ICT ch5.pptx

# Understanding the internet and its infrastructure The internet is a vast, interconnected network of computer networks that facilitates widespread information exchange. ## 1. Understanding the internet and its infrastructure ### 1.1 The internet's fundamental definition The internet, a short form of "Interconnected Network," is essentially a massive collection of interconnected computer networks. It functions as a network of networks, serving as a powerful tool for global information exchange. Each device connected to the internet is assigned a unique address, known as an IP address, and a computer name. ### 1.2 How the internet works: essential components For the internet to function, several key components are required: #### 1.2.1 Connectivity Connectivity refers to the physical links that connect devices within a network. There are two primary types of internet connectivity: ##### 1.2.1.1 Dial-up connection Dial-up connection is an older method of accessing the internet that utilizes a telephone line and a modem. This process involves the modem "dialing" a specific phone number to establish a connection with an Internet Service Provider (ISP). * **How it works:** * A modem calls a designated number through the telephone line. * During an active dial-up connection, the telephone line cannot be used for voice calls simultaneously. * **Components:** * An account with an ISP. * A telephone line connection. * A modem (which can be external or internal). * Communication software. * **Speed:** Typically limited to a maximum of 56 kilobits per second (kbps). This speed is insufficient for modern websites, video streaming, or efficient downloads. * **Features:** * Uses the Public Switched Telephone Network (PSTN). * Extremely slow by current standards. * While inexpensive, it is considered outdated. * Internet access is unavailable if the phone line is in use. ##### 1.2.1.2 Broadband connection Broadband connection represents a high-speed internet access method that is perpetually active ("always on") and does not interfere with telephone line usage. This category encompasses various technologies, including DSL, ADSL, Fiber Optic, Cable, and mobile technologies like 4G/5G. * **How it works:** * Utilizes digital signals transmitted over telephone lines, fiber optic cables, or wireless signals. * Most DSL and Fiber connections allow simultaneous internet access and phone calls. * **Speed:** Significantly faster than dial-up connections: * DSL: typically ranges from 1 to 20 Megabits per second (Mbps). * Fiber optic: can range from 50 Mbps to 1 Gigabit per second (Gbps) or higher. * 4G/5G mobile broadband: speeds can vary widely, from 10 Mbps to 1000 Mbps, depending on network conditions. * **Features:** * High-speed and always available. * Supports demanding online activities such as video streaming, online classes, cloud computing, and gaming. * Considered reliable and modern. * **Example Use Cases:** Home internet (Wi-Fi), office networks, fiber optic connections, and mobile data (3G/4G/5G). #### 1.2.2 Common language (protocols) Protocols are the rules and standards that govern how devices communicate over the internet. Two crucial protocols are TCP (Transmission Control Protocol) and IP (Internet Protocol). * **Internet Protocol (IP):** * Acts as the addressing system for the internet. * Determines the routing of data packets, specifying where they should go and how they travel between devices. * When data is sent, IP breaks it into smaller packets, adds source and destination IP addresses to each packet, and routes them through the network. * At the destination, IP reassembles the packets. * **Transmission Control Protocol (TCP):** * Works in conjunction with IP to ensure reliable data transfer. * Divides data into packets. * Attaches necessary information to each packet for reassembly at the destination and for error checking. > **Tip:** Think of IP as the postal system that routes letters to the correct addresses, and TCP as the mail tracker that ensures no letter is lost and all arrive in the correct order. ### 1.3 Internet services The internet supports a wide array of services, each designed for specific purposes: #### 1.3.1 World Wide Web (WWW) The World Wide Web is a vast collection of documents accessible via the internet. These documents can contain text, graphics, audio, and video. * **Design:** Web documents are typically designed using HyperText Markup Language (HTML). * **Access:** The web allows users to navigate information non-linearly by clicking on hyperlinks, enabling them to jump between different content. * **Characteristics:** * Non-linear navigation. * Rich media content (video, audio, text, graphics). * Interactive. * **Key Internet Terms related to the Web:** * **Web server:** A program and computer that responds to requests from web browsers. * **Webpage:** A single document on the World Wide Web. * **Web browser:** A program that allows users to view and interact with hypertext documents (e.g., Mozilla Firefox, Google Chrome). * **Homepage:** The initial webpage displayed when a user accesses a website. * **HTTP (Hypertext Transfer Protocol):** The protocol used by the web to transfer hypertext documents and other internet resources. * **URL (Uniform Resource Locator):** The complete address of a resource on the internet, specifying its