UG- S5 Computer Networks, First Internal Examination, August 2024

 Section A

Answer any 5 questions. Each question carries 2 marks.

1.      Explain WDM?

Wavelength Division Multiplexing (WDM) is a technology in fiber-optic communications that multiplexes multiple optical carrier signals on a single optical fiber by using different wavelengths (colors) of laser light. This allows for increased data transmission capacity by simultaneously transmitting multiple data streams over the same fiber.

2.      What  is transmission medium?

A transmission medium is a material substance that can propagate energy waves, such as light, sound, or electromagnetic waves. Common examples include optical fiber, copper wire, and air, each serving as a conduit for transmitting data in various communication systems.

3.      Explain UTP?

Unshielded Twisted Pair (UTP) is a type of cable used in networking that consists of pairs of wires twisted together to reduce electromagnetic interference. Commonly used in Ethernet networks, UTP cables are cost-effective and widely used for both residential and commercial applications.

4.    Define bit rate, baud rate.

Bit rate is defined as the transmission of a number of bits per second. Baud rate is defined as the number of signal units per second.

5.    Explain any two topologies in network.

Network topologies can be categorized as physical or logical. Physical topology refers to the physical medium's structure for data transmission, while logical topology refers to how data is transmitted between devices, regardless of their physical connection.

6.    Define the term transmission impairments.

  Transmission Impairment. • Signals travel through transmission media, which are not perfect. The imperfection causes signal impairment. This means that the signal at the beginning of the medium is not the same as the signal at the end of the medium.

                                                                                                    (5 x 2 =10 Marks)

Section B

Answer any 3 questions. Each question carries 5 marks.

7. Explain Fiber Optic Cable?

A fiber optic cable is a high-speed data transmission medium that uses light to transmit information. It consists of a core made of glass or plastic fibers, surrounded by a cladding layer that reflects light back into the core to minimize signal loss. Fiber optic cables offer several advantages over traditional copper cables, including higher bandwidth, faster transmission speeds, and longer transmission distances without significant signal degradation. They are immune to electromagnetic interference, making them ideal for environments with high electrical noise. Commonly used in telecommunications, internet connections, and data centers, fiber optic cables are critical for modern high-speed data networks.

8. Explain Multiplexing with suitable diagram?

Multiplexing is a technique used in telecommunications and data networks to combine multiple signals or data streams into one signal over a shared medium, optimizing the use of available bandwidth. There are several types of multiplexing, including Time Division Multiplexing (TDM), where each signal occupies a unique time slot within a repeating frame, and Frequency Division Multiplexing (FDM), where each signal is assigned a different frequency within the available bandwidth. This allows simultaneous transmission of multiple signals, enhancing the efficiency and capacity of communication systems.

9.      Describe TCP/IP protocol suite.

1. Application Layer

The application layer is the visible part of the computer network. It includes all the protocols, including interactive programs we use over the internet, such as web applications, email, etc.

2. Transport Layer

The transport layer is responsible for data packaging, including the construction and deconstruction of data into data packets so they can be transported across the network. The transport layer depends on the routing and delivery feature provided by the internet layer to send and receive data.

3. Internet Layer

The internet layer is responsible for sending, routing, and receiving data packets across the network.

4. Data Link Layer

The data link layer represents the physical properties of the network, NIC card, ethernet cables, fiber link, and all the hardware level elements that do the actual heavy lifting of transporting digital data from one point to another over the network.

 

10.  Which are the transmission modes used for  data communication? Explain with example.

There are three primary types of transmission modes based on the direction of exchange of information. The first is simplex, followed by half duplex, and finally full duplex. The Simplex transmission mode is used in computing networks when there is a single or one-way flow of information from sender to receiver.

                 (3 x 5 = 15 Marks)

 

Section C

Answer any 1 question. The question carries 15 marks

11. Explain Circuit Switched Networks and Datagram Networks?

Circuit Switched Networks

Circuit-switched networks operate by establishing a dedicated communication path between two endpoints for the entire duration of the communication session. This process involves three key phases:

1. Connection Establishment: Before any data can be transmitted, a dedicated path or circuit must be established between the sender and the receiver. This involves setting up a continuous sequence of physical or logical links through various intermediary switches.
2. Data Transfer: Once the circuit is established, data can be transmitted in a steady stream from the sender to the receiver. The dedicated path ensures that the bandwidth remains constant and unaffected by other users, providing a reliable and consistent connection.
3. Termination: After the communication session ends, the dedicated circuit is released, making the resources available for other users.

Circuit-switched networks are typical of traditional telephone systems, where a dedicated line is set up for a phone call, ensuring a consistent and high-quality connection. However, this can be inefficient, as the dedicated path remains reserved even when no data is being transmitted.

Datagram Networks

In contrast, datagram networks, as explained by Forouzan, use a connectionless communication model where data is divided into packets called datagrams. Each datagram contains all necessary routing information and is treated independently. Key characteristics include:

1. Independent Routing: Each datagram is routed independently through the network, possibly taking different paths to reach the destination. This means that packets may arrive out of order or take varying amounts of time to reach the recipient.
2. No Prior Setup: Unlike circuit-switched networks, there is no need to establish a dedicated path before data transfer. Datagram networks do not require a connection setup phase, making them more flexible and efficient in terms of resource utilization.
3. Best-Effort Delivery: Datagram networks operate on a best-effort delivery basis, meaning that the network does not guarantee packet delivery, order, or integrity. Higher-level protocols (such as TCP) are often used to ensure reliable communication.

 

12.  Explain ISO OSI reference model.

Physical Layer

The lowest layer of the OSI Model is concerned with electrically or optically transmitting raw unstructured data bits across the network from the physical layer of the sending device to the physical layer of the receiving device. It can include specifications such as voltages, pin layout, cabling, and radio frequencies. At the physical layer, one might find “physical” resources such as network hubs, cabling, repeaters, network adapters or modems.

Data Link Layer

At the data link layer, directly connected nodes are used to perform node-to-node data transfer where data is packaged into frames. The data link layer also corrects errors that may have occurred at the physical layer.

The data link layer encompasses two sub-layers of its own. The first, media access control (MAC), provides flow control and multiplexing for device transmissions over a network. The second, the logical link control (LLC), provides flow and error control over the physical medium as well as identifies line protocols.

Network Layer

The network layer is responsible for receiving frames from the data link layer, and delivering them to their intended destinations among based on the addresses contained inside the frame. The network layer finds the destination by using logical addresses, such as IP (internet protocol). At this layer, routers are a crucial component used to quite literally route information where it needs to go between networks.

Transport Layer

The transport layer manages the delivery and error checking of data packets. It regulates the size, sequencing, and ultimately the transfer of data between systems and hosts. One of the most common examples of the transport layer is TCP or the Transmission Control Protocol.

Session Layer

The session layer controls the conversations between different computers. A session or connection between machines is set up, managed, and termined at layer 5. Session layer services also include authentication and reconnections.

Presentation Layer

The presentation layer formats or translates data for the application layer based on the syntax or semantics that the application accepts. Because of this, it at times also called the syntax layer. This layer can also handle the encryption and decryption required by the application layer.

Application Layer

At this layer, both the end user and the application layer interact directly with the software application. This layer sees network services provided to end-user applications such as a web browser or Office 365. The application layer identifies communication partners, resource availability, and synchronizes communication.

 

                         (1 X 15 = 15 Marks)