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Question

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. $16$

Answer given is $16$

Answer 1

Answer is 15.

As given, this is sliding window protocol so,in case consider Selective repeat:
 Sender window size = Receiver window size

and
Sender window size + Receiver window size = sequence numbering(2⁴)

Let window size is N.
N+N= 2⁴

N=2³
window size=8.
If we consider GBN then the max window size (16-1) =15

So Max window size =15

Comments

You are using Select Repeat ARQ. but for GBN it will be

Sender window size $2^{m}-1$

m is number of bits.

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see the question, it is asking for a sliding window protocol

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So, GBN is not sliding window protocol??

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:D thanks.