exact location (e.g., `https://www.example.com/about/index.html`). #### 1.3.2 E-mail (Electronic Mail) E-mail enables users to send and receive messages, including text, audio, and video clips. It can be used for one-to-one or one-to-many communication and allows for the attachment of large documents. * **Features:** * Transmission of text, messages, audio, and video. * Supports sending to single users or groups. * Allows attachment of large documents. * Users can read, print, forward, reply to, or delete messages. * Significantly cheaper and faster than traditional communication services. * **Addressing:** Each e-mail user has a unique e-mail address for message delivery. * **Basic E-mail Terms:** * **From:** Sender's information. * **Sent:** Date and time the message was sent. * **To:** Recipient's address. * **CC (Carbon Copy):** Sends a copy of the message to additional recipients. * **Reply:** Responds to the sender of a message. * **Forward:** Sends a received message to another recipient. * **Inbox:** Stores incoming mail. * **Draft:** Stores unfinished emails. * **Trash:** Stores deleted messages. * **Sent:** Stores outgoing mail. #### 1.3.3 FTP (File Transfer Protocol) FTP is a protocol used to transfer data between computers over the internet. It allows users to send and receive files. * **Functionality:** Enables downloading files from remote computers connected to the internet. * **Example Use Case:** Uploading a website to a web server. #### 1.3.4 Telnet Telnet is a program that allows users to log into remote computers on the internet, enabling remote computer access. * **Characteristics:** * Telnet sessions are text-based, without graphical interfaces. * Requires knowing the IP address of the remote computer. * Remote login typically requires specific privileges. * **Example Command:** `telnet 192.168.1.10` #### 1.3.5 Usenet Usenet is a distributed discussion system where millions of users exchange information on a vast array of topics. * **Difference from E-mail:** Usenet messages are stored on central servers, and users must connect to these servers to read or download messages posted to specific groups. In contrast, e-mail is distributed to individual mailboxes. #### 1.3.6 Chat & Instant Messaging Chat programs and instant messaging services allow users to communicate with each other in real-time by typing messages. * **Examples:** WhatsApp, Facebook Messenger. #### 1.3.7 Search Engines Search engines respond to user queries by searching vast indexes of documents and presenting a list of matching results. * **Examples:** Google, Yahoo. --- # Internet protocols and addressing Internet protocols and addressing form the foundational system that enables data to travel across the global network. ### 2.1 The role of the Internet Protocol (IP) The Internet Protocol (IP) serves as the primary addressing system for the internet. Its core function is to ensure that data packets are correctly routed from their origin to their intended destination. #### 2.1.1 How IP handles data When you send information over the internet, such as requesting a webpage or dispatching an email, the Internet Protocol performs several key actions: * **Packet breakdown:** It divides larger pieces of data into smaller, manageable units called packets. * **Addressing:** Each packet is augmented with a header that contains crucial information, including the source IP address and the destination IP address. * **Routing:** IP is responsible for directing these packets across the network, guiding them through various interconnected devices and networks until they reach their target. * **Reassembly:** At the destination, the packets are reassembled in the correct order to reconstruct the original data. #### 2.1.2 The relationship between TCP and IP The Transmission Control Protocol (TCP) and the Internet Protocol (IP) often work in tandem to ensure reliable data transfer. * **TCP's role:** TCP is responsible for dividing the data into packets and then attaching the necessary information to ensure that these packets can be accurately reassembled at the destination and to check for any errors that may have occurred during transmission. * **IP's role:** IP then takes these packets and labels them with the appropriate destination address, sending them on their way through the network. > **Tip:** Think of TCP as the meticulous organizer who carefully prepares and checks each item before it's sent, and IP as the efficient postal service that knows exactly how to deliver each item to its correct address. ### 2.2 IP addressing Each device connected to the internet is assigned a unique address, known as an IP address, which is essential for its identification and communication within the network. --- # Common internet services and their applications This section explores the fundamental services that enable information exchange and interaction across the internet. ### 3.1 Understanding internet connectivity and protocols The internet is a vast network of interconnected computer networks that facilitates widespread information exchange. Every computer on the internet is assigned a unique address, known as an IP address, and a computer name. #### 3.1.1 Internet connectivity Connectivity refers to the physical links that enable devices to communicate on a network. There are two primary types: * **Dial-up