Guided and Unguided Network Systems

Welcome to an exciting journey into the world of network systems.

Learning about these foundational networking topics is crucial for understanding how modern technology works and how it shapes our world. Networking enables the interconnection of computer-based devices to share information and resources, forming the backbone of communication in nearly every industry. Servers and clients illustrate the dynamic roles within a network, with servers providing services and clients requesting them. The design of a network, or its architecture, defines how devices interact and ensures efficient communication. Peer-to-peer networks and decentralisation highlight alternative models of resource sharing and control, empowering innovation without reliance on central authorities. Understanding communication protocols and scalability is essential for designing systems that can grow and adapt to increasing demands, which is critical in fields like technology, business, and digital infrastructure. These concepts are not just technical—they underpin how we connect, collaborate, and innovate in the modern world, making them valuable for any future career path.

You will now dive deep into how information travels between devices in Client/Server and Peer-to-Peer networks, as well as the difference between guided (wired) and unguided (wireless) communication systems. By the end of this section, you will:

1. Understand the various network systems and how they work.

2. Explore the communication technologies, protocols, and standards that power the internet and networks.

3. Gain practical knowledge to appreciate how these systems connect the world around us.

You will not only learn the theory but also get a chance to think critically, solve problems, and work in teams to solidify your knowledge. These life skills will empower you to better understand the networks you use every day.

Get ready to uncover the fascinating world of network communication—a skillset for today’s connected world.

KEY IDEAS

• Architecture: The design and structure of a network, which defines how devices and components interact.

• Client: A hardware or software on a network that makes requests to a server.

• Communication: The exchange of data or information between devices within a network using protocols.

• Decentralisation: The distribution of network functions or control across multiple devices or nodes, without relying on a central authority.

• Network: Interconnection of computer-based devices to share information and resources.

• Peer-to-Peer Network: A decentralised network model where devices (peers) share resources and communicate directly without a central server.

• Scalability: The ability of a network or system to handle growth, such as adding more devices or increasing traffic, without performance degradation.

• Server: A hardware or software on a network that provide services to clients.

Computer network often simply referred to the collection of computers and computer-based devices interconnected by communication channels that facilitate communications and allow sharing of resources and information among interconnected devices.

Activity 4.1 Client and server In order to recap on a previously covered topic, watch the following video:

Network Topologies - N10-008 CompTIA Network+ : 1.2 In small groups get together and answer the following questions

1. Explain what a network topology is.

2. Explain how does understanding network topologies contribute to effective network design and troubleshooting?

3. Identify one network topology that uses a server.

4. Explain your findings to the group.

Architecture and Functionality of Client/

Server Network

The client-server model is a distributed framework where clients request resources or services, and servers provide them by the services requested. This model is designed for centralised resource management, scalability, and efficient handling of multiple client requests.

In networking, a client, such as a computer, smartphone, or software application, initiates a request for services from a server. The server, being a powerful central machine or program, processes these requests and provides the necessary services to the intended client. The Figure 4.1 below shows the architecture of Client/Server Network.

Figure 4.1: Sample of Client-Server Architecture

Table 4.1: Architecture of client/server network Architecture of Client/Server Network Server Client 1 A central machine or set of machines that provide services, resources, or data to clients.

Devices or programs that make requests to the server for services or resources.

2 Typically, powerful in terms of processing power, storage, and reliability.

Generally, less powerful than servers but optimised for user interaction and network communication.

Table 4.2: Functionality of client/server network Functionality of Client/Server Network Client Server 1 A client initiates communication by sending a request to the server.

The server processes the request and sends back an appropriate response, such as data retrieval, resource access, or the execution of a command to the intended client 2 Clients rely on the server for access to shared resources, which makes management easier.

Servers manage resources centrally, allowing for better security, control, and updates.

Table 4.3: Layers of Client-Server Model

Presentation Layer Application Layer Data Layer

Purpose This layer is responsible for the user interface and interaction. It is the layer where users interact directly with the application.

This is the core of the architecture where the business logic is processed. It acts as an intermediary between the client and data layers.

The data layer is where the data is stored, managed and retrieved.

It provides a mechanism for data storage.

Components Includes the software or applications that run on the client devices, such as web browsers, mobile apps, or desktop applications.

The application servers that process data, enforce business rules, and make decisions based on user input.

