NPTEL Ethical Hacking Week 1 Assignment Answers 2024 (July-October)

Question 1

In which of the following penetration testing models, no information about the network is given to the tester?

a. White box model.
b. Black box model.
c. Gray box model.
d. Red box model.

Answer: b. Black box model.

Explanation: In a black box model, the tester has no prior knowledge about the network or system. This simulates an external hacking attempt where the attacker has to find vulnerabilities without any inside information.

Question 2

Which of the following statement(s) is/are true for a circuit-switched network?

a. A communication link may be shared by more than one connection.
b. A communication link is dedicated to a connection and cannot be shared with other connections.
c. The packet transfer delay between a pair of nodes may depend on the prevailing network traffic.
d. It is more efficient for bursty traffic.

Answer: b. A communication link is dedicated to a connection and cannot be shared with other connections.

Explanation: In a circuit-switched network, a dedicated communication path is established between two nodes for the duration of the connection. This path is not shared with other connections, ensuring a constant and predictable transmission rate.

Question 3

Which of the following statement(s) is/are false for virtual circuit-based packet transfer approach?

a. It is a connection-oriented approach, where a route is established prior to the transfer of packets.
b. The intermediate node can perform dynamic routing.
c. All the packets reach in order to the destination.
d. It is a true packet-switched network.

Answer: b. The intermediate node can perform dynamic routing.

Explanation: In a virtual circuit-based packet transfer approach, the route is predefined and does not change during the session, so dynamic routing by intermediate nodes is not typically performed. This ensures that packets follow the same path and usually arrive in order.

Question 4

A packet of size 2000 bytes is sent over a 50 kilo-bits-per-second (Kbps) point-to-point link whose propagation delay is 5 msec. The packet will reach the destination after ________ msec. (Assume 1K = 1000)

Answer: 325 milliseconds.

Explanation:

1. Convert the packet size to bits: $2000 \text{ bytes} \times 8 = 16000 \text{ bits}$.
2. Transmission time = $\frac{\text{Packet size}}{\text{Bandwidth}} = \frac{16000 \text{ bits}}{50 \text{ Kbps}} = 320 \text{ milliseconds}$.
3. Total time = Transmission time + Propagation delay = $320 \text{ ms} + 5 \text{ ms} = 325 \text{ ms}$.

Question 5

Which of the following OSI layers is responsible for end-to-end reliable data transfer?

a. Physical layer
b. Transport layer
c. Network layer
d. Datalink layer

Answer: b. Transport layer

Explanation: The transport layer (Layer 4 of the OSI model) is responsible for end-to-end communication and ensures reliable data transfer through error detection and correction mechanisms.

Question 6

Which of the following statement(s) is/are true for the IP address?

a. It uniquely identifies a network interface of a computer system.
b. It uniquely identifies a host in the network.
c. It indicates how many hardware ports are there in the computer system.
d. None of these.

Answer: b. It uniquely identifies a host in the network.

Explanation: An IP address uniquely identifies a host on a network, allowing for communication between devices.

Question 7

How many bits are used for IP address (in IPv4) and port number respectively?

a. 32, 8
b. 32, 16
c. 128, 8
d. 128, 16

Answer: b. 32, 16

Explanation: In IPv4, an IP address is 32 bits long, and a port number is 16 bits long.

Question 8

Which of the following is not a valid port number in TCP/IP?

a. 21
b. 80
c. 443
d. 8080
e. 80800

Answer: e. 80800

Explanation: Port numbers in TCP/IP are 16-bit integers, ranging from 0 to 65535. Therefore, 80800 is not a valid port number.

Question 9

If the IP header is 224 bits long, what will be the value of the "HLEN" field (in decimal)?

Answer: 7

Explanation: The HLEN (Header Length) field in an IP header specifies the length of the header in 32-bit words. $\frac{224 \text{ bits}}{32 \text{ bits per word}} = 7 \text{ words}$.

Question 10

The minimum size of the IP header required in an IP datagram is ________ bytes.

Answer: 20 bytes

Explanation: The minimum size of an IP header is 20 bytes, which includes the basic header fields without any optional fields.