<h5 id="51-introduction-to-computer-networks">5.1 Introduction to Computer NETWORKS</h5> <ul> <li>A network is a group of two or more similar things or people interconnected with each other. Examples include social networks, mobile networks, and computer networks.</li> <li>A computer network is an interconnection among two or more computers or computing devices, allowing them to share data and resources. It can include servers, desktops, laptops, and cellular phones.</li> <li>Networks can vary in size and can include networking devices like switches, routers, and modems. Devices in a network can be connected through wired media like cables or wireless media like air.</li> <li>In a communication network, data is divided into smaller chunks called packets and carried over the network. Each device that can receive, create, store, or send data to different network routes is called a node.</li> <li>Network interconnectivity allows for simultaneous information exchange through email, websites, audio/video calls, and sharing of resources like printers and networked storage. Users can connect devices through hotspots, forming small personal networks.</li> </ul> <p>======</p> <h5 id="52-types-of-networks">5.2 Types of Networks</h5> <ul> <li>Different types of computer networks exist, ranging from small networks of handheld devices to large networks of computers spread across the globe.</li> <li>Networks can be classified based on geographical area covered and data transfer rate into LAN, MAN, and WAN.</li> <li>LAN (Local Area Network) covers a small geographical area and has a high data transfer rate.</li> <li>MAN (Metropolitan Area Network) covers a larger geographical area than LAN but smaller than WAN, and has a high data transfer rate.</li> <li>WAN (Wide Area Network) covers a large geographical area and has a lower data transfer rate compared to LAN and MAN.</li> <li>Some networks are connected wirelessly, while others are connected through wires.</li> </ul> <p>======</p> <h5 id="521-local-area-network-lan">5.2.1 Local Area Network (LAN)</h5> <ul> <li>A Local Area Network (LAN) connects computers and devices in a limited geographical area, such as a room, office, or campus.</li> <li>Connectivity can be wired (Ethernet cables, fiber optics) or wireless (Wi-Fi).</li> <li>LANs are relatively secure, allowing only authenticated users to access shared resources.</li> <li>High-speed data transfer rates are a feature, ranging from 10Mbps (Ethernet) to 1000Mbps (Gigabit Ethernet).</li> <li>LANs can typically extend up to 1km, and are suitable for high-speed, short-range communication.</li> </ul> <p>As for the minimum internet speed for a video call, it depends on the quality and number of participants. However, a general guideline is 0.5-1 Mbps (Megabits per second) for both upload and download speeds.</p> <p>======</p> <h5 id="522-metropolitan-area-network-man">5.2.2 Metropolitan Area Network (MAN)</h5> <ul> <li>Metropolitan Area Network (MAN) is an extended version of LAN that covers a larger geographical area such as a city or a town.</li> <li>The data transfer rate in MAN ranges from Mbps, but it is less compared to LAN.</li> <li>Cable TV networks or cable-based broadband internet services are examples of MAN.</li> <li>MAN can be extended up to 30-40 km.</li> <li>Multiple LANs can be connected together to form a MAN.</li> </ul> <p>======</p> <h5 id="523-wide-area-network-wan">5.2.3 Wide Area Network (WAN)</h5> <ul> <li>Wide Area Network (WAN) connects computers and other LANs and MANs across different geographical locations of a country or in different countries or continents.</li> <li>A WAN can be formed by connecting a LAN to other LANs via wired or wireless media.</li> <li>Large businesses, educational and government organizations connect their different branches in different locations across the world through WAN.</li> <li>The Internet is the largest WAN that connects billions of computers, smartphones, and millions of LANs from different continents.</li> <li>WANs are used by organizations to access their data and systems located in different parts of the world.</li> </ul> <p>======</p> <h5 id="53-network-devices">5.3 Network Devices</h5> <ul> <li>A modem is a device that converts digital signals into analog signals and vice versa, enabling communication between different types of networks.</li> <li>A hub is a basic network device that broadcasts all incoming data packets to all its ports, useful for small networks with few devices.