1.1 User Needs Collections

1.1.1 Introduction to Computer Networking

Computer networking involves connecting multiple computers and devices to share resources and information. It enables communication between users and systems, facilitating tasks such as data sharing, internet access, and application deployment. In Kenya, institutions like county government offices rely heavily on networks to coordinate service delivery and manage data efficiently.

Definition of Computer Networking

Computer networking is the practice of linking computers and other devices to facilitate communication and resource sharing. This connection can be established via wired or wireless technologies, enabling users to send data, access services, and collaborate remotely.

Purpose of Computer Networks

Networks enable resource sharing including printers, files, and internet connectivity, reducing costs and improving productivity. For example, a university's computer lab network allows students to access centralized databases and learning management systems seamlessly.

Benefits of Computer Networks

• Resource Sharing: Networks allow multiple users to share hardware and software resources, reducing redundancy.
• Data Accessibility: Users can access data from any connected device, enhancing collaboration.
• Communication Efficiency: Email and instant messaging systems operate efficiently over networks.
• Centralized Management: Network administrators can manage security policies and updates centrally.
• Scalability: Networks can be expanded to accommodate growing organizational needs without complete redesign.

Challenges in Computer Networking

• Security Risks: Networks are vulnerable to unauthorized access and cyber-attacks.
• Complexity: Designing and maintaining networks requires skilled personnel.
• Cost: Initial setup and equipment can be expensive.
• Compatibility Issues: Different devices and protocols may not interoperate smoothly.
• Reliability: Network failures can disrupt business operations significantly.

Why This Unit Begins With User Needs

A network is built for the people who will use it, not for its own sake. Everything that follows, the type of network, the topology, the components and the cost, is decided by what the users actually need it to do. A technician who starts by choosing equipment is guessing. One who starts by collecting requirements is designing.

1.1.2 Computer Network Types

Understanding the types of computer networks is essential to choosing the right network design for an organization's needs. Kenyan businesses and institutions vary widely in size and scope, necessitating different network configurations.

Local Area Network (LAN)

A LAN connects computers within a limited geographical area such as an office, school, or hospital. It supports high data transfer speeds and is typically owned and managed by the organization. For instance, a SACCO office may use a LAN to connect teller terminals, accounting software, and printers.

Wide Area Network (WAN)

WANs cover large geographical areas, connecting multiple LANs through public or private communication links. The internet is the largest example of a WAN. County governments may use WANs to link various departmental offices across different regions.

Metropolitan Area Network (MAN)

MANs span a city or metropolitan area, larger than LANs but smaller than WANs. They are often used by universities or large corporations to connect multiple campuses. For example, a university with multiple campuses in Nairobi might use a MAN to share resources efficiently.

Personal Area Network (PAN)

PANs are small networks centered around an individual's devices, typically within a few meters. Examples include Bluetooth connections between a smartphone and a laptop. In retail shops, PANs can connect barcode scanners and point-of-sale terminals.

Wireless Networks

Wireless networks use radio waves instead of physical cables. Wi-Fi networks in hotels provide guests with internet connectivity without the need for wired connections, enhancing mobility and convenience.

1.1.3 Network Topologies

Network topology refers to the physical or logical arrangement of devices in a network. It influences performance, fault tolerance, and scalability of the network, making it a critical design consideration for ICT technicians.

Bus Topology

In bus topology, all devices are connected to a single communication line. It is simple and cost-effective but suffers from performance degradation as more devices are added. Small retail outlets may use bus topology for connecting a few computers to a shared printer.

Star Topology

Star topology connects all devices to a central hub or switch. It offers easy management and fault isolation since each device has a dedicated connection. County offices often use star topology to connect workstations to a central server room.

Ring Topology

Devices are connected in a circular fashion, with data passing through each node until it reaches its destination. It provides equal access to all nodes but is vulnerable to a single point of failure unless a dual ring is implemented. Some telecommunications networks in Kenya use ring topology for redundancy.

Mesh Topology

Mesh topology connects each device to multiple others, providing high redundancy and fault tolerance. It is expensive and complex but ideal for critical networks where downtime is unacceptable, such as hospital networks managing patient data.

Hybrid Topology

Hybrid topology combines two or more different topologies to leverage their advantages. Large organizations with diverse departments, such as universities, often use hybrid topologies to accommodate varying network demands.

1.1.4 Components of a Computer Network

A computer network comprises various hardware and software elements working together to facilitate communication and resource sharing. Understanding these components enables ICT technicians to design and troubleshoot networks effectively.

Network Interface Cards (NICs)

NICs provide the physical interface between a computer and the network. They convert data into signals compatible with the network medium, whether wired or wireless.

Switches

Switches connect multiple devices within a LAN, directing data packets efficiently to their destinations. This reduces network traffic and improves performance compared to hubs.

Routers

Routers connect different networks, such as LANs and WANs, directing data packets based on IP addresses. They enable internet access and manage traffic between subnetworks in institutions like hospitals.

Transmission Media

Transmission media carry data signals between devices. Examples include twisted-pair cables, fiber optic cables, and wireless radio waves. Fiber optics are increasingly used by Kenyan ISPs to provide high-speed internet.

Network Operating Systems (NOS)

NOS manage network resources, user permissions, and security protocols. Examples include Windows Server and Linux-based systems that run servers in universities and corporate offices.

1.1.5 Computer Network User Requirements/Needs

Collecting user requirements is the foundation of network design. Understanding what users need ensures the network supports business processes efficiently and securely.

