KNEC November 2021 DICT module 3 Data communication and networking past paper

Data communication and networking questions and answers

1 a) Differentiate between analog and digital signals as used in data communication (4 Marks)

  1. Analog Signals: Analog signals are continuous and can take on any value within a range. They are represented by waves that vary in amplitude and frequency. Examples of analog signals include sound waves and radio waves.
  2. Digital Signals: Digital signals are discrete and can only take on specific values. They are represented by sequences of 0s and 1s (binary digits). Examples of digital signals include computer data and digital audio.

b)Explain 3 functions of physical layer in OSI model (6 Marks)

  1. Encoding and Decoding of Signals: The Physical Layer is responsible for encoding the data to be transmitted into a physical signal that can be transmitted over a physical medium, such as a copper wire, fiber optic cable, or radio wave. The encoding and decoding process involves converting digital data into analog signals and vice versa. The physical layer also handles signal modulation and demodulation to ensure the signal can be transmitted accurately over the communication channel.
  2. Transmission of Data: The Physical Layer is responsible for transmitting the encoded data over the physical medium. This involves managing the physical characteristics of the transmission medium, such as voltage levels, signal strength, and frequency. The physical layer also ensures that the transmitted signal conforms to the communication protocol and standards for the specific medium, such as Ethernet or Wi-Fi.
  3. Signal Reception and Demodulation: The Physical Layer is responsible for receiving the transmitted signal from the communication medium and converting it back into digital data. This involves signal demodulation and decoding to extract the original digital data from the physical signal. The physical layer also handles error detection and correction mechanisms to ensure that the data received is accurate and free from errors caused by noise or interference.

c)User datagram protocol header is made up of several fields. Explain three fields that could be found in the header (6 Marks)

  1. Source and Destination Port Numbers: The UDP header contains two 16-bit fields for the source and destination port numbers. These fields specify the application or process on the source and destination devices that are responsible for handling the data in the datagram. By using port numbers, multiple applications or processes can use UDP to send and receive data over the same network connection.
  2. Length Field: The length field in the UDP header is a 16-bit field that specifies the total length of the UDP datagram, including the header and data fields. This field allows the receiving device to determine the length of the datagram and ensure that it has received the entire packet correctly. If the length of the datagram is too long to fit into a single packet, the data will be fragmented and sent in multiple packets.
  3. Checksum Field: The UDP header also contains a 16-bit checksum field, which is used to verify the integrity of the data in the datagram. The checksum is calculated over the entire datagram, including the header and data fields, using a mathematical algorithm. The receiving device can then calculate its own checksum over the datagram it received and compare it to the checksum in the header. If the checksums match, the datagram is considered to be error-free. If they do not match, the datagram is considered to be corrupt and is discarded.

d)Mary intends to use command line network operating system for her computer network. Outline four advantages of the operating system that could have influenced her choice (4 Marks)

  1. Flexibility: Command line NOS provide a high degree of flexibility and control over the network. Unlike graphical user interfaces, which may have limited options and settings, command line NOS can be configured and customized to suit the needs of the user. This makes it easier to manage complex network configurations and perform advanced tasks such as scripting and automation.
  2. Efficiency: Command line NOS can be more efficient than graphical user interfaces, particularly when managing large networks. This is because command line NOS require less system resources and can be faster to navigate and execute commands. Additionally, experienced users can often perform tasks more quickly using command line NOS than through a graphical user interface.
  3. Security: Command line NOS can be more secure than graphical user interfaces, as they are less vulnerable to attacks from malware and viruses. This is because command line NOS are typically designed to be used by trained professionals who have a good understanding of network security best practices. Additionally, command line NOS can be configured to limit access to certain commands or functions, reducing the risk of accidental or malicious misuse.
  4. Cost: Command line NOS can be more cost-effective than graphical user interfaces, as they typically require less hardware and software resources. Additionally, many command line NOS are open source, which means that they are free to use and can be customized to meet the needs of the user. This can be particularly beneficial for small businesses or organizations with limited IT budgets.

