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CCN 2024 (NEP) Solved Question Paper Regular & Repeater

Computer Communications & Networks 2023 Regular Solved QP

I. Answer any ten of the following. (10x2=20)

1. Define protocol. Name the key elements of a protocol.

A protocol is a set of rules and conventions that govern the communication and interactions between systems, devices, or parties. Protocols ensure that data is transmitted accurately, efficiently, and securely across various networks or systems.

  • Syntax
  • Semantics
  • Error Control
  • Flow Control
2. List the layers of TCP/IP reference model.

The TCP/IP reference model consists of four layers that are essential for communication over the internet

  • Application Layer

  • Transport Layer

  • Internet Layer

  • Link Layer (Network Interface Layer)

3. Define transmission media.

Transmission media refers to the physical pathways or channels through which data is transmitted from one device to another in a communication system.

Or

Transmission media refers to the physical pathways or channels through which data, in the form of electrical signals, light pulses, or electromagnetic waves, travels from one device to another in a communication system.

4. Define multiplexing. List the types of multiplexing techniques.

Multiplexing is a technique used in telecommunications and data communication that allows multiple signals or data streams to be combined and transmitted over a single communication channel. 

  • Time Division Multiplexing (TDM)
  • Frequency Division Multiplexing (FDM)
  • Wavelength Division Multiplexing (WDM)
  • Code Division Multiplexing (CDM)
  • Statistical Time Division Multiplexing (STDM)
5. Name the two sub-layers of Data Link layer.
  1. Logical Link Control (LLC)
  2. Media Access Control (MAC) 
6. Define an error. List types of errors.

An error occurs when the received data is different from the transmitted data due to disturbances during transmission.

  • Single-Bit Error
  • Burst Error
  • Random Error
  • Systematic Error
7. State optimality principles of routing.

The optimality principle states that if a router X is on the optimal path from router A to router B, then the optimal path from X to B also lies along the same route.

8. Define flooding.

Flooding is a packet-forwarding technique in Content-Centric Networking (CCN) where a node forwards incoming packets to all its neighboring nodes, except the one it received the packet from.

9. Define Congestion.

Congestion occurs in a network when the demand for resources (such as bandwidth or buffer space) exceeds the available capacity, leading to performance degradation, packet loss, and increased delays.

10. List the elements of transport layer service.
  • Reliable Data Transfer
  • Connection Establishment and Termination
  • Flow Control
  • Error Detection and Correction
  • Multiplexing and Demultiplexing
  • Congestion Control
  • End-to-End Communication:
11. Define piggybacking.

Piggybacking is a technique used in data communication where the acknowledgment (ACK) of a received message is sent along with the data in the next transmission, rather than as a separate message.

12. Define www.
  • The World Wide Web (WWW) is a system of interlinked hypertext documents and multimedia content that can be accessed over the internet.
  • It allows users to browse websites using a web browser, enabling them to view text, images, videos, and interact with various online applications via hyperlinks and URLs.

II. Answer any FOUR of the following. (4x5=20)

13. Explain Radio transmission and Infrared transmission.

Radio Transmission:

Radio transmission uses electromagnetic waves in the radio frequency spectrum (typically between 3 kHz and 300 GHz) to transmit data over long distances. It is commonly used for wireless communication, such as in radio broadcasts, mobile networks, and Wi-Fi.

  • Range: Can cover large distances, from a few meters to thousands of kilometers, depending on frequency and power.
  • Uses: Broadcasting, mobile phones, Wi-Fi, satellite communication, GPS.
  • Advantages: Long-range, capable of penetrating through obstacles like buildings.
  • Disadvantages: Susceptible to interference and noise, bandwidth limitations.

Infrared Transmission:

Infrared transmission uses infrared light (typically in the range of 300 GHz to 400 THz) to transmit data over short distances. It is often used for communication between devices such as remote controls, wireless keyboards, and IR-based data transfer.

  • Range: Short-range, usually up to a few meters.
  • Uses: Remote controls, short-range data transfer (e.g., between mobile devices), IR sensors.
  • Advantages: Low interference with other communication systems, simple and low-cost.
  • Disadvantages: Limited range, requires line-of-sight between devices, affected by physical obstructions like walls.
14. Explain GO-Back N and selective repeal sliding window protocol.

