Q21➡| Consider a subnet with 720 routers. If a three-level hierarchy is chosen, with eight clusters, each containing 9 regions of 10 routers, then the total number of entries in hierarchical table of each router is
i ➥ 27
ii ➥ 25
iii ➥ 72
iv ➥ 53
Q22➡| The Data Encryption Standard (DES) has a function consists of four steps. Which of the following is correct order of these four steps?
i ➥ an straight permutation, S-boxes, an XOR operation, an expansion permutation
ii ➥ a straight permutation, an XOR operation, S-boxes, an expansion permutation
iii ➥ an expansion permutation, S-boxes, an XOR operation, a straight permutation
iv ➥ an expansion permutation, an XOR operation, S-boxes, a straight permutation
Q23➡| Consider Euler’s Φ function given by Φ(n)=nÏ€p|n(1-(1/p)) Where p runs over all the primes dividing n. What is the value of Φ(35)?
i ➥ 3
ii ➥ 12
iii ➥ 6
iv ➥ 24
Q24➡| In hierarchical routing with 4800 routers, what region and cluster sizes should be chosen to minimize the size of the routing table for a three layer hierarchy ?
i ➥ 10 clusters, 24 regions and 20 routers
ii ➥ 12 clusters, 20 regions and 20 routers
iii ➥ 16 clusters, 12 regions and 25 routers
iv ➥15 clusters, 16 regions and 20 routers
Q25➡| An analog signal carries 4 bits in each signal unit. if 1000 signal units are sent per second, then baud rate and bit rate of the signal are___ and _____
21.(ii)
22.(ii)
23.(iv)
24.(iv)
25.(i)
Ans21-25
Ans22- an expansion permutation, S-boxes, an XOR operation, a straight permutation
Ans23- 24
Ans24-12 clusters, 20 regions and 20 routers
Ans25- 1000 bauds/sec, 4000 bps
Ans21-i
Ans22-iv
Ans23-
Ans24-iv
Ans25-ii
21) B
22) D
23)
24) D
25) C
21, I
22, I
23, ii
24, I
25, I