, the maximum safe window size is 2^{k-1} = 8 for k=4, which is a different constraint. The question is using the standard sliding window interpretation that yields 15.