Databases, data storage systems, or data management tools.

Functionality Displays information to the user.

Sends user requests to the server.

Receives and formats data received from the server for display.

Processes client requests.

Applies business rules (e.g., processing a transaction, verifying login credentials).

Coordinates data retrieval or updates by interacting with the data layer.

Stores and manages data (e.g., user information, transactions, and product details).

Responds to requests from the application layer to retrieve, update, or delete data.

How Client-Server Model Network Works

₁. The computer-based devices, including the clients and the server must be connected to a network.

2. The client sends various requests to the server in order to submit, retrieve, or modify the data located on the server. For example, Client “A” with an IP address of 192.168.0.1 may send a request to the server to print a file with a printer connected on the network.

3. The server then processes each client request and provides services to the intended clients. From the example stated in point “2”, the server will provide services to the client by allowing the printer to print the intended file for the client.

The three basic layers to client-server architecture Client-server architecture typically consists of three basic layers, known as the three- tier architecture. These layers separate different functions of the application to improve scalability, manageability and flexibility.

Types of Client-server Architecture

1-Tier Architecture 1-Tier Architecture, also known as Single-Tier Architecture, is the simplest form of application architecture where all components of the application (presentation, application logic, and data management) reside in one place, usually on the same machine or device.

2-Tier Architecture This consists of a direct communication link between the client and the server. The main components involved are the client which is the user interface or application that requests services or data; and the server that processes requests and provides the required services or data to the client. In this type of architecture, the client directly communicates with the server without an intermediary. This setup is straightforward and suitable for small-scale applications where the client sends a request, and the server processes it and returns the response.

3-tier architecture In the 3-tier architecture, the client communicates with the application layer, which processes the request using business logic and interacts with the data layer if needed.

The application layer returns the result to the client. For example, we use the user interface of a smartphone apps to interact with the app while an application server executes most of the app’s code and a database server stores the data.

From the above explanation, we could see that the application in 3-tier architecture is divided into three separate layers:

1. Presentation Layer (Client): This is the front end where the user interacts on the network (e.g., web browser, mobile app).

2. Application Layer (business logic layer): It contains the business logic and also processes client requests (e.g., web server, application server).

3. Data Layer (Database Server): It manages data storage and retrieval of the network.

N-tier architecture The N-tier architecture expands on the 3-tier architecture by adding more layers for better distribution of tasks and load balancing. The client communicates through multiple intermediary layers before reaching the data layer, which improves modularity and allows for specialised services. The additional layers may include,

1. Client Layer: User interface.

2. Web Server Layer: Handles HTTP requests and responses.

3. Application Server Layer: Processes the business logic.

4. Database Layer: Data storage and management.

5. Additional Layers: Security services, load balancers or caching layers.

Advantages

1. Centralised file storage makes it easier for multiple clients to share, store and operate on files.

2. Centralised databases improve data organisation, security and management.

3. Server scalability allows for easier hardware and performance management as well as cost savings.

4. Device management is more effective when done from a single server instead of individual clients.

Disadvantages

1. It is easier to infect a single server than individual clients.

2. Since centralised servers store the software and data, users lose all access if those servers fail.

3. Too many client requests can overload the server, causing performance issues and service outages.

4. Buying and running a server and networking equipment is an additional expense.

Peer-to-Peer (P2P) Networks

Peer-to-peer (P2P) network is a group of computers connected to each other directly whereby each of them acts as a node for sharing files within the group. Each computer acts as the server for the files instead of having a central server to act as a shared drive.

This means the computers serving as the clients again serve as the servers since there is no central server.

Figure 4.2: Peer to peer Network From Figure 4.2, a peer-to-peer (P2P) network is a type of decentralised network where each participant (or “peer”) has equal privileges and responsibilities unlike the traditional client-server model. P2P networks do not rely on a central server, instead, each device in the network acts as both a client and a server, sharing resources directly with other peers.

Key Feature of Peer-to-Peer Network

1. Decentralisation: There is no central authority or server managing the network;

each peer can initiate or complete tasks.

2. Resource Sharing: Peers share resources such as files, processing power, or bandwidth.

3. Direct Communication: Peers communicate directly with each other, without intermediate servers.

4. Dynamic Connectivity: Peers can join and leave the network as needed without affecting the overall network’s functionality.

