go-back-n

Question

If sender window size is 75 and we are using Go back -N protocol then what will be sequence number required and what is the value of N?
A. 0 to 75 and 76      B. 0 to 74 and 75
C. 0 to 75 and 74      D. 0 to 74 and 76

Answer 1

In Go back N, N is the sender's window size.

If window size is 75 means N= 75

Sender can send maximum of 75 packets which need 75 sequence no( unique sequence no to each packet), i.e, 0 to 74

Hence option B) is correct.

Comments

You're wrong.

None of the above is right.

Number of sequence numbers should be at least one greater than sender window size in GBN.

Thus 76 sequences will be needed (i.e 0-75)

And as you said it goes back N times that is the window size and that's 75

The answer should be 0 to 75 and 75

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for $75$ winddow size we need $8$ bits. so sequence number $0-255$

Answer 2

0 to N-1  is sender Sequence No and N is Window Size