GATE | GATE-IT-2004 | Question 80

In a data link protocol, the frame delimiter flag is given by 0111. Assuming that bit stuffing is employed, the transmitter sends the data sequence 01110110 as

(A) 01101011
(B) 011010110
(C) 011101100
(D) 0110101100


Answer: (D)

Explanation:

In the above question, if, in the data link layer bits stuffing is employed 
then bit stuffing is done using the flag delimiter. If there is a flag 
of n bits then we will compare the data sequence with the flag and for every 
n-1 bits matched found, a bit 0 is stuffed in the data sequence after the matched
sequence.

Thus using the above logic
Delimiter flag: 0111
Data sequence: 01110110
So, for a flag of 4 bits we will compare data sequence with pattern of 
3 bits i.e. 011.
0 1 1 0 1 0 1 1 0 0
In the above pattern the underlined bits are found matched, hence, 0 in italics 
is stuffed. Thus resulting in the data sequence as 0110101100 which is option D

This Explanation is contributed by Namita Singh.

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