GO-Back-N (GBN) Protocol

  1. Overview: GBN allows the sender to send multiple frames (up to a window size N) before needing acknowledgment. If an error occurs, all frames from the erroneous frame onward are retransmitted.

  2. Window Management: The sender maintains a sliding window of unacknowledged frames. It can transmit frames until the window is full but must wait for acknowledgments.

  3. Error Handling: If a frame is lost or erroneous, the sender must “go back” and resend that frame and all following frames, potentially leading to inefficiencies.

  4. Efficiency: GBN may result in higher retransmissions during poor network conditions, as it resends all subsequent frames after an error.

Selective Repeat (SR) Protocol

  1. Overview: SR allows for individual frame acknowledgment. The sender can send multiple frames (up to a window size N) but only retransmits specific erroneous frames rather than all subsequent ones.

  2. Window Management: Both the sender and receiver have a window size N, allowing for more efficient data handling and buffering of out-of-order frames.

  3. Error Handling: When a frame is received with an error, only that specific frame is retransmitted, while correctly received frames can be buffered and processed.

  4. Efficiency: SR is generally more efficient than GBN, as it minimizes the number of retransmissions and better utilizes bandwidth, especially in high-error environments.

15. Explain CRC with example.

Cyclic Redundancy Check (CRC):

CRC is an error-detecting code used to check for errors in data transmission or storage. It works by dividing the data by a fixed polynomial (generator) and appending the remainder (CRC) to the data. The receiver performs the same division; if the remainder is zero, the data is considered error-free.

Steps of CRC:

  1. Data Preparation: The original data is extended by appending zeros equal to the degree of the generator polynomial.

  2. Binary Division: The extended data is divided by the generator polynomial using binary division (XOR operation).

  3. CRC Code Generation: The remainder after division is the CRC value, which is added to the data before transmission.

  4. Verification: The receiver divides the received data by the same polynomial. If the remainder is zero, the data is error-free; otherwise, an error is detected.

Advantages:

  • Detects various errors (e.g., single-bit, burst errors).
  • Efficient in terms of implementation.

Disadvantages:

  • Only detects errors, not correct them.
  • Increases data size due to the appended CRC.

Example:

1101 (this is the result of division)
______
1011 | 1101011011000
1011 |
------
0110
1011
------
0011
1011
------
0000

At the end of this division, the remainder is 001.
16. Explain Link state routing algorithm.

The Link State Routing Algorithm is a type of routing protocol used in packet-switched networks for determining the best path for data transmission. It is commonly associated with the Open Shortest Path First (OSPF) protocol and the Intermediate System to Intermediate System (IS-IS) protocol. 

How Link State Routing Works:

  1. Initial Setup:
    • Each router in the network discovers its directly connected neighbors and measures the cost of the links to them (e.g., based on bandwidth or delay).
  2. Link State Advertisement (LSA):
    • Each router generates a Link State Advertisement (LSA), which contains information about its neighbors and link status.
    • These LSAs are broadcast to all other routers in the network to ensure that every router has the same view of the network’s topology.
  3. Link State Database (LSDB):
    • Once all routers receive LSAs, they update their own Link State Database (LSDB), which now contains a complete view of the network.
  4. Shortest Path Calculation:
    • Using the information in the LSDB, each router runs a Shortest Path First (SPF) algorithm (such as Dijkstra’s algorithm) to calculate the best path to every destination.
  5. Routing Table Construction:
    • Based on the SPF calculation, each router creates its routing table, which contains the shortest path to all possible destinations in the network.
  6. Periodic Updates:
    • If there is a change in the network topology (e.g., link failure or new router added), the affected router generates a new LSA, and all routers update their LSDBs and routing tables accordingly.

Advantages of Link State Routing:

  • Convergence Speed: Link State Routing converges quickly when there are topology changes because each router immediately updates its LSDB.
  • Scalability: More scalable for large networks due to its ability to adapt to network changes efficiently.
  • Accuracy: Provides a complete and up-to-date view of the network, leading to more accurate routing decisions.

