# Chandan Rajpurohit

An Artist With Technical Skills

1) For which of the following, the tester is provided only with partial information about a network?

a. White box model
b. Black box model
c. Gray box model
d. None of these

Solution: In the white box model, the tester has complete information about the network. In the black box model, the tester does not have any information about the network. Gray box testing is somewhere in between, where the tester is only provided with partial information about the network.

2) A 1000 byte packet is sent over a 50 kilo-bits-per-second (Kbps) point-to-point link whose propagation delay is 10 msec. The packet will reach the destination after __ msec.
(Assume 1K = 1000)

Solution: 50×1000 = 50000 bits per second can be transferred through the link.
1 bit can be sent in = (1/50000) sec
1000 byte or 8000 bits can be sent in 8000 / 50000 sec = 0.16 sec = 160 msec
Hence the packet will reach the destination after = 160 msec + 10 msec = 170 msec

3) Which of the following OSI layers are host-to-host layers?

a. Session layer
b. Transport layer
c. Network layer

Solution: The layers transport, session, presentation and application are host-to-host layers, while the remaining three are not.

4) How many bits are there in the IP address and port number?

a. 32, 16
b. 32, 8
c. 48, 16
d. 48, 8

Solution: IP address in IPv4 is 32 bits long, whereas port numbers in TCT or UDP are 16 bits long.

5) Which of the following is/are not true about a packet switched network?

a. A communication link can be shared by more than one connection.
b. A communication link is dedicated to a connection.
c. The packet transfer delay between a pair of nodes is more or less constant.
d. The packet transfer delay between a pair of nodes may vary with time.

Solution: In a circuit switched network, a communication link remains dedicated to a connection; however, in a packet switched network, communication links may be shared by more than one connection. Also, in a packet switched network, packets between the same source and destination may follow different paths, and hence the packet transfer delay can vary with time. Thus, options (b) and (c) are false.