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COSC 361: COMPUTER NETWORKS 1 PROTOCTORED EXAMCOMPUTER SCIENCE
PAPER 1
Question ONE (30 marks)
a) Differentiate between host-based firewalls and network-based firewalls (4 marks)
Host-based firewalls and network-based firewalls are two different approaches to network
security:
Host-based firewalls: These are installed on individual devices, such as computers or
servers. They provide protection at the host level, monitoring and controlling
network traffic to and from that specific device. Host-based firewalls are often
tailored to the specific needs of the host system and are typically more customizable
in terms of rules and policies.
Network-based firewalls: Network-based firewalls are typically deployed at the
perimeter of a network, like a router or a dedicated firewall appliance. They filter
and control traffic entering or exiting the entire network. Network-based firewalls
are designed to protect multiple devices within a network and are often used for
overall network security.
b) State Two factors to consider during network design (2 marks)
Two factors to consider during network design are:
Scalability: When designing a network, it's essential to consider how it can grow and
adapt to changing requirements. Scalability ensures that the network can
accommodate additional users, devices, and services without major architectural
changes.
Redundancy: Network design should incorporate redundancy to ensure high
availability. Redundant components, such as backup servers, power supplies, or
internet connections, help minimize downtime in case of failures.
c) Explain three objectives of network security (6 marks)
Three objectives of network security are:
Confidentiality: Protecting sensitive information from unauthorized access. This
involves encryption, access controls, and data classification.
Integrity: Ensuring that data remains unaltered and trustworthy during transmission
and storage. This can be achieved through checksums, digital signatures, and access
controls.
Availability: Ensuring that network resources and services are accessible when
needed and free from disruptions caused by outages, attacks, or other incidents.
This involves redundancy and fault tolerance mechanisms.
d) Explain attacks that target computer networks and how they can be protected (6Marks)
Attacks that target computer networks include:
DDoS (Distributed Denial of Service) attacks: Attackers overwhelm a network with
traffic, making it unavailable to users. Protection involves traffic filtering and
redundancy.
Malware: Malicious software like viruses, worms, and ransomware can infect
networked devices. Protection involves antivirus software, user education, and
network segmentation.
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, Phishing: Attackers use deceptive emails or websites to trick users into revealing
sensitive information. Protection involves user awareness and email filtering
e) Differentiate between
i. Server-based architecture and peer-based architecture
Server-based architecture: In this architecture, a central server controls and
manages resources and services. Clients (end-user devices) request services
from the server. It's a more centralized approach.
Peer-based architecture: In this architecture, there is no central server.
Instead, all devices (peers) have equal status and can communicate directly
with each other. It's a more decentralized approach, often used in peer-to-
peer (P2P) networks
ii. Ethernet technology and token-passing technology
Ethernet technology: Ethernet is a common LAN (Local Area Network)
technology that uses a shared communication medium. Devices on the
network can transmit data when the communication channel is clear, and
collisions are resolved using protocols like CSMA/CD (Carrier Sense Multiple
Access with Collision Detection).
Token-passing technology: Token-passing networks use a token (a special
data packet) to control access to the communication medium. Only the
device holding the token can transmit data. This technology is often used in
networks like Token Ring, where collisions are avoided, and network access
is more controlled.
Question TWO (20 marks)
a) Differentiate between intranet and extranet
Intranet: An intranet is a private network that is limited to an organization's internal use.
It is used for sharing information, resources, and collaboration within the organization.
Access is usually restricted to employees or authorized personnel. It is not accessible to
the public or external entities.
Extranet: An extranet is an extension of an intranet that allows authorized external
parties, such as partners, suppliers, or customers, to access specific resources or
information. It provides a controlled and secure environment for collaboration beyond
the organization's boundaries. Access is still restricted, but it includes external entities.
b) Describe the impact of the Internet on businesses.
The Internet has had a profound impact on businesses in several ways:
Global reach: The Internet enables businesses to reach a global audience, expanding
their customer base and market reach.
E-commerce: Online stores and digital marketplaces have transformed the way
businesses sell products and services. E-commerce has become a significant revenue
source for many companies.
Marketing and advertising: Digital marketing and advertising tools allow businesses to
target specific demographics and track the effectiveness of their campaigns more
precisely.
Communication and collaboration: The Internet facilitates efficient communication
within and outside the organization. Tools like email, video conferencing, and project
management software have improved collaboration.
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, Information access: Quick and easy access to information on the Internet helps
businesses stay informed about industry trends, competitors, and customer preferences.
Cost savings: Online tools and cloud services reduce the need for physical infrastructure,
leading to cost savings in data storage, software, and hardware.