</li> <li>A switch is an advanced network device that selectively forwards data packets to specific ports based on their MAC addresses, improving network efficiency.</li> <li>A repeater is a device that amplifies and regenerates signals to extend network coverage, useful for overcoming signal attenuation in long networks.</li> <li>A router is a device that connects multiple networks and routes data packets between them based on their IP addresses, enabling communication between different networks.</li> <li>A gateway is a device that connects different types of networks and translates data packets between their protocols, enabling communication between incompatible networks.</li> </ul> <p>======</p> <h5 id="531-modem">5.3.1 Modem</h5> <ul> <li>Modem is a device used for conversion between analog signals and digital bits.</li> <li>It consists of two parts: a modulator and a demodulator.</li> <li>The modulator converts digital data into analog signals for transmission.</li> <li>The demodulator converts the received analog signals back into digital data.</li> <li>Modems are used in computers for internet connectivity, enabling digital data transmission over analog communication channels.</li> </ul> <p>======</p> <h5 id="532-ethernet-card">5.3.2 Ethernet Card</h5> <ul> <li>An Ethernet card, also known as a Network Interface Card (NIC), is a network adaptor used to set up a wired network.</li> <li>It acts as an interface between a computer and the network, and is typically mounted on the motherboard of a computer.</li> <li>The Ethernet card supports data transfer between 10 Mbps and 1 Gbps (1000 Mbps).</li> <li>Each NIC has a unique MAC address, which helps in identifying the computer on the network.</li> <li>The Ethernet cable connects the computer to the network through the NIC.</li> </ul> <p>======</p> <h5 id="533-repeater">5.3.3 Repeater</h5> <ul> <li>Signals carrying data can travel a certain distance (approximately 100 m) before losing strength.</li> <li>Beyond this limit, signals become weak and need regeneration.</li> <li>A repeater is an analog device that works with signals on connected cables.</li> <li>It regenerates weakened signals appearing on the cable and reinserts them back onto the cable.</li> <li>Repeaters help maintain signal strength over long distances, enabling data transmission over extended cable lengths.</li> </ul> <p>======</p> <h5 id="534-hub">5.3.4 Hub</h5> <ul> <li>An Ethernet hub is a network device used to connect different devices through wires.</li> <li>It has multiple ports, as shown in Figure 5.8, with 8 ports in the example.</li> <li>Data arriving on any of the lines are sent out on all the others.</li> <li>A hub’s limitation is that if data from two devices come at the same time, they will collide.</li> <li>No equations or formulae are provided in the text.</li> </ul> <p>======</p> <h5 id="535-switch">5.3.5 Switch</h5> <ul> <li>A switch is a networking device that plays a central role in a Local Area Network (LAN).</li> <li>It is used to connect multiple computers or communicating devices, and extracts the destination address from the data packet to see where to send the packet.</li> <li>A switch forwards multiple packets at the same time and drops noisy or corrupted signals, asking the sender to resend it.</li> <li>It does not send signals to all devices, but only to the selected ones.</li> <li>Ethernet switches are common in homes and offices to create LANs or to access the Internet.</li> </ul> <p>======</p> <h5 id="536-router">5.3.6 Router</h5> <ul> <li>A router is a network device that receives, analyzes, and transmits data to other networks.</li> <li>It can connect a local area network (LAN) to the internet and has advanced capabilities such as analyzing and altering data packets.</li> <li>A router can repackage data into smaller packets if necessary, allowing it to transmit data over different types of networks.</li> <li>Routers can be wired or wireless, with wireless routers providing Wi-Fi access to devices.</li> <li>Modern home Wi-Fi routers often perform the functions of a router, modem, or switch, connecting to incoming broadband lines and converting them to digital data for computing devices.</li> </ul> <p>======</p> <h5 id="537-gateway">5.3.7 Gateway</h5> <ul> <li>A network gateway is a key access point that serves as a “gate” between an organization’s network and the Internet.