Network Security Inteview Questions freshers on “Layers”.
1. What is the hamming distance between these 2 codes: 10010010 and 11011001?
a) 3
b) 4
c) 6
d) 2
Answer: b
Clarification: Hamming distance is number of dissimilar bits between 2 streams.
2. What is the hamming code for the data: 1001101?
a) 10011100101
b) 11010000101
c) 10001100101
d) 11111001011
Answer: a
Clarification:Find the 1st 2nd 4th and 8th bits using the hamming algorithm and thus proceed to get the hamming code.
3. 10010100101 is the code received. Find the error bit.
a) 7
b) 5
c) 2
d) 3
Answer: a
Clarification: Error occurs in bit 7 and can be found via hamming code.
4. The channel capacity is 100Mbps, the frame length is 10000 bits and the arrival rate is 5000 frames/sec. Calculate the mean time delay.
a) 400 µsec
b) 20 msec
c) 2000 µsec
d) 200 µsec
Answer: d
Clarification: T = 200 µsec from T= 1/(μC-λ).
5. Five channels, each with a 100-kHz bandwidth, are to be multiplexed together. What is the minimum bandwidth of the link if there is a need for a guard band of 10 kHz between the channels to prevent interference?
a) 4600 kHz
b) 500 kHz
c) 540 kHz
d) 580 kHz
Answer: c
Clarification: For five channels, we need at least four guard bands. This means that the required bandwidth is at least 5 × 100 + 4 × 10 = 540 kHz.
6. Find the checksum byte for the fallowing data words: 10110011, 10101011, 01011010, 11010101
a) 10001101
b) 01110010
c) 10110101
d) 01110010
Answer: a
Clarification: Do binary addition to compute the result.
7. Generate the CRC codeword for the message x3+1 using the generator polynomial x3+x+1.
a) 1001101
b) 1001001
c) 1001110
d) 1001111
Answer: c
Clarification: M(x) = 1001. G(x) = 1011.
x3*M(x) = 1001000.
On Dividing we get remainder as 110. Therefore, Codeword is 1001110.
8. Generate the CRC codeword for the data word 1101011011 using generator 10011. Also write both in the polynomial form.
a) 11010110110011
b) 11010110110110
c) 11010110111100
d) 11010110111110
Answer: d
Clarification: Solve using polynomial division and then appending the remainder to the divisor.