Computer Networks BSCS 5 Semester/Term

Class: BSCs 5th (R+S) Subject: IAP Exam: Mid Marks: 30 Time: 1.5 hr

Q.No.1: Write down an IP address for all interfaces at all hosts and subnets in the network. The IP addresses for

A and E are as given. You should assign IP addresses so that interfaces on the same network have the same

network-part of their IP address, also assign address to each host. Indicate the number of bits in the network-

part of this address. Use default mask for the operation and purchased address is 180.16.0.0/24. [10]

Q.2. Suppose we want to transmit the message 10011010 and protect it from error, the Generator 1101. [8]

a. Use polynomial long division to determine the message that should be transmitted.

b. Suppose the rightmost bit of the message is inverted due to noise on the transmission link. What is the

result of the receiver's CRC calculation? How does the receiver know that an error has occurred?

Q.3. In the figure, draw/design the virtual circuit tables for all the switches after each of the following

connections is established. Assuming that the sequence of connections is cumulative; that is, the first

connection is still up when the second connection is established, and so on. Also assume that the VCI

assignment always picks the lowest unused VCI on each link and also reuse if it gets free, starting with

0.

Clearly draw complete switch tables after establishing all the following connections: [8]

a. Host A

connect to

Host B.

b. Host C

connect to Host

D.

c. Host C connect

to Host E.

d. Host D connect

to Host B.

e. Host C

disconnected

connect to

Host D.

f. Host A connect

to Host E

[4]

Q.4.

a. Draw IP header frame format and clearly mention each field.

b. Draw a timeline diagram for the sliding window algorithm with SWS = RWS = 3 frames for the

following two situations. Use a timeout interval of about 2xRTT.

(a) Frame 4 is lost.

(b) Frames 4-6 are lost.

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