Disadvantages of Link State Routing:

  • High Overhead: The transmission of LSAs can lead to high overhead in large networks, especially when LSAs are frequently exchanged.
  • Complexity: The algorithm is more complex to implement compared to other algorithms like Distance Vector Routing.
17. Define Email. Explain the components of Email.

Email (Electronic Mail) is a method of exchanging digital messages over the internet or other computer networks. It allows users to send and receive text, multimedia files, documents, and links quickly and efficiently.

Components of Email:

  1. User Interface:

    • The interface used to compose, send, and read emails.

    • Examples: Email applications (e.g., Outlook, Gmail) or webmail interfaces.

  2. Message Header:

  • Contains metadata about the email, including:
    • From: Sender’s email address.
    • To: Recipient’s email address.
    • CC/BCC: Carbon Copy (CC) and Blind Carbon Copy (BCC) recipients.
    • Subject: A brief description of the email content.
    • Date: Timestamp of when the email was sent.
  • Message Body:

    • The main content of the email, which can include:

      • Text (plain or formatted).

      • Embedded images, links, or attachments.

  2. Attachments:

    • Files or documents included with the email, such as PDFs, images, or spreadsheets.

  3. Mail Servers:

  • Email systems use servers to send, store, and retrieve emails.
    • SMTP (Simple Mail Transfer Protocol): Used for sending emails.
    • IMAP (Internet Message Access Protocol): Used for accessing and managing emails on a remote server.
    • POP3 (Post Office Protocol): Used for downloading emails to a local device.

  1. Email Address:

    • A unique identifier for the sender and recipient.

    • Format: username@oci.com (e.g., ourcreativeinfo@gmail.com).

Advantages of Email:

  • Quick and cost-effective communication.

  • Supports multimedia and file sharing.

  • Accessible from any device connected to the internet.

Disadvantages of Email:

  • Vulnerable to spam and phishing.
  • Requires an internet connection.

III. Answer any TWO of the following (2*10=20)

18. Define switching. Explain Message switching technique in detail.

Switching:

Switching is the process of directing data or messages between devices in a network to ensure they reach their intended destination efficiently. It is essential in network communication to manage how data is transmitted across interconnected devices.

Message Switching:

Message switching is a technique where the entire message is transmitted from the sender to the receiver in a “store-and-forward” manner. In this method, the message is first stored at intermediate nodes and then forwarded to the next node until it reaches its destination.

Key Features of Message Switching:

  1. Store-and-Forward:

    • Each intermediate node stores the entire message before forwarding it.

  2. No Direct Path Required:

    • A direct connection between the sender and receiver is not necessary. Messages are sent through available routes.

  3. Variable Message Size:

    • Messages can vary in size and may take longer if large.

  4. No Real-Time Communication:

    • As messages are stored at intermediate nodes, delays may occur, making it unsuitable for real-time applications.

Working of Message Switching:

  1. Message Generation:

    • The sender creates a complete message and adds destination details.

  2. Storage at Intermediate Nodes:

    • The message is sent to the first node, which stores it until the next node in the path is ready to receive it.

  3. Forwarding:

    • The message is forwarded from node to node until it reaches its final destination.

  4. Delivery to Receiver:

    • At the destination node, the message is delivered to the recipient.

Advantages of Message Switching:

  1. Efficient utilization of network resources, as no dedicated path is required.

  2. Messages are guaranteed to reach the destination, as they are stored at intermediate nodes.

  3. Suitable for sending large amounts of data.

Disadvantages of Message Switching:

  1. High delay due to the store-and-forward mechanism.

  2. Requires significant storage at intermediate nodes.

  3. Inefficient for real-time communication, such as voice or video calls.

19. a & b
a) Explain any three types of network topologies.

  1. Star Topology:

    • Define: All nodes are individually connected to a central hub or switch.
    • Advantages: Easy troubleshooting and management; adding/removing devices is simple.
    • Disadvantages: Single point of failure at the hub; higher costs due to more cabling.