2. a) Outline four types of communication software that could be found in a computer(4 Marks)

  1. Email software: Email software allows users to send, receive, and manage electronic messages over the Internet or a computer network. Examples of email software include Microsoft Outlook, Gmail, Yahoo! Mail, and Apple Mail.
  2. Instant messaging software: Instant messaging (IM) software enables users to send and receive real-time text messages over the Internet or a local network. Examples of IM software include WhatsApp, Facebook Messenger, Slack, Skype, and iMessage.
  3. Video conferencing software: Video conferencing software allows users to hold virtual meetings and communicate with others in real-time via video and audio. Examples of video conferencing software include Zoom, Microsoft Teams, Google Meet, and Cisco Webex.
  4. VoIP software: Voice over Internet Protocol (VoIP) software enables users to make phone calls over the Internet rather than using traditional telephone lines. Examples of VoIP software include Skype, WhatsApp, Viber, and Google Voice.

b)For each of the following scenarios, suggest the most appropriate internet connection justifying your answer;

  1. A host server that is accessed by millions of users:(1 Mark)

For a host server that is accessed by millions of users, a dedicated leased line would be the most appropriate internet connection. This type of connection provides a direct, uncontended connection between the server and the internet, ensuring that users can access the server quickly and reliably at all times.

  1. A home office that uses existing telephone lines:(1 Marks)

For a home office that uses existing telephone lines, a Digital Subscriber Line (DSL) or cable internet connection would be the most appropriate. DSL uses existing phone lines to provide high-speed internet access, while cable internet uses existing cable TV lines. Both of these connections provide reliable and fast internet access suitable for a home office.

  1. A video chat on a mobile phone:(1 Marks)

For a video chat on a mobile phone, a 4G or 5G mobile data connection would be the most appropriate internet connection. These mobile data connections provide high-speed internet access on the go, allowing for reliable video chats without the need for a fixed internet connection.

  1. Connecting several branches of a company located in various towns:(1 Marks)

For connecting several branches of a company located in various towns, a Virtual Private Network (VPN) would be the most appropriate internet connection. This type of connection creates a secure and private network connection over the internet, allowing users to access resources and communicate with each other as if they were on the same local network. This connection can be achieved using any type of internet connection, including DSL, cable, fiber optic, or leased lines.

ci) Outline 2 uses of a network baseline during network troubleshooting(2 Marks)

  1. Identifying deviations from normal network behavior: By establishing a baseline of network performance, administrators can monitor network traffic and behavior over time to identify any deviations from the normal baseline. For example, if network traffic suddenly spikes or a particular device starts generating unusually high levels of traffic, this can be an indicator of a potential issue. By using the baseline as a reference, administrators can quickly identify the source of the issue and take steps to resolve it.
  2. Analyzing network performance over time: By collecting and analyzing network performance data over time, administrators can identify trends and patterns in network behavior that may indicate potential issues. For example, if a particular application is experiencing slow response times or frequent outages, administrators can use the network baseline to identify whether the issue is related to the application itself or to the network infrastructure supporting it. By comparing current performance data to the baseline, administrators can quickly identify any performance issues and take appropriate action to resolve them.

ii)Unipolar encoding scheme has several problems that makes it unpopular in modern digital transmission schemes. Explain two such problems(4 Marks)

  1. No signal transitions: One major issue with unipolar encoding is that it does not provide any signal transitions, which can make it difficult to synchronize the receiver clock with the transmitted data. Since the signal is always either high or low, it is difficult for the receiver to determine where one bit ends and the next one begins. This can lead to clock synchronization errors and data loss.
  2. Inability to carry DC components: Another issue with unipolar encoding is that it cannot carry DC components. Since the signal is always above or below the reference voltage level, it cannot carry any DC components, which are required for some applications such as audio and video transmission. This can result in signal distortion and loss of data, making unipolar encoding unsuitable for applications that require the transmission of DC components.

di) Outline two roles of simple mail transfer protocol(2 Marks)

  1. Email Transmission: The primary role of SMTP is to transmit email messages between email clients and email servers. SMTP is responsible for delivering messages from the sender’s email client to the recipient’s email server, using a series of handshaking commands to establish a reliable connection between the two. Once the connection is established, SMTP sends the message data in a structured format, including the sender and recipient email addresses, subject, body, and any attachments.
  2. Email Routing: Another important role of SMTP is email routing. SMTP servers communicate with each other using a set of rules to determine the most efficient path for delivering messages to their final destination. When a message is sent from one email server to another, the receiving server uses DNS (Domain Name System) to look up the recipient’s domain name and find the correct mail server to receive the message. This process is known as email routing, and it is a critical part of the SMTP protocol as it ensures that messages are delivered to the correct destination in a timely and efficient manner.

ii)The figure below shows a twisted pair cable STP name parts and state their functions(4 Marks)

twisted pair cable is a type of copper cable commonly used for telecommunications and networking applications. Here are the different parts of twisted pair cable and their functions:

