DCN - Target paper

Time limit: 2 hours

Name

1. Why are subnet masks necessary in IP addressing?

To provide data encryption

To reduce the size of the IP address

To hide the internal network IP address from external networks

To distinguish between the network and host portions of an IP address

2. How does CSMA/CD manage data collision on an Ethernet network?

By avoiding collisions through dedicated connections

By encrypting data to prevent collisions

By detecting collisions and retransmitting data after a random delay

By allocating specific time slots for data transmission

3. Which device operates at the data link layer of the OSI model?

Router

Repeater

Switch

Hub

4. In bus topology, how are devices connected?

In a mesh

In a ring

Along a single backbone

Through a central hub

5. Given the IP address 192.168.1.20 with a subnet mask of 255.255.224.0, what is the network ID?

192.168.1.1

192.168.0.0

192.168.1.255

192.168.1.0

6. Given the IP address 192.168.14.139/22, what is the network address and subnet mask?

Network address: 192.168.12.0, Subnet mask: 255.255.252.0

Network address: 192.168.14.0, Subnet mask: 255.255.252.0

Network address: 192.168.14.0, Subnet mask: 255.255.255.0

Network address: 192.168.12.0, Subnet mask: 255.255.255.0

7. Why VLAN configuration beneficial for network security?

It decreases the speed of data transmission

It enables logical segmentation, reducing unauthorised access to sensitive data

It speeds up data transmission

It encrypts connections between devices

8. What does CSMA/CA stands for?

Carrier Sense Multiple Access with Collision Detection

Carrier Signal Management and Control Algorithm

Carrier Sense Multiple Access with Collision Avoidance

Carrier Sense Multiplexing Algorithm with Collision Avoidance

9. What does VLAN stand for?

Virtual Local Area Network

Variable Local Area Network

Wireless Local Area Network

Virtual Logical Access Network

10. What is the purpose of "preamble" in an ethernet frame?

To synchronise the receiver’s clock with the sender’s clock

To check for errors in the frame

To encapsulate the frame

To identify the protocols

11. Which of the following is a characteristic of a ring topology?

There is a single point of failure

Data travels one direction around the ring

Each device is connected to every other device on the same network

All devices are connected via a central hub

12. What CSMA/CD stand for?

Carrier Sense Multiple Access with Collision Avoidance

Circuit Switching Multiple Access with Collision Detection

Carrier Sense Multiple Access with Carrier Detection

Carrier Sense Multiple Access with Collision Detection

13. How does a switch differ from a hub?

A switch operates at the Transport Layer, while a sub operates at the Network Layer

A switch operates at the Network Layer, while a sub operates at the Physical Layer

Both the switch and hub operates at the Data Link Layer

A switch operates at the Data Link Layer, while a sub operates at the Physical Layer

14. How does packet switching improve network efficiency compared to circuit switching?

It reduces the number of devices needed on a network thus increasing the throughput

It allows multiple packets to share the same network paths dynamically

It provides a dedicated path for each connection

It provides a guaranteed bandwidth for each connection

15. What is the main function of the Physical Layer in the OSI model?

To provide error detection

Managing the end-to-end message delivery

To format data in the Application Layer

To define physical specification for network interfaces

16. What is a function of the Transport Layer in the OSI model?

To format data in the Application Layer

To manage multiplexing and demultiplexing

Manage routing

Finding the shortest paths for packets to transfer

17. What happens if a frame received with an unknown destination MAC address on a switch?

The frame is discarded

The frame is sent to all the ports except the one it arrived on

The switch requests the port number from the device which sent it

The switch waits for the correct MAC address

18. What is the function of the loopback IP address in a computer network?

It connects two devices within a network

It acts as a backup IP address for the device

It is used to forward packets within the LAN

It is used to test the network connectivity on a local machine

19. What type of address is used at the Data Link Layer to identity devices on a network?

IP address

Domain

MAC address

Port number

20. What is a MAC address?

A logical address that is used for routing

A protocol used for data transmission

A physical address used to identify devices on a local network

A address that belongs to the transport layer

21. What is NOT true about an IP address?

The IP address is used for routing

The IP address belongs to the network layer

Every device must have an IP address in-order to connect to the internet

An IP address is used by switches to forward packets in a LAN

22. Compress the following IPv6 address to its shortest form.

2001:0df8:0000:0000:06ee:0000:0000:0f11

23. Explain the concept of an Autonomous System (AS) and its significance in internetworking. How do Interior Gateway protocols (IGP) differ from Exterior Gateway Protocols (EGP)?

(Please note that this question is not automatically marked, a sample answer will be provided at the end.)

24. Referring to the following successful scenario of a new device added to a network requesting a DHCP IP address from a DHCP server in the network, compute the source IP address and the destination IP address of each message transfer. Provide all the answers in the dotted decimal format as IPv4 addresses

A:
B:

C:
D:

E:
F:

G:
H:

25. What is the role of authoritative DNS servers, and how do they fit into the overall DNS hierarchy?

(Please note that this question is not automatically marked, a sample answer will be provided at the end.)

26. A company has been assigned an IP block with the starting address 14.24.74.0/24, and needs to create subnets. Fill in the blanks with the correct information for each subnet.

i. For the subnet with 64 addresses:

a) Subnet address:
b) Prefix: /
c) Broadcast address:
d) Subnet mask:
e) First usable IP address:
f) Last usable IP address:

ii. For the subnet with 32 addresses:

a) Subnet address:
b) Prefix: /
c) Broadcast address:
d) Subnet mask:
e) First usable IP address:
f) Last usable IP address:

27. A client and server are communicating using TCP. The client sends three segments of data to the server. The first segment has a sequence number of 1000 and a payload of 500 bytes. The second segment has a payload of 400 bytes, and the third segment has a payload of 600 bytes.assuming a successful communication upto the last segment sent calculate the client side and server side sequence and acknowledgement numbers and fill the corresponding locations with the correct answers.

A:
B:
C:
D:
E:
F:
G:
H:
I:

28. Explain the difference between symmetric key cryptography and public key cryptography.

(Please note that this question is not automatically marked, a sample answer will be provided at the end.)

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DCN – Target paper

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