(SEM VI) THEORY EXAMINATION 2021-22 COMPUTER NETWORKS

COMPUTER NETWORKS (KCS-603)

B.Tech Semester VI – Theory Examination (2021–22) 

Computer Networks is a core subject in computer science and information technology that deals with the interconnection of computing devices for sharing data, resources, and services. A computer network enables communication between geographically distributed systems using standardized protocols, transmission media, and layered architectures. This subject builds the foundation for modern technologies such as the Internet, cloud computing, distributed systems, and mobile communication.

From the uploaded question paper, it is clearly visible that the examination focuses on network fundamentals, transmission media, network topologies, delays, OSI and TCP/IP models, flow control, error control, routing algorithms, IP addressing, subnetting, transport layer protocols, and application layer protocols. To score well, answers must be written in clear, logically connected paragraphs, explaining concepts in depth rather than listing short points.

SECTION A – BASIC NETWORKING CONCEPTS

(Based on Section A, Page-1) 

Transmission media in networking refers to the physical path through which data signals travel from sender to receiver. These media can be guided, such as twisted pair cables, coaxial cables, and optical fiber, or unguided, such as radio waves, microwaves, and infrared. The choice of transmission medium directly affects bandwidth, speed, noise immunity, and transmission distance.
 

Network topology describes the physical or logical arrangement of network devices and links. Common topologies include bus, star, ring, mesh, and hybrid. Topology selection impacts network reliability, scalability, and fault tolerance.
 

Transmission delay in flow control represents the time required to push all bits of a data packet onto the transmission medium. It depends on packet size and bandwidth and plays a significant role in determining protocol efficiency.
 

Round Trip Time (RTT) is the total time taken for a signal to travel from sender to receiver and back again. RTT is a critical performance parameter in congestion control, flow control, and TCP timeout calculations.
 

Logical addressing provides unique identification to devices in a network using IP addresses. It enables routing of packets across multiple interconnected networks, unlike physical addressing which works only within a local network.
 

A datagram in switching is a self-contained packet that carries complete addressing information. Each datagram is routed independently, which is a fundamental concept in packet-switched networks such as the Internet.
 

IP address classes A, B, C, and D define different address ranges used for unicast and multicast communication. These classes help in logical grouping and efficient address allocation.
 

The transport layer performs functions such as process-to-process delivery, segmentation and reassembly, flow control, and error control, ensuring reliable end-to-end communication.
 

The RST flag in the TCP header is used to reset a connection. It indicates an abnormal termination, such as when a packet is received for a non-existent connection.
 

HTTP (Hypertext Transfer Protocol) is an application layer protocol used for communication between web browsers and web servers. It follows a request–response model and is stateless in nature.
 

SECTION B – PHYSICAL, DATA LINK & NETWORK LAYER CONCEPTS

(Based on Section B, Page-1) 

In the physical layer of the ISO-OSI model, encoding techniques such as NRZ, Manchester, Differential Manchester, and Bipolar encoding are used to represent digital data as electrical signals. These encoding schemes help in synchronization, error detection, and noise reduction.
 

Networking commands such as ipconfig, netstat, ping, hostname, and tracert are diagnostic tools. They are used to configure network settings, check connectivity, trace packet paths, and diagnose network issues.
 

The STOP-AND-WAIT protocol is a simple flow control mechanism where the sender transmits one frame and waits for an acknowledgment before sending the next frame. Its main disadvantage is low channel utilization, especially in high-delay networks.
 

In Go-Back-N (GBN) protocol, the sender can transmit multiple frames before receiving acknowledgments. If every fifth packet is lost, retransmission starts from the lost packet, increasing total transmissions, as required in the numerical problem in the paper.
 

ICMP (Internet Control Message Protocol) operates at the network layer and is used for error reporting and diagnostic functions. ICMP messages help in detecting unreachable hosts, network congestion, and routing issues.
 

SECTION C – FLOW CONTROL AND SLIDING WINDOW

(Based on Section C, Page-1) 

The relationship between transmission delay and propagation delay determines the efficiency of the STOP-AND-WAIT protocol. To achieve at least 50% efficiency, the transmission delay must be comparable to the round-trip propagation delay.
 

In the sliding window protocol, window size and sequence numbers depend on transmission delay and propagation delay. Given values of Tt and Tp, the minimum window size is calculated to ensure continuous data flow without idle waiting.
 

ROUTING, ERROR CONTROL & MULTIPLE ACCESS

(Based on Page-2 of the paper) 

Distance Vector Routing (DVR) is a routing algorithm where each router maintains a table of distances to all destinations. Routers periodically exchange routing tables with neighbors and update routes using algorithms such as Bellman-Ford.
 

CRC (Cyclic Redundancy Check) is an error detection technique where data is divided by a generator polynomial. The remainder is appended to the data, allowing the receiver to detect transmission errors.

When data is transmitted across multiple routers, total transmission time depends on packet size, bandwidth, propagation delay, number of packets, and header overhead, as demonstrated in the numerical question.
 

CSMA/CD (Carrier Sense Multiple Access with Collision Detection) is a medium access control protocol used in Ethernet. Devices sense the channel before transmission and detect collisions during transmission, backing off before retrying.
 

IP ADDRESSING, OSI LAYERS & TRANSPORT PROTOCOLS
 

Subnetting divides a network into smaller sub-networks to improve routing efficiency and address utilization. Dividing the network 200.1.2.0 into five subnets requires careful calculation of subnet masks and address ranges.
 

The application layer provides services such as file transfer, email, and remote login, while the session layer manages session establishment, synchronization, and termination.
 

A detailed comparison of TCP and UDP highlights that TCP provides reliable, connection-oriented communication with flow and congestion control, whereas UDP provides faster, connectionless communication without reliability guarantees.
 

Application layer protocols such as FTP, SMTP, and DNS enable file transfer, email transmission, and domain name resolution respectively, forming the backbone of Internet services.
 

HOW TO WRITE COMPUTER NETWORKS ANSWERS IN THE EXAM
 

In Computer Networks, never write answers in short bullet points. Always begin with a definition, followed by working principles, examples, and significance. Numerical answers must include formulas, assumptions, and step-by-step calculations. Examiners focus heavily on conceptual clarity, protocol behavior, and logical explanation of networking mechanisms.