  1. Conductors: Twisted pair cables have two conductors, typically made of copper. These conductors carry the electrical signal between devices connected by the cable.
  2. Insulation: The conductors are coated with a layer of insulation, usually made of plastic. The insulation helps to prevent interference and crosstalk between the two conductors.
  3. Twisted Pairs: The two conductors are twisted together in a specific pattern, which helps to reduce electromagnetic interference (EMI) and crosstalk between wires. The twisting of the wires creates a balanced transmission line, which helps to minimize noise and distortion.
  4. Jacket: The twisted pair cable is covered with a protective outer layer called a jacket. The jacket protects the cable from physical damage and environmental factors such as moisture, temperature, and UV radiation.
  5. Shielding: Some twisted pair cables have an additional shielding layer, usually made of metal. This shielding layer helps to reduce interference from external sources, such as electromagnetic radiation from other devices.
  6. Connector: At each end of the cable, there is a connector that attaches the cable to a device, such as a computer or a router. The connector is usually made of metal and has contacts that connect to the conductors in the cable, allowing for the transfer of data.

3a) Describe three organizations that regulates WLAN (6 Marks)

  1. Institute of Electrical and Electronics Engineers (IEEE): The IEEE is a professional organization that creates and maintains standards for the telecommunications and computer networking industry, including wireless LANs. The IEEE 802.11 standards specify the protocols for wireless local area networks (WLANs).
  2. Wi-Fi Alliance: The Wi-Fi Alliance is a nonprofit organization that promotes the adoption and interoperability of wireless networking technologies based on the IEEE 802.11 standards. The alliance certifies products that meet their standards and helps ensure the compatibility of different products from various manufacturers.
  3. Federal Communications Commission (FCC): The FCC is a government agency in the United States that regulates the use of wireless communication devices and technologies. The FCC sets limits on the amount of power that can be used by wireless devices and also regulates the frequencies and channels that can be used for wireless communication. The FCC also establishes guidelines for the testing and certification of wireless devices to ensure their compliance with federal regulations.

b)Kate designed a computer network that used hybrid topology. Outline four factors that could have influenced her design(4 Marks)

  1. Scalability: Kate may have considered the scalability of the network when designing it. A hybrid topology can be a good choice for a network that needs to accommodate future growth, as it allows for flexibility in adding or removing devices as needed.
  2. Cost: The cost of the network infrastructure may have been a factor in Kate’s design decisions. A hybrid topology can be more expensive to implement than a simpler topology, such as a star topology, because it requires additional equipment like bridges, routers, or switches to connect the different topologies.
  3. Redundancy: Kate may have considered redundancy in her network design. A hybrid topology can provide redundancy by allowing for multiple paths between devices, which can help ensure that the network remains functional even if one or more components fail.
  4. Performance: The performance requirements of the network may have influenced Kate’s design choices. A hybrid topology can offer better performance than a single topology by combining the strengths of different topologies. For example, a hybrid topology that combines a bus topology with a ring topology can offer both scalability and fault tolerance. Kate may have chosen to incorporate different topologies based on their individual strengths to meet the specific performance requirements of her network.

c)Differentiate between next-generation firewall and cloud firewall(4 Marks)

Next-generation firewalls (NGFWs) and cloud firewalls are two types of firewalls that can provide different types of network security. Here are the key differences between these two firewall technologies:

  1. Deployment: NGFWs are typically deployed on-premises, while cloud firewalls are deployed in the cloud. NGFWs are installed on a company’s network devices, such as routers or switches, and provide security for traffic that passes through those devices. Cloud firewalls, on the other hand, are provided as a service by cloud service providers and are deployed in the cloud to protect cloud-based applications and services.
  2. Scalability: Cloud firewalls are designed to be highly scalable to accommodate the dynamic nature of cloud environments. As cloud resources are added or removed, cloud firewalls can adjust their configurations to protect those resources. NGFWs are typically less scalable and may require additional hardware to accommodate changes in network traffic.

d)Dynamic host configuration protocol (DHCP) is used to automate IP addressing in a network. explain three components of this protocol(6 Marks)

  1. DHCP server: The DHCP server is a device or software that assigns IP addresses to devices on the network. The DHCP server receives a request from a client device for an IP address and responds by providing the client with an available IP address from a pool of addresses configured on the server. The server also provides other configuration parameters, such as subnet mask and default gateway.
  2. DHCP client: The DHCP client is a device that requests an IP address from the DHCP server. When a client device connects to the network, it sends a DHCP discover message to locate an available DHCP server. Once the client receives a response from a DHCP server, it accepts the IP address and other network configuration parameters provided by the server.
  3. DHCP relay agent: A DHCP relay agent is a device that helps forward DHCP messages between clients and DHCP servers on different subnets. If a client device is located on a different subnet than the DHCP server, the DHCP relay agent can forward the DHCP discover message to the DHCP server on behalf of the client. The DHCP relay agent can also forward the DHCP server’s response back to the client on the appropriate subnet.