</li> <li>It acts as the entry and exit point of a network, routing data packets and maintaining information about internal and remote network connection paths.</li> <li>Gateways are implemented as software, hardware, or a combination of both, often integrated with a firewall at the network’s edge.</li> <li>For simple Internet connectivity at homes, the gateway is usually the Internet Service Provider.</li> <li>A router is typically configured to work as a gateway device in computer networks, receiving and routing data packets between networks.</li> </ul> <p>======</p> <h5 id="54-networking-topologies">5.4 Networking Topologies</h5> <ul> <li>A network topology refers to the arrangement of devices and peripherals in a network.</li> <li>Common types of network topologies include mesh, ring, bus, star, and tree.</li> <li>In a mesh topology, every device is connected to every other device.</li> <li>A ring topology involves connecting each device to two other devices, forming a circular network path.</li> <li>In a bus topology, all devices share a common communication line, while a star topology has all devices connected to a central hub or switch.</li> <li>A tree topology is a combination of bus and star topologies, forming a hierarchical structure.</li> </ul> <p>======</p> <h5 id="541-mesh-topology">5.4.1 Mesh Topology</h5> <ul> <li>In a mesh topology, each device is connected with every other device, allowing for large traffic handling and reliability even in the case of a node failure.</li> <li>This topology is more secure than others, as different data is carried on each cable.</li> <li>However, it has complex wiring and high cabling costs due to many redundant connections.</li> <li>The number of wires required for a fully connected mesh topology of $n$ nodes is $n(n-1) /> 2$.</li> <li>Mesh topology is less prone to network congestion because multiple nodes can transmit data simultaneously.</li> </ul> <p>======</p> <h5 id="542-ring-topology">5.4.2 Ring Topology</h5> <ul> <li>In ring topology, each node is connected to two other devices, forming a circular network.</li> <li>The data transmission in ring topology is unidirectional, allowing data to move in one direction only.</li> <li>Each node in the ring topology acts as a repeater, amplifying and retransmitting the signal.</li> <li>If a node fails, the entire network is affected, making ring topology less fault-tolerant.</li> <li>The token-ring protocol is commonly used in ring topology, where a token (special frame) is passed around the network for data transmission.</li> </ul> <p>======</p> <h5 id="543-bus-topology">5.4.3 Bus Topology</h5> <ul> <li>In bus topology, each device connects to a transmission medium (bus) and data is passed on to the bus, allowing it to be received by any node.</li> <li>A single backbone wire, called the bus, is shared among nodes, making it cost-effective and easy to maintain.</li> <li>However, bus and ring topologies are considered less secure and reliable.</li> <li>If a node fails in bus topology, data transmission continues unaffected, but locating the issue can be challenging.</li> <li>In a ring topology, if one node fails, the entire network can be affected, causing communication to halt until the issue is resolved.</li> </ul> <p>======</p> <h5 id="544-star-topology">5.4.4 Star Topology</h5> <ul> <li>In star topology, all devices are connected to a central node, which can be a hub or a switch.</li> <li>This configuration allows for fast and efficient communication between devices and the central node.</li> <li>If one device experiences issues, it does not affect the rest of the network, but failure in the central device can cause network-wide problems.</li> <li>The central node can function as a broadcasting or unicast device, depending on network needs.</li> <li>In a broadcasting setup, data is sent to all nodes, while a unicast setup allows the node to identify and forward data to the destination node only.</li> </ul> <p>======</p> <h5 id="545-tree-or-hybrid-topology">5.4.5 Tree or Hybrid Topology</h5> <ul> <li>The Tree or Hybrid topology is a hierarchical network structure, combining elements of star, ring, and bus topologies.</li> <li>It is often utilized in Wide Area Networks (WANs) to connect multiple Local Area Networks (LANs).</li> <li>These LANs can take the form of ring, bus, or star topologies themselves.