5. Scalability: P2P networks can scale as more peers join since each additional peer adds more resources to the network.

Activity 4.2 Group discussion on network models Having gone though both client-server network and peer to peer network models, make a deep reflection on the two network models in terms of connectivity, components, storage and functionalities.

1. In groups of four to five, differentiate between the two types of network model according to the specification in the table below.

2. State the reasons why you will choose peer to peer network over client-server network.

3. Outline the challenges that may be associated with client-server computer network.

Table 4.4: Network models SN. Specification Peer-to-Peer Network Client-server Network 1 Components 2 Network structure 3 Connection 4 Storage 5 Functionality Advantages of Peer-to-Peer Network

1. Decentralisation: No central server which makes the connection easier as compared to Client-server network.

2. Cost-Effective: Reduces the need for expensive central servers.

3. Scalability: Easily expands as more peers join, adding resources and capacity.

4. Resource Sharing: All peers contribute resources, improving overall network efficiency.

5. Resilience: Continues functioning even if some peers go offline.

Disadvantages of Peer-to-Peer Network

₁. Security Risks: Harder to manage and protect against malware or data breaches.

2. Inconsistent Performance: Network speed depends on the peers’ availability and resources.

3. Limited Control: Difficult to monitor and manage compared to a centralised network.

4. Data Duplication: Risk of multiple copies of data across peers, leading to inefficiency.

5. Search Inefficiency: Locating specific resources can be slower in unstructured networks.

Table 4.5: Summary of the differences between Peer-to-peer network and client-server network Aspect Peer-to-Peer Network Client-server Network Structure Decentralised, no central server Centralised, with dedicated servers Components All nodes act as both clients and servers Distinct clients and servers Storage Distributed across peers Centralised on servers Mode of Connection Direct connections between peers Clients connect to a central server Scalability High, as each new peer adds resources Limited by server capacity Control Limited, hard to manage Centralised control and easier management Reliability Resilient to single-node failures Dependent on server reliability Security More challenging to secure Easier to secure due to centralised control Performance Variable based on peers’ resources More consistent, server-dependent Resource Sharing Peers share resources directly Server provides resources to clients

Table 4.6: Summary of the similarities between Peer-to-peer network and client-server network Aspect Peer-to-Peer Network Client-server Network Purpose Facilitates data/resource sharing between devices Facilitates data/resource sharing between devices Connectivity Requires network connectivity for communication Requires network connectivity for communication Communication Support sending and receiving data Support sending and receiving data Device Interaction Devices communicate and share resources Devices communicate and access resources Network Protocols Use common network protocols (e.g., TCP/IP) Use common network protocols (e.g., TCP/IP)

Activity 4.3 Configuration of peer-to-peer network Working in small groups, discuss configuration of a peer-to-peer network involving four workstations.

1. List the materials that may be needed to configure or build the intended network.

2. State the two ways the workstations can be connected.

3. Demonstrate how you will connect the four workstations using “Ethernet cable” with RJ45 using end-to-end approach.

4. Discuss your approach with the entire class.

5. What additional resource(s) will you need when you want to configure the same four workstations on client-server network?

P2P (Peer-to-Peer) Network Architecture is a decentralised model where each participant, or “peer,” in the network acts as both a client and a server. Unlike traditional client-server architecture, there is no central server that manages resources or mediates interactions. Instead, each peer has equal responsibilities and capabilities, enabling direct communication and resource sharing between nodes.

In this network model, any node or computer in a Peer-to-Peer network can communicate with any other node, sharing files or data according to permissions.

Activity 4.4 Key features of P2P network

1. Pair with your colleague.

2. Review the following video - What is a P2P network I NordVPN

3. Reflect on how peer-to-peer network works and discuss the key features of it as spelt out in the table below.

4. Share your finding with another group.

Types of P2P

1. Pure P2P Network

In a pure P2P network, there is no central server or authority. Every peer is equal and has the same role in the network. Each peer acts as both a client and a server, sharing and requesting resources directly from others. Example: Early versions of Gnutella, where all nodes have equal responsibilities and there is no reliance on a central server for coordination.

2. Structured P2P Network

A structured P2P network uses a defined architecture and algorithms to organise and search for data efficiently. It usually uses technologies such as Distributed Hash Tables (DHT) to map data to specific peers, making searches more predictable and faster. Example: Kademlia and Chord, which use DHTs to organise peers and data.