connection:** * An older method using a telephone line and a modem to connect to an Internet Service Provider (ISP). * It requires the modem to "dial" a phone number, establishing a connection. * During a dial-up connection, the telephone line cannot be used for voice calls simultaneously. * Speeds are typically very slow, often a maximum of 56 kbps. * This speed is insufficient for modern websites, videos, or large downloads. * It utilizes the Public Switched Telephone Network (PSTN). * While cheap, it is considered outdated. * Internet access is unavailable if the phone line is busy. * Components include an ISP account, a telephone connection, a modem, and communication software. * **Broadband connection:** * A high-speed internet connection that is always on and does not tie up the telephone line. * Technologies include DSL, ADSL, Fiber Optic, Cable, and mobile broadband (4G/5G). * It uses digital signals over various mediums like telephone lines, fiber cables, or wireless transmission. * Most broadband connections allow simultaneous internet use and phone calls. * Speeds are significantly faster than dial-up, with DSL offering 1–20 Mbps, Fiber optic 50 Mbps – 1 Gbps or more, and mobile broadband ranging from 10 Mbps to 1000 Mbps. * Key features include high speed, always-on connectivity, and the capability to support demanding applications like video streaming, online classes, cloud services, and gaming. * Examples include home Wi-Fi, office internet, fiber connections, and mobile data. #### 3.1.2 Internet protocols Protocols are essential for the internet to function, acting as the common languages for communication. * **Internet Protocol (IP):** * This is the addressing system of the internet, responsible for determining data routing and travel paths between devices. * When data is sent, IP breaks it into small packets, adds source and destination IP addresses to each packet, routes them through the network, and reassembles them at the destination. * **Transmission Control Protocol (TCP):** * Works in conjunction with IP. * TCP divides data into packets, attaches necessary information for reassembly, and checks for errors to ensure data integrity. * **Tip:** Think of IP as the postal service that routes letters to the correct address, and TCP as the mail tracker that ensures all letters arrive in order and none are lost. ### 3.2 Major internet services and their applications The internet offers a variety of services for different purposes: #### 3.2.1 World Wide Web (WWW) * The World Wide Web is a vast collection of interlinked documents stored on the internet, containing text, graphics, audio, and video. * It uses HyperText Markup Language (HTML) to design web documents. * Users access information non-linearly by clicking hyperlinks, allowing them to jump between content. * The web is characterized by its rich media content and interactivity. * **Key WWW terms:** * **Web server:** A program and computer that responds to requests from web browsers. * **Webpage:** A single document on the web. * **Web browser:** A program that allows users to display and interact with hypertext documents (e.g., Mozilla Firefox, Google Chrome, Internet Explorer). * **Homepage:** The initial webpage displayed when a user accesses a web server or follows a link to it. * **HTTP (Hypertext Transfer Protocol):** The protocol used to transfer hypertext documents and other internet resources. * **URL (Uniform Resource Locator):** The complete address of a resource on the internet, specifying its exact location (e.g., `https://www.example.com/about/index.html`). * **Domain names:** Part of a URL that identifies a specific website or network. #### 3.2.2 E-mail (Electronic mail) * Email allows users to send and receive messages, including text, audio, and video clips. * Messages can be sent to single users or groups. * Users can attach large documents to their emails. * Features include reading, printing, forwarding, replying, and deleting messages. * Email is a significantly cheaper and faster communication method compared to traditional services. * Each user has a unique email address for message delivery. * **Basic email terms:** * **From:** Sender's information. * **Sent:** The date and time the message was sent. * **To:** The primary recipient(s) of the message. * **CC (Carbon Copy):** Sends a copy of the email to additional recipients. * **Reply:** Sends a response back to the sender (and potentially others). * **Forward:** Sends an existing email to a new recipient. * **Inbox:** Stores incoming mail. * **Draft:** Stores unfinished emails. * **Trash:** Stores deleted messages. * **Sent:** Stores outgoing mail. #### 3.2.3 FTP (File Transfer Protocol) * FTP is a protocol used to transfer data between computers on the internet. * It allows users to both send (upload) and receive (download) files. * **Example Application:** Uploading website files from a local computer to a web server. #### 3.2.4 Telnet * Telnet is a program that enables users to log into and control remote computers over the internet. * It provides remote computer access. * Telnet sessions are text-based, lacking graphical interfaces. * To use Telnet, the IP address of the remote computer must be known, and the user typically needs privileges to log in remotely. * **Example Command:** `telnet 192.168.1.10` #### 3.2.5 Usenet * Usenet is a