CC7 Computer Networks 2021 PYQ NBU

 

UNIVERSITY OF NORTH BENGAL

B.Sc. Honours 3rd Semester Examination, 2021

CC7 - COMPUTER SCIENCE (33)

COMPUTER NETWORKS

GROUP - A

1. What is Topology?

A network topology is the physical and logical arrangement of nodes and connections in a network.

2. Expand OSI.

OSI stands for Open Systems Interconnection. The OSI model was developed by the International Organization for Standardization (ISO). It is a reference model for how applications can communicate over a network.

3. What is computer network?

A computer network is a set of nodes connected by communication links, that can exchange data and share resources with each other.

4. What is multiplexing?

It is the process in which multiple signals coming from multiple sources are combined and transmitted over a single communication/physical line.

5. What is the function of transmission media?

It is a communication channel that transmits information by physical path from the source to the receiver.

7. Expand ARQ.

ARQ stands for Automatic Repeat Request also known as Automatic Repeat Query.

ARQ is an error-control strategy used in a two-way communication system.

8. What is flow control?

In data communications, flow control is the process of managing the rate of data transmission between two nodes to prevent a fast sender from overwhelming a slow receiver.

GROUP - B

9. Discuss the advantages and disadvantages of mesh topology.

Advantages:-

1. Failure of one single device does not affect the network.
2. No traffic problem as there is a point to point links for every computer.
3. Fault identification is easy.
4. It provides high privacy and security.

Disadvantages:-

1. Installation and reconnection are difficult.
2. Bulk of wiring.
3. It is expensive, compared to other topologies.
4. There is high risk of redundant connection.
5. Power consumption of mesh topology is more than the other topologies.

11. Discuss different multiplexing techniques.

Multiplexing is a technique used in computer networks to transmit multiple signals over a shared communication channel. Here are some common multiplexing techniques:

1. Time Division Multiplexing (TDM) - TDM divides the channel into time slots, and each input stream gets allocated a specific time slot.
2. Frequency Division Multiplexing (FDM) - FDM divides the channel into frequency bands, and each input stream is assigned a unique frequency band.
3. Wavelength Division Multiplexing (WDM) - WDM is used in optical fiber communication, where multiple signals are sent simultaneously at different wavelengths of light.
4. Code Division Multiplexing (CDM) - CDM assigns a unique code to each user, allowing multiple users to transmit simultaneously on the same frequency.
5. Space Division Multiplexing (SDM) - SDM involves using multiple physical paths, such as different antennas or fiber optic cables, to transmit data simultaneously.

12. Discuss the function of network layer of OSI reference model.

The OSI (Open Systems Interconnection) reference model has seven layers, and the network layer is the third layer in the model. Here are the key functions of the network layer:

1. Logical Addressing - The network layer assigns logical addresses (ex-IP addresses in the case of the Internet) to devices in a network.
2. Routing - The network layer is responsible for determining the best path for data packets to travel from the source to the destination across multiple interconnected networks.
3. Packet Forwarding - Once the optimal route is determined, the network layer encapsulates data into packets and forwards them to the next network device along the path.
4. Fragmentation and Reassembly - The network layer handles packet fragmentation and reassembly. Breaks large data into smaller packets for transmission. At the destination, these packets are reassembled into the original data.
5. Error handling - The network layer can detect errors in data transmission and, in some cases, provide error-handling mechanisms.

13. Differentiate between Cat3 and Cat5 twisted cables.

Difference between Cat3 and Cat5 twisted cables are given below:

1. Data Transmission Capacity:

• Cat3 - Cat3 cables are designed for voice and data transmission at speeds up to 10 Mbps.
• Cat5- Cat5 cables support higher data transmission rates, typically up to 100 Mbps.

2. Bandwidth: 

• Cat3 - Cat3 cables have a limited bandwidth suitable for lower-speed applications.
• Cat5- Cat5 cables offer higher bandwidth, allowing for more robust and efficient data transmission.

3. Twisting and Insulation:

• Cat3 - Cat3 cables have fewer twists per inch compared to Cat5 cables. They are generally used for shorter-distance installations.
• Cat5 - Cat5 cables have more twists per inch. It is suitable for longer-distance transmissions and higher-speed applications.

4. Use Cases:

• Cat3 - Cat3 cables are becoming less common in modern networking applications. They are suitable for voice communication and older Ethernet technologies.
• Cat5 - Cat5 cables are more versatile and are commonly used in various networking environments. They are suitable for both voice and data transmission, making them a standard choice for Ethernet installations.