3. Hybrid P2P Network

It is a combination of the P2P model and client-server model. While peers still share resources among themselves, a central server is used for specific functions such as indexing or connection management. The central server helps improve the efficiency of searching and coordinating peers, but the data is still shared directly between peers.

Example: BitTorrent, which uses a central tracker server to help peers find each other, but the actual data transfer is peer-to-peer.

4. Unstructured P2P Network

In this type of network, peers are connected randomly without any predefined structure. Searching for data is less efficient because a search may require flooding the network with requests. However, it allows for more flexibility in terms of peer participation. Example: Early versions of Napster and Kazaa, where peers did not have a structured way of organising data or connections.

5. Permissioned P2P Network

It is a semi-private P2P network where peers must have authorisation to join. These networks often use cryptographic methods to ensure secure access and participation. It combines aspects of security and decentralisation, suitable for enterprise or specialised use cases. Example: Some blockchain networks like Hyperledger Fabric, where only authorized nodes can participate in data exchange.

Table 4.7: Types and key features of P2P network and their examples Type of Network Key feature Example Pure P2P Network Fully decentralised, no central server Early Gnutella Hybrid P2P Network Central server for coordination, P2P data sharing BitTorrent Structured P2P Organised with algorithms for efficient search Kademlia, Chord Unstructured P2P Random peer connections, flexible participation Early Napster, Kazaa Permissioned P2P Requires authorisation, secure access Hyperledger Fabric Key Applications of P2P Networks ₁. P2P removes the middleman between users, allowing for applications such as file-sharing, social networking, messaging and even financial transactions.

2. P2P networks are widely used for sharing large files directly between users without a central server. Examples: Early versions of Skype for voice and video calls.

3. P2P networks allow multiple computers to share their processing power to solve complex problems collaboratively.

4. P2P networks are used to distribute video and audio streams directly among users, reducing server dependency. Examples: PeerTube for video streaming and P2P live streaming platforms.

Activity 4.5 Key Features of P2P network In small groups, complete the table below, you will then present your findings to the rest of the class.

Table 4.8: Activity on the key features of P2P network SN. Specification How it works 1 Control or authority 2 Resource Sharing 3 Communication 4 Storage 5 Scalability

Ethernet was invented by Robert Metcalfe, a researcher at Xerox PARC (Palo Alto Research Center) in 1973. He developed the idea as a way to connect multiple computers and devices within a local network to share data.

In 1976, Metcalfe, along with his team at Xerox, published a landmark paper titled “Ethernet: Distributed Packet-Switching for Local Computer Networks.” This paper laid the groundwork for Ethernet’s framework, using a coaxial cable and a method called Carrier Sense Multiple Access with Collision Detection (CSMA/CD) to manage data transmission and avoid packet collisions. The original Ethernet operated at a speed of 2.94 Mbps

Figure 4.3: Coaxial cable Figure 4.4: Twisted pair cable Between 1980s-1990s, Ethernet technology moved from the original coaxial cables to twisted-pair cabling (e.g., Cat5, Cat6 cables) and fibre optics, improving flexibility and performance.

Over the years, Ethernet speeds improved significantly ₁. 10 Mbps in the 1980s (standard 10BASE-T)

2. 100 Mbps (Fast Ethernet) in the 1990s

3. 1 Gbps (Gigabit Ethernet) in the early 2000s

4. 10 Gbps and beyond with advancements to 40 Gbps and 100 Gbps for specialised applications.

Activity 4.6 Ethernet Cabling

Video - https://www.youtube.com/watch?v=2oNq6Gtyf7M

1. Watch the above video and split into small groups

2. You will be allocated one of the ethernet cable types.

3. Research the cable that you were allocated and identify speeds, length, advantages/disadvantages to that particular type of cable.

4. Create PowerPoint slide to present this information

5. Present this to the rest of the class.

Data Communication Models

Data communication models describe how data is transmitted between devices or systems over a communication medium. These models establish a framework that outlines the process and protocols for reliable communication. The two most widely known models are the OSI Model and the TCP/IP Model. Both of these models break down the communication process into layers to simplify the task of networking and ensure compatibility between devices.

