MODULE III COMMUNICATION AND NETWORKING NOVEMBER 2023

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2920/301 DATA COMMUNICATION AND NETWORKING
November 2023
Time: 3 Hours

THE KENYA NATIONAL EXAMINATIONS COUNCIL
DIPLOMA IN INFORMATION COMMUNICATION TECHNOLOGY
MODULE III
DATA COMMUNICATION AND NETWORKING

INSTRUCTIONS TO CANDIDATES:
This paper consists of EIGHT questions in FOUR printed pages.
Answer any FIVE of the questions.
Candidates should answer the questions in English.

1.
(a) State two advantages of multiplexing in data communication systems.

Efficient utilization of bandwidth.
Reduction in the number of physical connections.

(b) Distinguish between Frequency Division Multiplexing (FDM) and Time Division Multiplexing (TDM).

FDM: Different channels transmit signals simultaneously on different frequencies.
TDM: Multiple signals are combined into one channel, with each signal assigned a different time slot.

To prevent data overflow by controlling the amount of data sent before receiving acknowledgment.

(d) Mary designed a network for her company by connecting the existing Local Area Network to the Internet. Explain the reason for using the following hardware devices:
(i) Bridge

To connect and filter traffic between two network segments. (ii) Router
To route data between different networks, typically between a local network and the Internet. (iii) NIC
To provide the physical connection between the computer and the network. (iv) Hub
To connect multiple Ethernet devices, making them act as a single network segment.

2.
(a) Halls Company Ltd. is considering replacing their network cables with fibre optic cables. Outline four advantages that fibre optic cable has over twisted pair cables.

Higher bandwidth.
Longer transmission distances.
Immunity to electromagnetic interference.
Better security due to difficulty in tapping.

(b) Describe each of the following terms as used in Broadband Access Control techniques:
(i) Stop and wait

A protocol where the sender stops and waits for an acknowledgment after transmitting a data frame before sending the next one. (ii) Sliding window
A method where multiple frames can be sent before receiving an acknowledgment, with the sender keeping track of unacknowledged frames within a “window.” (iii) Polling
A process where a central controller or server invites each client or device in turn to send data. (iv) Handshaking
The exchange of control signals between devices to establish a communication link.

Flexibility and ease of installation.
Mobility and support for portable devices.
Lower costs compared to wired networks.
Scalability for network expansion.

(d) Figure 1 shows documents that would necessitate the implementation of encryption of network communications. List four documents.

Financial records
Legal contracts
Personal identification information
Trade secrets or proprietary information

3.
(a) Distinguish between synchronous and asynchronous transmission as used in Data Transmission Engineering.

Synchronous Transmission: Data is sent at regular intervals synchronized by a clock signal.
Asynchronous Transmission: Data is sent in an irregular stream with start and stop bits to signify the beginning and end of a byte.

(b) Explain each of the following error detection methods:
(i) Parity check

A method where an extra bit is added to data to ensure that the total number of 1-bits is even (even parity) or odd (odd parity). (ii) Cyclic Redundancy Check (CRC)
A method that applies a polynomial division to data, where the remainder (CRC value) is sent along with the data for error detection.

(c) An organization has installed an ADSL system having data rates designed under Annex L of the ITU-T Standard. Explain three characteristics of Annex L.

Support for long reach ADSL.
Improved performance in rural areas.
Increased data rate over long distances using lower frequencies.

(d) Explain the circumstances that would necessitate the use of Bluetooth in a network.

When connecting devices over short distances, such as within a room.
In scenarios where low power consumption is needed.
For establishing ad-hoc connections between devices.

4.
(a) List four examples of Network Operating Systems.

Windows Server
Linux
UNIX
Novell NetWare

(b) Terna is concerned that users tend to use corporate network for Muhoanga Technical Institute, a basic password will suffice. Outline three considerations to make in the selection of a network operating system.

Compatibility with existing hardware and software.
Security features offered by the OS.
Scalability to handle future network growth.

(c) Using the aid of a diagram, distinguish the most appropriate symmetric key cryptography method from the asymmetric method.

Symmetric Key Cryptography: The same key is used for both encryption and decryption.
Asymmetric Key Cryptography: Uses a pair of keys, one for encryption (public key) and one for decryption (private key).
(Diagram not included)

(d) Outline three advantages of the above technique.

Faster encryption and decryption for symmetric key.
Stronger security for asymmetric key, as private keys are never shared.
Flexibility in key distribution for asymmetric key.

(e) Differentiate between a setup disk and a boot disk as used in the Internet.

Setup Disk: Used to install software or an operating system.
Boot Disk: Used to start up a computer system and load the operating system.

(f) Allan bought a communication software and a DVD video which he intends to use in his new system. Explain two considerations he made for the successful installation of the software.

Compatibility with the operating system.
Sufficient hardware resources (CPU, RAM, disk space).

5.
(a) List four advantages of Network Operating Systems.

Centralized user management.
Enhanced security features.
Easier file and resource sharing.
Improved network monitoring and maintenance.

(b) Indicate one technique of installing the software on the company using DSL Communications.

Remote installation over the network.

Windows-based GUI
Web-based GUI

(d) Differentiate between a baseband and broadband network.

Baseband: Transmits a single signal at a time over the medium.
Broadband: Transmits multiple signals simultaneously over the same medium.

(e) With the aid of an Ethernet system diagram, determine the transmitted data rate for a system with the following components:

Diagram not included.
Data rate is determined by the slowest component in the network.

(f) Outline three techniques that could be applied in this system.

Use of switches instead of hubs.
Implementing Quality of Service (QoS).
Increasing bandwidth by adding more links or upgrading to faster technology.

6.
(a) List two error correction techniques that could be applied in this system.

Forward Error Correction (FEC)
Automatic Repeat Request (ARQ)

(b) List four types of OSI/ISO protocol routers.

Interior Gateway Routing Protocol (IGRP)
Open Shortest Path First (OSPF)
Border Gateway Protocol (BGP)
Routing Information Protocol (RIP)

Simple Mail Transfer Protocol is used for sending and receiving email. (ii) FTP
File Transfer Protocol is used for transferring files between a client and server on a network.

7.
(a) Figure 3 shows a frame format of IEEE 802.3. Use it to answer the question that follows:
(Diagram not included)

(b) Describe the parts labeled (i), (ii), and (iii).
(i) Start of Frame

Indicates the beginning of the data frame.
(ii) Source Address
The MAC address of the device sending the data.
(iii) Data Payload
The actual data being transmitted.

Network Address
Subnet Mask
Gateway Address
Broadcast Address

8.
(a) Figure 2 shows the structure of a structured cable system. Use it to answer the question that follows:
(Diagram not included)

(b) Identify the parts labeled (i), (ii), (iii), and (iv).

(i) Patch Panel
(ii) Cable Tray
(iii) Conduit
(iv) Wall Jack

Physical

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