</li> <li>A centralized device first receives data from the source, then distributes it through every branch, which can contain additional nodes.</li> <li>An example of this topology is depicted in Figure 5.16, showing 4 star topologies connected in bus formation.</li> </ul> <p>======</p> <h5 id="55-the-internet">5.5 The Internet</h5> <ul> <li>The Internet is a global network of computing devices, including desktop, laptop, servers, tablets, mobile phones, peripheral devices like printers, scanners, and smart electronic appliances like TV, AC, refrigerator, fan, etc.</li> <li>It consists of networking devices such as routers, switches, gateways, and is ever-evolving with increasing smart devices like drones, vehicles, door lock, security camera, etc.</li> <li>Computers are connected to a modem through a cable or wirelessly (Wi-Fi), which then connects to a local Internet Service Provider (ISP), forming a regional and national network, and eventually the Internet backbone.</li> <li>It is a widespread network, impacting society through increased use of online tools for education, creativity, entertainment, socialization, and e-commerce.</li> <li>The Internet’s reach extends beyond technical fields, with its influence being used by everyone in the society.</li> </ul> <p>======</p> <h5 id="56-applications-of-internet">5.6 Applications of Internet</h5> <ul> <li>The World Wide Web (WWW) is a system of interlinked hypertext documents that are accessed via the Internet.</li> <li>Electronic mail (Email) is a method of exchanging messages between people using electronic devices.</li> <li>Chat, also known as online chat or instant messaging, is a form of real-time communication between two or more people.</li> <li>Voice Over Internet Protocol (VoIP) is a technology that allows for the placing and receiving of phone calls over the Internet.</li> </ul> <p>======</p> <h5 id="561-the-world-wide-web-www">5.6.1 The World Wide Web (WWW)</h5> <ul> <li>The World Wide Web (WWW) or web is an ocean of information comprising trillions of interlinked web pages and resources.</li> <li>It was invented by Sir Tim Berners-Lee in 1990, who defined three fundamental technologies for its creation: HTML, URI, and HTTP.</li> <li>HTML (HyperText Markup Language) is a language used to design standardized web pages for global access. It uses tags to define the display of page content.</li> <li>URI (Uniform Resource Identifier) is a unique identifier for a web resource, specifying its location or name. URL, a type of URI, provides the location and mechanism to access the resource.</li> <li>HTTP (HyperText Transfer Protocol) is a set of rules for retrieving linked web pages across the web, with HTTPS being its more secure and advanced version.</li> </ul> <p>======</p> <h5 id="562-electronic-mail-email">5.6.2 Electronic Mail (Email)</h5> <ul> <li>Email, short for electronic mail, is a method of sending/receiving messages via the Internet.</li> <li>It can be sent to multiple recipients, with options for carbon copy (CC) and blind carbon copy (BCC).</li> <li>Users can create, save drafts, and attach files to emails. Emails can also be forwarded and printed.</li> <li>Features include filtering spam, organizing emails in folders, and managing contact lists.</li> <li>Email services can be obtained from various providers, or through customized business addresses.</li> </ul> <p>======</p> <h5 id="563-chat">5.6.3 Chat</h5> <ul> <li>Chatting or Instant Messaging (IM) over the Internet is a real-time communication method through text messages.</li> <li>It allows multiple people to discuss common interests and individuals to send messages instantly.</li> <li>With increasing internet speed, various formats like images, documents, audio, and video can be sent.</li> <li>This enables audio and video calls, as well as group chats or calls.</li> <li>Popular IM applications include WhatsApp, Slack, Skype, Yahoo Messenger, Google Talk, Facebook Messenger, and Google Hangout.</li> </ul> <p>======</p> <h5 id="564-voip">5.6.4 VoIP</h5> <ul> <li>VoIP, or Voice over Internet Protocol, is a technology that allows for voice calls over the Internet, also known as Internet Telephony or Broadband Telephony.</li> <li>It converts analogue voice signals into digital data, which is then transmitted over a broadband line.</li> <li>VoIP has two major advantages: it is cost-effective, with many services being free or very cheap, and it offers increased portability and functionality, allowing calls to be made and received from any location with Internet access.