Computer Network models Computer Network Models is the structured frameworks that show how computers and devices communicate with each other across a network. These models define layers of operations, the protocols used in communication, and the services provided at each layer.

Types of Computer Network Models

There are two computer network models i.e. OSI Model and TCP/IP Model on which the whole data communication process relies

Figure 4.5: Types of Network

Communicating on a Network using the TCP/IP suite Communicating over a network using the TCP/IP suite involves a structured framework that allows devices to send and receive data across interconnected networks, including the internet.

The TCP/IP (Transmission Control Protocol/Internet Protocol) suite operates in four main layers, each with distinct roles as show below;

Figure 4.6: TCP/IP Network Model

1. Application Layer

This is the top layer where user interaction occurs. It provides services for applications to communicate over a network. The main function of the application layer is to prepare data for transmission by formatting it and adding necessary headers. Protocols like Hypertext Transfer Protocol for web browsing, File Transfer Protocol for file transfers and Simple Mail Transfer Protocol for emails are common examples of application layer.

2. Transport Layer

This layer is responsible for ensuring data transfer is reliable and error-free. TCP (Transmission Control Protocol) segments or UDP (User Datagram Protocol) are created here, adding a transport layer header to the data.

The main protocols of the transport layer are:

a. TCP (Transmission Control Protocol): A connection-oriented protocol that ensures reliable data transfer with error checking, acknowledgment of received packets and data retransmission if necessary.

b. UDP (User Datagram Protocol): A connectionless protocol that is faster but does not guarantee delivery, used for applications where speed is more critical than reliability (e.g., streaming, online gaming).

3. Internet Layer

This layer is responsible for logical addressing and routing of data across networks.

In this layer, each device on the network has a unique IP address that identifies it and again routers forward packets based on IP addresses, ensuring data reaches its destination. The main protocol here is the Internet Protocol (IP), which defines IP addresses and helps route packets between the source and destination across different networks.

4. Network Access/Link Layer

This layer handles physical data transfer between network devices, managing how data is placed on the network medium (e.g., cables, wireless signals). The data is broken into frames with link-layer headers and sent to the physical medium for transfer. In this layer, protocols like Ethernet or Wi-Fi determine how data frames are transmitted over physical networks.

Summary of the function of the TCP/IP Protocol

1. TCP (Transmission Control Protocol) ensures reliable, ordered data delivery and provides flow control, error detection, and correction.

2. IP (Internet Protocol): Responsible for addressing and routing packets to their destination. Defines IP addresses and packet structure.

3. The TCP/IP protocol is essential because it ensures end-to-end Communication between devices across different networks and interoperability of devices from different manufacturers. It is scalable and supports a large and growing number of devices on the Internet, and it is flexible.

The Open System Interconnection Model

The open systems interconnection (OSI) model is a conceptual model created by the International Organisation for Standardisation which enables diverse communication systems to communicate using standard protocols. The OSI model is a way of sub- dividing a communications system into smaller parts called layers. The Open System Interconnection model is made in layers architecture, which allows easy data communication as each layer has predefined structured and functionalities.

Figure 4.7: TCP/IP Network Model

The Functions of the Layers

1. The Physical Layer: This is where the actual connection happens. It involves cables, switches, and signals that carry data from one device to another. Think of it as the roads for data to travel on.

2. The Data Link Layer: This layer organises data into chunks called “frames” and checks for errors as data moves from one device to another. It is like a traffic controller making sure data goes where it is supposed to without collisions.

3. The Network Layer: The Network Layer is third from bottom in OSI model and is responsible for establishing data communication channel between multiple networks or devices or hosts or nodes. This layer finds the best path for data to travel between devices. It uses something like addresses called “IP addresses” to help data know where it is going, similar to how GPS helps find directions.

4. The Transport Layer: This layer breaks data into smaller parts (packets) and ensures they reach their destination correctly. It also checks if any packets are lost along the way and resends them. Imagine it as the postal service, making sure each letter arrives.

5. The Session Layer: This layer sets up, manages, and ends conversations or “sessions” between devices. It is like setting up a phone call and making sure both sides are ready to talk and hanging up when done.

6. The Presentation Layer: This layer changes data into a format that applications can understand (like converting languages). It also helps keep data safe through encryption. Imagine it as a translator or data protector.