5. Future Compatibility:

• Cat3 - Cat3 is less suitable for modern high speed networking requirements.
• Cat5 - While Cat5 cables are still used in some applications, they have been succeeded by newer standards like Cat5e (enhanced) and Cat6. which offer even higher data rates and improved performance.

GROUP - C

14. Discuss the applications of internet in different areas of the society.

Some of the applications of internet in different areas of the society:

1. Communication - The internet enables instant communication globally through email and messaging platforms, facilitating efficient and rapid exchange of information.

2. Education - The internet provides access to educational resources and facilitates online learning platforms, making education accessible to a global audience.

3. Healthcare - Internet technologies support telemedicine, allowing patients to consult with healthcare professionals remotely.

4. Business and Commerce - The internet has revolutionized commerce with online shopping and e-commerce platforms, providing a convenient way for businesses to reach consumers and vice versa.

5. Social Interaction - Platforms like Facebook, Twitter and Instagram connect people globally, enabling social interactions, information sharing and community building.

6. Information Access - The internet serves as a vast storehouse of information, accessible through search engines like Google.

7. Entertainment - Internet based streaming services (Netflix, Spotify, etc) allow users to access a variety of entertainment content, including movies, music and TV Shows.

8. Research and Development - Internet based collaboration tools enable researchers and professionals to collaborate on projects, share data, and conduct collaborative research globally.

9. Government Services - Governments use the internet to provide online services to citizens, such as tax filing, permit applications, and information dissemination.

10. Media and News - The internet allows real-time access to news and information through online news platforms, blogs and multimedia content.

15. Discuss LAN, MAN and WAN with the help of suitable examples.

LAN - A Local Area Network (LAN) is a computer network that interconnects computers within a limited area such as residence, school laboratory, university campus or office building. Example: Ethernet, Wi-Fi.

Example: Suppose a university campus has a LAN connecting all the buildings, departments and offices. Computers within this campus network can communicate with each other at high speeds, facilitating file-sharing, printing and collaborative work.

MAN - A Metropolitan Area Network (MAN) is a network that covers a larger geographic area by interconnecting a different LAN to form a larger network.

Example: Consider a city-wide cable network connecting various offices of a multinational corporation. This MAN allows for efficient communication and data sharing between branches of the company within the city.

WAN - Wide Area Network (WAN) is a network that spans a large geographic area, often a country, continent, or even worldwide, connecting multiple LANs and MANs.

Example: Imagine a company with offices in different countries interconnected through a WAN. This global network enables communication, data sharing, and collaboration among employees across the world. The internet itself is an example of a worldwide WAN.

16. What is ARQ? Explain stop and wait ARQ and go-back-n ARQ.

ARQ, or Automatic Repeat Request also known as Automatic Repeat Query, is a protocol used in communication networks to ensure that reliable delivery of data by automatically requesting re-transmission of lost or corrupted packets.

1. Stop and Wait ARQ:

• In Stop and Wait ARQ, the sender sends a single data frame and waits for an acknowledgement (ACK) from the receiver before sending the next frame.

Characteristics:

• Simple and easy to implement.
• It offers error and flows control.

2. Go-Back-N ARQ:

• In Go-Back-N ARQ, the sender is allowed to transmit multiple frames before receiving acknowledgements.
• The sender maintains a "window" of frames it can send without waiting for individual ACKs. If an ACK is not received for any frame in the window, all frames from that unacknowledged frame onward are retransmitted.

Characteristics:

• The sender can transmit multiple frames without waiting.
• Require a larger buffer at the sender to store unacknowledged frames.

17. Discuss connection-oriented virtual circuit switching with the help of examples.

Connection-oriented virtual circuit switching is a communication method in computer networks where a dedicated path, known as a "virtual circuit", is established between devices for the duration of their communication. This ensures reliable and ordered data transmission.

Example:

1. Telephone Call - When we make a call, a dedicated virtual circuit is established between your phone and the recipient's phone. Our conversation happens on this exclusive path, guaranteeing reliable and ordered communication, The path is released when the call ends.

2. Frame Relay Networks -  In Frame Relay, a wide-area network (WAN) technology, virtual circuits are set up between routers. These circuits ensure that data travels reliably and in order between these routers. The virtual circuit can be shared among multiple logical connections.

3. X.25 Networks - X.25 is an older packet-switching protocol, uses connection-oriented virtual circuits. When we send data over an X.25 network, a dedicated virtual circuit is created for our session, providing reliable and ordered data transfer.