Data analytics: Businesses can gather and analyze vast amounts of data from online
sources to make data-driven decisions and improve their operations.
Security challenges: The Internet has also brought security concerns, such as data
breaches and cyberattacks, which businesses must address to protect sensitive
information.
c) Explain the various protocols found in the application layer of the OSI model. (8 Marks)
The application layer of the OSI model deals with end-user applications and services. Several
protocols operate at this layer, including:
HTTP (Hypertext Transfer Protocol): Used for web browsing and transferring web pages,
it enables communication between web browsers and web servers.
SMTP (Simple Mail Transfer Protocol): Used for sending email messages, SMTP handles
the transmission of emails between clients and email servers.
FTP (File Transfer Protocol): FTP is used for transferring files over a network. It allows
users to upload and download files to and from remote servers.
POP3 (Post Office Protocol version 3) and IMAP (Internet Message Access Protocol):
These protocols are used for retrieving email messages from mail servers to email
clients.
SNMP (Simple Network Management Protocol): SNMP is used for managing and
monitoring network devices, such as routers, switches, and servers.
DNS (Domain Name System): DNS resolves human-readable domain names to IP
addresses, making it possible to locate resources on the Internet.
HTTPS (Hypertext Transfer Protocol Secure): An extension of HTTP, HTTPS encrypts data
exchanged between web clients and servers, ensuring secure communication.
Telnet: Telnet provides remote access to devices over a network, allowing a user to
control or manage remote systems.
These protocols facilitate a wide range of applications and services at the application layer of the
OSI model.
Question THREE (20 marks)
a) Explain the two categories of Communication Software. (4 Marks)
Real-Time Communication Software: This category of communication software is
designed for immediate, synchronous communication. It includes applications like
instant messaging, video conferencing, and Voice over IP (VoIP) software. Real-time
communication software enables users to interact and exchange information in real-
time, making it suitable for conversations and collaborations that require instant
responses.
Store-and-Forward Communication Software: Store-and-forward communication
software is used for asynchronous communication. It involves sending messages or
data that are stored temporarily at intermediary points (e.g., email servers) and
forwarded when the recipient is available. Email is a common example of store-and-
forward communication software. It allows users to send messages that can be
retrieved by the recipient at their convenience.
b) State three general functions of communication software (4 Marks)
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, Message Creation and Composition: Communication software allows users to create
and compose messages, whether they are text-based (e.g., emails), multimedia
messages (e.g., photos or videos), or voice messages. Users can format, edit, and
customize their messages before sending them.
Message Transmission and Delivery: Communication software is responsible for
transmitting messages from the sender to the recipient. It manages the process of
sending data over a network, ensuring it reaches the intended destination reliably
and efficiently.
Message Reception and Access: Communication software provides mechanisms for
users to receive and access incoming messages. This includes notification of new
messages, message storage, and user interfaces for reading, listening to, or viewing
messages.
c) Explain the factors that determine the maximum length of any transmission media. (4
Marks)
Propagation Delay: Propagation delay is the time it takes for a signal to travel from
the sender to the receiver. The longer the transmission medium, the greater the
propagation delay. High propagation delay can limit the maximum length of the
medium, especially in real-time applications.
Signal Attenuation: Signal attenuation refers to the weakening of a signal as it travels
over a medium. Over longer distances, signals can weaken to the point where they
are no longer distinguishable from noise, limiting the maximum length of the
transmission medium.
Interference and Noise: External interference and noise from other devices or
electromagnetic sources can corrupt signals during transmission. Longer
transmission media are more susceptible to interference and noise, which can
reduce the maximum length.
Transmission Rate (Bandwidth): The higher the data transmission rate (bandwidth),
the more susceptible the signal is to attenuation and distortion over longer
distances. To maintain signal quality, the maximum length may need to be reduced.
d) Explain four factors to consider when choosing a topology. (8 Marks)
Scalability: The ability to expand the network easily to accommodate more devices
or users. Some topologies, like a star topology, are more scalable than others.
Reliability and Redundancy: Consider the network's fault tolerance and redundancy.
Redundant links or devices can help maintain network functionality in case of
failures.
Cost: The cost of implementation, including cabling, hardware, and maintenance, is
a crucial factor. Some topologies may be more cost-effective than others.
Performance and Speed: The topology's impact on data transfer speed and latency is
essential. Some topologies, like a fully connected mesh, provide high-speed
connections but can be costly.
Security: Different topologies have varying levels of inherent security. Consider how
easy it is to secure the network against unauthorized access and data breaches.
Management and Maintenance: The ease of network management and
maintenance is another critical factor. Some topologies are simpler to administer
than others.
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