7. The Application Layer: This is the layer that users interact with directly. It includes apps like web browsers, email, and games. Think of it as the place where we see and interact with the internet and other networked services.

The OSI Model is the most widely used computer network models which come with some major advantages which makes it so popular.

Advantages of OSI Models

1. Easy Troubleshooting: By dividing networking into layers, it makes it easier to pinpoint and fix problems in specific areas.

2. Promotes Compatibility: It helps different devices and systems work together, even if they come from different manufacturers.

3. Better Learning: The model helps students and professionals understand how networks work by breaking down complex tasks.

Disadvantages of OSI Model

1. Too Complicated: With seven layers, it can be overwhelming and unnecessary for smaller networks.

2. The model is mostly theoretical and does not always match real-world networks that follow simpler models like TCP/IP.

3. Can be Costly: Implementing a network to strictly follow the OSI Model can require extra equipment and software, raising costs.

Activity 4.7 Importance of the OSI Model

Think pair share: Reflect on the OSI model and how each layer works.

1. Identify any three importances of this type of Network model.

2. Why do you think this network model is widely used?

3. As an ICT student, explain the benefits you will derive from learning about this type of network model.

4. In spite of the numerous advantages in OSI model, list any three setbacks associated with this network model.

HTTP and HTTPS Protocols

HTTP (Hypertext Transfer Protocol) and HTTPS (Hypertext Transfer Protocol Secure) are both protocols used for transferring data between a web server and a web browser.

Let us take some few minutes to explore how each works.

Hypertext Transfer Protocol (HTTP)

HTTP is the foundation of data communication for the World Wide Web. It allows web browsers and servers to communicate and exchange information such as web pages, images, and other web content.

How It Works

HTTP works as a request-response protocol. The browser (client) sends a request to the server, which then responds with the requested data (e.g., an HTML page). One of the characteristic features of HTTP is that it does not encrypt the data being transmitted, making it vulnerable to interception and eavesdropping.

Hypertext Transfer Protocol Secure

HTTPS is an extension of HTTP and is used for secure communication over a computer network. It is essential for transmitting sensitive data like login credentials, payment information, and other private data. HTTPS provides an encrypted and secure connection, protecting data integrity and user privacy. HTTPS has security features such as:

1. Encryption: Prevents unauthorised access to the data being transmitted.

2. Authentication: Verifies the identity of the website, ensuring that users are communicating with the intended server.

3. Data Integrity: Ensures that the data is not altered during transmission.

How It Works

HTTPS uses Secure Sockets Layer (SSL) or Transport Layer Security (TLS) protocols to encrypt the data between the client and server. This encryption ensures that even if the data is intercepted, it cannot be read without the proper decryption key.

Activity 4.8 Group work the differences between HTTP and HTTPS

1. Put yourselves into small groups.

2. Reflect on how HTTP and HTTPS work considering their purposes, port used, security and how they work.

3. You can also explore more information from the internet on the differences between HTTP and HTTPS.

4. Indicate the differences between HTTP and HTTPS in the table below based on the various key components specified in the table.

Table 4.9: Group work on the differences between HTTP and HTTPS Features Hypertext Transfer Protocol Secure Hypertext Transfer Protocol Purpose Security Port used How it works

5. Explain your discussions to the rest of the class as a group.

SMTP (Simple Mail Transfer Protocol) is a standard protocol used for sending and relaying email messages over the internet. It is one of the essential protocols in the TCP/IP suite that supports email communication. The primary function of SMTP is to transfer outgoing emails from the sender’s email client to the mail server and from one server to another until it reaches the recipient’s mail server. SMTP is a push protocol, meaning it pushes email from the client to the server or between servers.

The Structure of the SMTP Message Format

The SMTP message format is structured to ensure that email communication follows a standardised protocol, facilitating consistent and reliable message delivery. An SMTP message consists of two main parts: the header and the body. But within these, there are other features in the structure as shown below.

1. Envelope: Holds the basic information about who is sending the email and who will receive it.

2. Header: Includes important details like who the email is from, who it is going to, the subject, and the date it was sent. The header section contains crucial information that helps route and process the email correctly. Some key header fields include:

a. From: Specifies the sender’s email address.

b. To: Specifies the recipient’s email address.

c. Subject: A brief description of the content of the email.

d. Date: The date and time when the email was sent.

e. CC (Carbon Copy): Additional recipients who will receive a copy of the email.

f. BCC (Blind Carbon Copy): Recipients who will receive a copy of the email without being visible to other recipients.

g. Message-ID: A unique identifier for the email, often generated by the sending mail server.

h. Reply-To: Indicates where replies to the email should be directed, which can differ from the “From” address.