</li> <li>VoIP calls can be received and made using IP phones, and incoming calls can be automatically routed to the VoIP phone when connected to the Internet.</li> <li>The main disadvantage of VoIP is that call quality is dependent on Internet connection speed, with slow connections leading to poor voice call quality.</li> </ul> <p>======</p> <h5 id="57-website">5.7 Website</h5> <ul> <li>A website is a collection of webpages under one domain name, related by a common theme and template.</li> <li>It contains information organized in multiple pages about an organization or a particular purpose/theme.</li> <li>Websites are saved on a web server, and navigated by clicking on hyperlinks.</li> <li>To access a website, the URL (address of the website) is typed in the browser’s address bar.</li> <li>The home page of the website is displayed upon pressing enter.</li> </ul> <p>======</p> <h5 id="571-purpose-of-a-website">5.7.1 Purpose of a Website</h5> <ul> <li>A website’s purpose is to make information accessible to people, with examples including companies advertising or selling products, and government organizations publishing circulars or getting feedback.</li> <li>Websites should be user-friendly, transparent, and designed with specific categories of people in mind.</li> <li>Common purposes for creating websites include selling products/services, posting/finding information, communication, entertainment, and disseminating content/software.</li> <li>User experience is crucial, aiming to provide information to users with minimal effort.</li> <li>An activity involves visiting a website (e.g., NCERT, SWAYAM) and noting specific page URLs.</li> </ul> <p>======</p> <h5 id="58-web-page">5.8 Web Page</h5> <ul> <li>A web page is a document on the World Wide Web (WWW) viewed in a web browser, created using HTML and CSS.</li> <li>It is typically part of a website, contains information such as text, images, audio, video, software applications, and interactive contents.</li> <li>Web pages are made attractive and organized with various styling and formatting.</li> <li>Scripts like JavaScript, Python, and PHP are used to define the behavior of a web page on different actions, making it interactive.</li> <li>Each web page has a unique address, and the first page of a website is called a home page, which contains information and links to all related web pages.</li> </ul> <p>======</p> <h5 id="581-static-and-dynamic-web-pages">5.8.1 Static and Dynamic Web Pages</h5> <ul> <li>A web page can be static or dynamic.</li> <li>Static web pages have constant content, no additional processing is performed, and they are written in HTML, JavaScript, and/or CSS.</li> <li>Dynamic web pages have content that can be different for different users, and it can change frequently.</li> <li>Dynamic web pages are created using languages such as JavaScript, PHP, ASP.NET, Python, Java, Ruby, etc.</li> <li>They are more complex and take more time to load than static web pages as they may perform additional processes like getting information from the database.</li> <li>Examples of dynamic web pages include those displaying the date, time, weather report, or having e-commerce applications.</li> </ul> <p>======</p> <h5 id="59-web-server">5.9 Web Server</h5> <ul> <li>A web server is a system that stores and delivers website content to clients such as web browsers.</li> <li>It can be both hardware and software. As hardware, it stores web server software and a website’s contents. It needs to be connected to the internet for accessibility.</li> <li>As software, it is a specialized program that understands URLs and responds to browser requests. It is assigned a unique domain name for access.</li> <li>To develop and test a website, a web server needs to be installed on a personal computer.</li> <li>The web browser sends an HTTP request for a page with desired data or service. The web server accepts, interprets, searches, and responds with an HTTP response, displaying the requested web page or an error message.</li> </ul> <p>======</p> <h5 id="510-hosting-of-a-website">5.10 Hosting of a Website</h5> <ul> <li>Web hosting is a service that allows websites to be put on the Internet and made accessible to users worldwide.</li> <li>This is done by uploading website files (HTML, CSS, JavaScript, images, databases, etc.) onto server resources rented from a cloud service provider.