4a)Explain each of the following terms as used in the internet; attachment; Favourite(4 Marks)


An attachment refers to a file that is added to an email, message or post to be sent over the internet. An attachment can be any kind of digital file, including documents, images, audio, and video files. When sending an attachment, it is uploaded to a server and then downloaded by the recipient. Attachments are commonly used to share files between individuals, businesses or organizations, and are an important way to send and receive information online.


A favorite, also known as a bookmark or a “like,” is a feature on many internet platforms that allows users to mark or save content they find interesting or want to revisit later. When a user “favorites” a piece of content, it is typically stored in a designated area of the website or app for easy access. For example, on social media platforms like Twitter and Instagram, users can “like” or “favorite” a post by clicking a heart icon, which adds the post to a list of their favorite posts. On web browsers, users can bookmark a webpage they want to revisit later by clicking on a star icon, which saves the webpage to their list of bookmarks. Favorite features help users organize their online experience and easily access content they enjoy or find useful.

b) Peter was advised by his friend to use unattended installation for a network software. Outline four advantages of using this installation method (4 Marks)

  1. Time-saving: With unattended installation, the software can be installed on multiple computers simultaneously without any user interaction, which can save a lot of time and effort compared to manually installing software on each individual computer.
  2. Consistency: Unattended installation ensures that the software is installed with the same configuration and settings on each computer, ensuring consistency across the network. This can be important for organizations that require standardization and consistency in their IT infrastructure.
  3. Reduced Errors: With no need for user interaction, there is less chance of human error during installation, which can reduce the risk of mistakes and issues that may arise when software is installed manually.
  4. Enhanced Security: Unattended installation can be configured to include security measures such as passwords or firewalls, making it easier to ensure that security protocols are consistently applied across the network. This can help organizations maintain a secure and stable IT environment.

c)Judy discovered several network vulnerabilities in her company’s network. Outline four examples of these vulnerabilities she could have noted.(4 Marks)

  1. Weak Passwords: Weak passwords can make it easy for hackers to gain access to a network. Judy may have discovered that many employees were using weak passwords, such as “password” or “123456,” which can be easily guessed or cracked.
  2. Outdated Software: Outdated software can have security vulnerabilities that hackers can exploit to gain access to a network. Judy may have found that some software or operating systems on the company’s network were not up-to-date, leaving the network vulnerable to attacks.
  3. Unsecured Wireless Networks: An unsecured wireless network can be easily accessed by anyone within range, potentially allowing hackers to gain access to a network. Judy may have discovered that the company’s wireless network was not secured with encryption or password protection, leaving the network vulnerable to attacks.
  4. Phishing Attacks: Phishing attacks involve tricking employees into divulging sensitive information, such as login credentials or personal information. Judy may have discovered that some employees had fallen victim to phishing attacks, potentially giving hackers access to the company’s network.

di) Alice intends to use WIMAX (worldwide interoperability for microwave access) to interconnect the two network branches located in a town. Explain two features of this transmission media that could have influenced her decision.(4 Marks)

  1. High Bandwidth: WIMAX has a high bandwidth, which means it can support high data rates over long distances. This makes it a good choice for interconnecting two network branches that are separated by a significant distance, as it can provide fast and reliable data transmission between the two locations.
  2. Line-of-Sight Not Required: WIMAX does not require a direct line-of-sight between the transmitter and receiver, which makes it easier to install and use in urban areas where buildings or other obstacles may block the signal. This feature makes WIMAX a good choice for interconnecting two network branches located in a town, as it can provide reliable transmission even if there are buildings or other obstacles between the two locations.

ii)Explain two challenges of a bus network topology(4 Marks)

  1. Limited Scalability: Bus networks can be challenging to scale up as the number of devices on the network grows. This is because adding more devices can increase network traffic and cause collisions, which can slow down data transmission and reduce network performance. To address this issue, additional network segments and repeaters may be needed, which can add complexity and cost to the network.
  2. Single Point of Failure: In a bus network, if the main communication line (the bus) fails, the entire network can be affected. This can result in network downtime, loss of data, and disruption to business operations. To mitigate this risk, redundant or backup communication lines may be needed, which can add complexity and cost to the network
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