3. Body: This is the main part of the email that contains the actual message or content.

4. Command and Response Interaction: The email program and the server talk to each other using special commands and responses.

5. Commands: These are instructions like HELO/EHLO (saying hello), MAIL FROM (showing who the sender is), RCPT TO (showing who the recipient is), DATA (sending the message), and QUIT (ending the session).

6. Responses: The server replies to these commands with numbers and messages to show if things are working (e.g., 250 OK means all is good; 550 No such user means there is a problem with the recipient).

Activity 4.9 Think pair share on features of mail header Having just spent time discussing Email headers, in small groups complete the following.

1. Reflect on how the common headers of a compose window work.

2. In the table below state the function of each of the headers as specified in the table.

3. Compare your finding in the table with your partner.

Table 4.10: Think pair share on features of mail header Key feature Function To CC Bcc Subject How SMTP Works

1. Starting the Connection: The email program connects to the SMTP server to begin sending the message.

2. Introduction: The program introduces itself to the server by sending a “hello” message using commands called HELO or EHLO.

3. Sharing Details: The program tells the server who is sending the email (MAIL FROM) and who will receive it (RCPT TO).

4. Sending the Message: The program sends the actual content of the email (using the DATA command), which includes both the subject and the main message.

5. Closing the Connection: Finally, the program finishes by sending a command called QUIT, which ends the session and disconnects from the server.

FTP Overview

FTP (File Transfer Protocol) is a standard network protocol used for transferring files between a client and a server over a TCP/IP network, such as the internet. It is one of the oldest protocols designed for file sharing and still commonly used for uploading or downloading files from servers. Primarily, FTP allows users to transfer files (documents, images, programs, etc.) from one computer to another securely or publicly over a network.

Extension activity Collaborative project on files downloading and up- loading FTP is the commonly used protocol used to upload and download files unto and from the internet. Use the existing groups, perform the following tasks:

1. Differentiate the difference between downloading and uploading as used in internet environment.

2. Demonstrate the appropriate steps to upload pictures to an internet platform such as Facebook or Instagram and also download an existing image from the same platform onto your computer.

3. Discuss where the downloaded files can be located on your computer.

4. Discuss what makes the uploading and downloading of the pictures possible.

How FTP works

1. Connection Establishment: FTP uses two separate connections:

a. Control Connection: Maintains the communication between the client and server for commands and responses.

b. Data Connection: Transfers the actual files between the client and server.

2. Ports Used:

a. Port 21 is used for the control connection (command and response exchange).

b. Port 20 is used for the data connection in active mode.

3. Modes:

a. Active Mode: The client opens a port and waits for the server to connect for data transfer.

b. Passive Mode FTP Passive Mode is an alternative to Active Mode that helps make file transfers more firewall friendly. This simply means that, it can operate smoothly without triggering security alarms or being stopped by the firewall.

FTP Commands and Responses

Common Commands:

1. USER: It specifies the username for authentication.

2. PASS: It specifies the password for authentication.

3. LIST: It lists the files and directories on the server.

4. RETR: It retrieves (downloads) a file from the server.

5. STOR: It uploads or sends a file to the server.

6. QUIT: This command ends the session and disconnects the client from the server.

7. Responses: FTP servers respond to commands with numeric codes and messages (e.g., 220 Service ready, 331 Username okay, need password, 550 Requested actions not taken).

Real-World Applications

₁. Website Management: FTP is commonly used to upload files to a web server when managing websites.

2. File Sharing: Used in businesses and organisations to share large files that might be too large for email attachments.

3. Backups: Utilised for backing up data from one system to a remote server.

Limitations of FTP

1. Lack of Encryption: Basic FTP does not encrypt data, making it less secure for sensitive information.

2. Firewall Issues: FTP’s active mode can be blocked by firewall, which is why passive mode is often used to solve this problem.