global discussion system where millions of users exchange information on a wide range of topics. * It differs from email in that Usenet messages are stored on central computers (servers), and users must connect to these servers to read or download messages posted to specific newsgroups. In contrast, email messages are distributed to individual mailboxes. #### 3.2.6 Chat & Instant Messaging * Chat programs and instant messaging services allow users to communicate with each other in real-time by typing messages. * **Examples:** WhatsApp, Facebook Messenger. #### 3.2.7 Search Engines * Search engines are tools that respond to user queries by searching vast indexes of documents and displaying a list of relevant results. * **Examples:** Google, Yahoo. --- ## Common mistakes to avoid - Review all topics thoroughly before exams - Pay attention to formulas and key definitions - Practice with examples provided in each section - Don't memorize without understanding the underlying concepts

| Term | Definition | |------|------------| | Internet | A vast collection of interconnected computer networks that allows for global information exchange. It is essentially a network of computer networks, where each connected device is assigned a unique address. | | Interconnected Network | A system where multiple independent computer networks are linked together, enabling communication and data sharing between them. | | IP Address | A unique numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication. It serves as an identifier for routing and addressing. | | Connectivity | The physical or logical link that allows devices on a network to communicate with each other. It is a fundamental requirement for the internet to function. | | Dial-up Connection | An older method of connecting to the internet that utilizes a telephone line and a modem. It establishes a connection by dialing a specific phone number to reach an Internet Service Provider (ISP). | | Modem | A hardware device that modulates and demodulates signals, converting digital data from a computer into an analog signal that can be transmitted over telephone lines, and vice versa. | | Public Switched Telephone Network (PSTN) | The global network of telephone services that allows for voice calls, and was historically used for dial-up internet connections. | | Broadband Connection | A high-speed internet connection that is always active and does not tie up the telephone line. It encompasses technologies like DSL, fiber optics, cable, and mobile data. | | DSL (Digital Subscriber Line) | A technology that provides high-speed internet access by transmitting digital data over traditional copper telephone lines. | | Fiber Optic | A broadband technology that uses thin strands of glass or plastic to transmit data as light pulses, offering very high speeds and reliability. | | Internet Protocol (IP) | A set of rules governing the format of data sent over the internet. It is responsible for addressing, packet routing, and ensuring data reaches its intended destination. | | Packet | A small unit of data that is transmitted over a network. Data is broken down into packets before being sent and reassembled at the destination. | | TCP (Transmission Control Protocol) | A core protocol of the Internet Protocol suite that provides reliable, ordered, and error-checked delivery of a stream of bytes between applications running on hosts communicating via an IP network. | | World Wide Web (WWW) | A vast collection of interlinked hypertext documents and resources accessed via the internet. It is a service that uses HTTP to transfer information. | | HTML (Hypertext Markup Language) | The standard markup language for creating web pages and web applications. It uses tags to structure content and define its appearance. | | Hyperlink | A reference to data that the user can follow by clicking or tapping. It allows navigation between different web pages or resources. | | Web Server | A program and computer that stores website files and responds to requests from web browsers, delivering web pages to users. | | Webpage | A single document accessible on the World Wide Web, typically written in HTML and containing text, images, and hyperlinks. | | Web Browser | A software application used to access and display information on the World Wide Web. It interprets HTML and other web technologies to render webpages. | | URL (Uniform Resource Locator) | A web address that specifies the location of a resource on the internet, including the protocol, domain name, and path to the specific file or page. | | E-mail (Electronic Mail) | A digital messaging system that allows users to send and receive text, audio, video, and attachments over the internet. | | FTP (File Transfer Protocol) | A standard network protocol used for the transfer of computer files between a client and server on a computer network. | | Telnet | A network protocol that provides a command-line interface for remotely accessing and controlling other computers over a network. It is primarily text-based. | | Usenet | A worldwide distributed discussion system that allows users to post and read messages, categorized by topic, on various newsgroups. | | Search Engine | A software system designed to search for information on the World Wide Web. Users enter keywords, and the search engine returns a list of relevant web pages. |