Types of Requirements

• Functional requirements: What the network must do. Users must be able to share a printer, access the internet, reach the accounting server, make voice calls over the network.
• Non-functional requirements: How well it must do it. Speed, uptime, response time, number of simultaneous users, security level.
• Constraints: What limits the design. Budget, the existing building, available power, the skills of the staff who will maintain it, and the time available.

A requirement that cannot be tested is not a requirement. "The network should be fast" cannot be verified. "Transactions must complete within two seconds with 40 users logged in" can.

Steps in Collecting User Requirements

Step 1: Identify the stakeholders

Find out who has an interest in the network before asking anything. They are not all users:

• End users: the staff who will work on it daily.
• Management: who approve the budget and set the business priorities.
• ICT staff: who will run and maintain it.
• External parties: the internet service provider, auditors, and any regulator with requirements of its own.

Missing a stakeholder is the commonest cause of a network that fails on handover. The accounts department that was never consulted turns out to need a dedicated link to the bank.

Step 2: Plan the collection

Decide what information is needed, from whom, by what method, and by when. Prepare the questions in advance. Book appointments rather than interrupting people at work, since a rushed answer is a wrong answer.

Step 3: Collect the requirements

Use more than one method, since each reveals something the others miss. The methods are described in the next section.

Step 4: Study the existing system

Examine what is already in place: the current equipment, the building layout, the existing cabling, the internet connection, and what works and what fails. A site survey records room sizes, cable routes, power points, and the distances that will decide what cable can be used.

Step 5: Analyse and classify

Sort what was collected into functional requirements, non-functional requirements and constraints. Separate what users need from what they want, since a long wish list with no priority cannot be designed to or costed.

Step 6: Prioritise

Rank requirements as must have, should have and could have. Budget almost always forces something out, and it is better that the decision is made deliberately with the client than silently by the technician.

Step 7: Resolve conflicts

Requirements contradict each other. Finance wants the lowest cost, management wants the highest availability, users want open access and security wants it restricted. Take the conflicts back to management, who decide, and record the decision.

Step 8: Document the requirements

Write them in a requirements specification: numbered, specific, measurable, and each traceable to who asked for it.

Step 9: Validate and sign off

Take the document back to the stakeholders, confirm it says what they meant, and have it signed. This is the step most often skipped and the one that protects the technician. Without a signed specification, there is no way to show later that a complaint is a new request rather than a failure to deliver.

Step 10: Manage changes

Requirements change during a project. Record each change, its effect on cost and time, and who approved it.

Methods of Collecting User Requirements

Interviews and observation together are the strongest combination for a small organisation. Users describe the system they think they use, and observation shows the system they actually use. The difference between the two is usually where the real requirement lies.

Sample Interview Questions

• How many staff will use the network, and in which rooms?
• What do you use a computer for in a normal day?
• Which files or systems do you need to reach, and who else needs to reach them?
• What goes wrong with the current arrangement?
• Does any work need to be done from outside the office?
• What must never be accessible to everyone?
• How long could you continue working if the network went down?
• Are more staff or more branches expected in the next two years?
• What budget has been set, and over what period?

Sample Requirements Specification Entry

Each entry is numbered so it can be referred to later, states one thing only, and is written so that it can be tested on completion.

Common Errors in Requirements Collection

• Talking only to management, and never to the people who will use the network.
• Accepting vague statements such as "it should be fast" without pinning down a number.
• Letting the technician's preferred solution decide the requirements, instead of the other way round.
• Ignoring future growth, so the network is full on the day it is handed over.
• Failing to record constraints, especially the budget, until the design is already drawn.
• Skipping sign-off, which leaves every later disagreement unresolvable.

Performance Requirements

Users expect fast and reliable access to applications and data. For example, a bank's transaction processing system requires low latency and high throughput to serve customers promptly.

Scalability

Networks must accommodate future growth without costly redesigns. A growing cooperative society needs a scalable network to add new branches and users seamlessly.

Security

Protecting data from unauthorized access and cyber threats is critical. Hospitals handling patient records need robust encryption and access controls to comply with data protection laws. In Kenya, the Data Protection Act places obligations on any organisation holding personal data, and those obligations are a requirement the network must meet.

Availability and Reliability

Users require continuous network availability to avoid business disruptions. County government offices need redundant connections and backup power to maintain essential services during outages.

Ease of Use and Management

The network should be user-friendly and manageable by ICT staff with available skills. Small enterprises benefit from network designs that simplify troubleshooting and routine maintenance.

Budget

Every requirement has a cost, and the budget decides which are met. It is collected as a requirement in its own right, early, because a design drawn without knowing the budget is usually redrawn.

Chapter Summary

This chapter explored the process of designing a computer network by first understanding user needs through careful collection, analysis, and documentation. It began with an introduction to computer networking, including key terms and the various network types such as LAN, WAN, PAN, and MAN, followed by a detailed discussion of common network topologies like star, ring, mesh, hybrid, and point-to-point. The components essential to a computer network were examined, covering switches, routers, ports, computers, and transmission media. The chapter then progressed to developing both physical and logical network designs, emphasizing how these frameworks support overall network functionality. A comprehensive overview of network design was presented, highlighting methodologies such as hierarchical and flat network designs, and considerations for different site types including greenfield and brownfield environments. Site preparation was addressed through planning the network floor layout and determining data and access points. Finally, the chapter concluded with fundamental design goals focusing on scalability, availability, security, and manageability to ensure robust and efficient network performance.