3. User Authentication: Requires a username and password, but without encryption, these can be intercepted.

Wireless Communication Technologies

It is a communication technology which enables the transmission of data without physical connections, using electromagnetic waves. These technologies are foundational for mobile communications, internet access, and the connection of devices in various fields like IoT (Internet of Things) and smart homes. The most significant wireless communication technologies include:

1. Wi-Fi (Wireless Fidelity)

This allows devices to connect to the internet or a local network wirelessly. It uses radio waves, typically at 2.4 GHz, 5 GHz or even 6GHz frequencies, to create wireless local area networks (WLANs). It is mostly used in home and office internet access, public hotspots and device-to-device communication.

2. Bluetooth It facilitates short-range data transfer between devices. It operates at the 2.4 GHz frequency band to connect devices like headphones, keyboards and smartphones over short distances (up to about 100 meters for newer versions). It is mostly used to connect wireless peripherals (headphones, mice), file sharing and connecting smart devices.

3. Cellular Network

It provides wide-area communication for mobile phones and devices. They are used in mobile phone services, data communication, and remote device connectivity.

4. NFC (Near Filed Communication)

This supports close-range data exchange between devices (a few centimetres apart).

It uses magnetic field induction to enable communication between two NFC-enabled devices. It is often used in contactless payments, digital ticketing and sharing small amounts of data between devices.

5. Infrared (IR) Communication

This transmits data using infrared light waves over short distances. It requires line- of-sight between devices and has a limited range. This technology is used in remote controls, simple data transfers between close devices.

6. Satellite Communication

This transmits data over long distances using satellites in Earth’s orbit. It signals are sent from an Earth station to a satellite, which then relays the signal to another station or directly to user devices. The common devices which use satellite communication technology are GPS, satellite TV, satellite phones and global internet access in remote areas.

Table 4.11: Summary of wireless communication technologies Technology/ Standard Description Transmission Medium Frequency Range Uses Wi-Fi (IEEE 802.11) A family of wireless networking protocols Ultra-high frequency (UHF) radio waves 2.4/5/6 GHz.

100m (indoors), 300m (outdoors) Primarily used for local area networking (LAN) of devices LTE (Long Term Evolution) A standard for wireless broadband communica- tion for mo- bile devices.

Ultra-high frequency (UHF) radio wave 700-2600 MHZ Several kilometres depending on cell tower density Mobile internet, VoLTE (Voice over LTE) application Bluetooth Short-range wireless technology standard for exchanging data over short distance.

ultra-high frequency (UHF) radio wave 2.4 GHz Typically, up to 10 metres (Class 2), up to 100 metres (Class 1) Used to connect peripheral devices (e.g.

keyboards, mice), audio devices or file transfer. Can also be used to share internet between different devices.

IrDA (Infrared Data

Association) A standard for wireless communi- cation using infrared light Infrared light 850 nm to 900 nm Spectrum.

Up to 1

metre Remote controls and short-range data transfer between devices.

This is very rarely used due to low speed and line of sight requirement.

RFID (Radio Frequency

Identifica- tion) A technolo- gy that uses electromag- netic fields to automatically identify and track tags attached to objects Radio Low frequency of (125134 kHz), high frequency (13.56 MHz) or ultrahigh frequency (860960 MHz) Passive tags have a range of several metres whilst active tags have tens of metres Inventory tracking, access control, and contactless payments NFC (Near Field Com- munication) A set of com- munication protocols for communica- tion between two electron- ic devices over a short distance Electromagnet- ic induction 13.56 MHz up to 10 cm Contactless payments (in EPOS systems), access control, data exchange between devices.

Satellite Internet

Satellite inter- net is a wire- less internet service that uses satellite communica- tion to deliver broadband speeds to remote areas.

Data is sent to and from satellites orbiting the Earth.

Satellite signals Ku-band (12–18 GHz), Kaband (26.5– 40 GHz), C-band (4– 8 GHz) Global (thousands of kilome- tres) Remote areas, rural connectivity, emergency services, maritime and aeronautical internet access

Activity 4.10 Collaborative project on protocols/standards and their ad- vantages and limitation

1. Organise yourselves into small groups. Each group will be allocated one of the protocols covered in the lesson

2. Research the protocol using the following guiding prompts:

a. When was it created and who created it?

b. What is it used for?

c. Advantages and limitations in using it

d. Any other interesting facts

3. Create a PowerPoint and present this to the rest of the class for feedback and discussion.