</li> <li>Web hosting service providers offer paid services for using server resources such as RAM, hard disk, bandwidth, etc., which can be increased or decreased as needed.</li> <li>Web servers, whether local or cloud-based, are assigned a unique IP address that needs to be mapped to a textual domain name for user access.</li> <li>Domain names must be registered (purchased) with an authorized agency for website access using a browser (URL).</li> </ul> <p>======</p> <h5 id="5101-how-to-host-a-website">5.10.1 How to host a website?</h5> <ul> <li>Select a web hosting service provider that offers required features, technologies, and services.</li> <li>Identify and register a suitable domain name through a domain name Registrar.</li> <li>Create logins with appropriate rights, and note down the IP address to manage web space.</li> <li>Upload files in organized folders on the allocated space.</li> <li>Get domain name mapped to the IP address of the web server using the Domain Name System (DNS).</li> </ul> <p>======</p> <h5 id="511-browser">5.11 Browser</h5> <ul> <li>A browser is a software application that enables users to view web pages and retrieve data from web servers.</li> <li>Commonly used web browsers include Google Chrome, Internet Explorer, Mozilla Firefox, and Opera.</li> <li>Modern web browsers can display interactive and dynamic websites, unlike early versions like Mosaic, which only supported static websites.</li> <li>Advanced security features in modern browsers include encryption and cookies for storing browser settings and data.</li> <li>Mozilla Firefox is an open-source web browser that is free to download and use.</li> </ul> <p>======</p> <h5 id="5111-browser-settings">5.11.1 Browser Settings</h5> <ul> <li> <p>Web browsers have settings that define their behavior, including privacy, search engine preferences, download options, auto signature, autofill and autocomplete feature, theme, etc.</p> </li> <li> <p>In Mozilla Firefox, access the Menu button, then select Options to display the Preferences and Options window.</p> </li> <li> <p>The General Panel allows setting the default browser, language, downloading files and applications, Firefox update settings, and browsing and network settings.</p> </li> <li> <p>The Home Panel sets the home page of the browser and browser window and tab settings.</p> </li> <li> <p>The Search Panel edits settings of the search engine used by Firefox.</p> </li> <li> <p>The Privacy and Security Panel secures the browser and data with options like enhanced tracking protection, forms and passwords, history and address bar, cookies and site data, permission to view pop-ups windows and install add-ons.</p> </li> <li> <p>The Sync Panel sets up and manages a Firefox account for accessing all services provided by Mozilla.</p> </li> </ul> <p>======</p> <h5 id="5112-add-ons-and-plug-ins">5.11.2 Add-Ons and Plug-ins</h5> <ul> <li>Add-ons and plug-ins are tools that extend and modify the functionality of a browser.</li> <li>Plug-ins are complete programs or third-party software, such as Flash and Java, that can be used by the browser for multiple functionalities and even by other applications.</li> <li>Add-ons, also referred to as extensions, are not complete programs and are used to add only a particular functionality to the browser.</li> <li>Add-ons are installed by clicking the Options button on the top right corner of the browser and selecting the Addons option.</li> <li>Plug-ins are installed by clicking the Plug-ins options on the left side of the browser window and making the desired selections to enable or disable the required plug-ins.</li> </ul> <p>======</p> <h5 id="5113-cookies">5.11.3 Cookies</h5> <ul> <li>A cookie is a text file containing information transferred by a website to a user’s browser, stored in the browser as a text file.</li> <li>Cookies help recognize users, identify visited pages, and remember choices made during browsing, customizing displayed information such as language preference or shopping preferences.</li> <li>They enable features like auto-login and display personalized advertisements based on user interests.</li> <li>While generally harmless, cookies can’t access hard disk information or transmit viruses, but viruses can be disguised as cookies and cause harm.</li> <li>Users can disable cookies through their browser’s Privacy and Security settings.</li> </ul> <p>======</p>