What is the maximum window size in sliding window protocol used in a computer…

Concept

A sliding-window flow-control protocol lets the sender transmit several consecutively numbered frames before it must wait for an acknowledgment. The largest window the sender may open is bounded by how many distinct sequence numbers exist. With an n-bit sequence-number field there are 2n distinct sequence numbers, and the exact bound on window size then depends on the ARQ variant: Go-Back-N permits a maximum window of 2n − 1, while Selective-Repeat permits only half that many sequence numbers, so the receiver can always tell a new frame apart from a retransmitted old one.

Application

1. The item offers four candidate values — 4, 8, 15, 16 — for the maximum window size, but it does not itself state the width of the sequence-number field or which ARQ variant (Go-Back-N vs. Selective-Repeat) is intended.

2. The convention most commonly used for a generic “sliding window protocol” problem phrased exactly this way is a 4-bit sequence-number field under Go-Back-N: with n = 4, the sequence-number space has 24 = 16 values (0–15).

3. Applying the Go-Back-N bound to that space gives a maximum window size of 24 − 1 = 15.

Cross-check

Applying the same 4-bit field to Selective-Repeat instead gives half of 24 = 16, namely 8 — the other value some sources cite for this exact question. Because the item’s own text does not fix the bit-width or the ARQ variant, and no verified official answer key for this exact exam question could be located, the two conventions cannot be told apart with full certainty. A subject-matter expert should confirm the intended variant/bit-width (or the exam’s official key) before this item is published.