  2. Bus Topology:

    • Define: All devices share a single central cable (the bus) for communication.
    • Advantages: Simple setup and cost-effective for small networks.
    • Disadvantages: Limited cable length; performance can degrade with more devices; hard to troubleshoot.

  3. Ring Topology:

    • Define: Each device is connected to two others, forming a circular path for data transmission.
    • Advantages: Reduced data collisions and predictable performance.
    • Disadvantages: Single point of failure; difficult troubleshooting; adding/removing devices can disrupt the network.
b) Explain token bucket algorithm.
20. a & b

The Token Bucket Algorithm is a traffic shaping and rate-limiting mechanism used in computer networks to control data transmission rates.

How It Works:

  1. A “bucket” holds tokens, where each token represents the right to send a fixed amount of data (e.g., one byte or one packet).
  2. Tokens are added to the bucket at a constant rate, up to the bucket’s capacity.
  3. To send data, tokens are removed from the bucket. If there are insufficient tokens, the data must wait until tokens are available.
  4. Unused tokens can accumulate up to the bucket’s capacity, allowing bursts of traffic.

Key Features:

  • Allows for controlled bursts of traffic while maintaining an average rate.
  • Ensures smoother traffic flow compared to fixed-rate algorithms.

Advantages:

  • Supports both constant and bursty traffic patterns.
  • Simple to implement and effective for rate control.

Disadvantage:

  • May delay packets if tokens are not available.
a) Explain features of TCP.
b) Explain TCP header format.

  • Connection-Oriented:

    • TCP establishes a reliable connection between the sender and receiver before data transfer begins, ensuring both parties are ready to communicate.

  • Reliable Data Transfer:

    • It ensures data is delivered accurately and in order, using error-checking mechanisms, acknowledgments (ACKs), and retransmissions if necessary.

  • Data Segmentation and Reassembly:

    • Large data blocks are divided into smaller segments for transmission, which are reassembled at the receiver’s end in the correct order.

  • Flow Control:

    • TCP uses mechanisms like Sliding Window Protocol to prevent the sender from overwhelming the receiver by adjusting the data transmission rate.

  • Error Detection and Recovery:

    • TCP detects corrupted or lost packets and retransmits them to ensure complete and correct delivery.

  • Full Duplex Communication:

    • TCP allows simultaneous data transfer in both directions, enabling efficient communication.

  • Congestion Control:

    • TCP monitors network congestion and adjusts the data transmission rate to avoid overloading the network.

  • Stream-Oriented Protocol:

    • Data is sent as a continuous stream of bytes rather than individual packets, ensuring smooth and sequential delivery.

  • Port Numbers:

    • TCP uses port numbers to identify specific applications or services on a device, allowing multiple applications to communicate simultaneously.

  • End-to-End Communication:

    • TCP ensures data is transmitted directly between the sender and receiver without interference, maintaining data integrity.

The TCP (Transmission Control Protocol) header is crucial for managing data transmission over networks. It consists of various fields that provide essential information for the reliable delivery of segments. Here’s a short overview of the TCP header format:

TCP Header Format:

    1. Source Port (16 bits): The port number of the sending application.
    2. Destination Port (16 bits): The port number of the receiving application.
    3. Sequence Number (32 bits): Indicates the sequence number of the first byte in this segment, used for ordering.
    4. Acknowledgment Number (32 bits): Indicates the next byte the sender expects to receive, confirming receipt of data.
    5. Data Offset (4 bits): Specifies the length of the TCP header in 32-bit words, indicating where the data begins.
    6. Reserved (6 bits): Reserved for future use, typically set to zero.
    7. Flags (6 bits): Control flags (URG, ACK, PSH, RST, SYN, FIN) used for managing the connection.
    8. Window Size (16 bits): The size of the sender’s receive window for flow control.
    9. Checksum (16 bits): A checksum for error-checking the header and data.
    10. Urgent Pointer (16 bits): If the URG flag is set, this points to urgent data in the segment.
    11. Options (Variable): Can include various TCP options, such as maximum segment size (MSS).
    12. Data (Variable): The actual data being transmitted.

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