Notes

•  A computer network is an interconnection among two or more computers or computing devices. 
•  A computer network allows computers to share data and resources among each other. 
• Networking devices are used to connect multiple computers in different settings
• In a communication network, each device that is a part of a network and that can receive, create, store or send data to different network routes is called a node. 
• Based on the geographical area covered and data transfer rate, computer networks are broadly categorised into LAN (Local Area Network), MAN (Metropolitan Area Network) and WAN (Wide Area Network). 
• LAN is a network that connects a variety of nodes placed at a limited distance ranging from a single room, a floor, an office or a campus having one or more buildings in the same premises. 
• Ethernet is a set of rules that decides how computers and other devices connect with each other through cables in a LAN. 
• Metropolitan Area Network (MAN) is an extended form of LAN which covers a larger geographical area like a city or a town. 
• Cable TV network or cable based broadband internet services are examples of MAN. 
• Wide Area Network (WAN) connects computers and other LANs and MANs, which are spread across different geographical locations of a country or in different countries or continents.
• The Internet is the largest WAN that connects billions of computers, smartphones and millions of LANs from different continents. 
• Modem stands for ‘Modulator Demodulator’, is a device used for conversion between electric signals and digital bits. 
• Ethernet card, also known as Network Interface Card (NIC card in short) is a network adaptor used to set up a wired network. 
• Each NIC has a MAC address, which helps in uniquely identifying the computer on the network.
• A repeater is an analog device that regenerate the signals on the cables to which it is connected.
• A switch is a networking device used to connect multiple computers or communicating devices.
• A router is a network device that can receive the data, analyse it and transmit it to other networks.
•  Gateway serves as the entry and exit point of a network, as all data coming in or going out of a network must first pass through the gateway in order to use routing paths.
• The arrangement of computers and other peripherals in a network is called its topology.
• Common network topologies are Mesh, Ring, Bus, Star and Tree.
• In mesh topology each communicating device is connected with every other device in the network.
• In ring topology, each node is connected to two other devices, one each on either side. 
• In bus topology, a single backbone wire called bus is shared among the nodes, which makes it cheaper and easy to maintain. 
• In star topology, each communicating device is connected to a central networking device like a hub or a switch.
• In tree or hybrid topology, there are multiple branches and each branch can have one or more basic topologies like star, ring and bus.
• The MAC address, also known as the physical or hardware address, is a unique permanent value associated with a network adapter called a NIC. It is used to physically identify a machine on the network. 
• IP address, also known as Internet Protocol address, is a unique address that can be used to uniquely identify each node in a network.
• Unlike MAC address, IP address can change if a node is removed from one network and connected to another network.
• The Internet is the global network of computing devices.
• The World Wide Web (WWW) or web in short, is an ocean of information, stored in the form of trillions of interlinked web pages and web resources. 
• Sir Tim Berners-Lee — a British computer scientist invented the revolutionary World Wide Web in 1990. 
• HTML (HyperText Markup Language) is a language which is used to design standardised Web Pages so that the Web contents can be read and understood from any computer.
• URI (Uniform Resource Identifier) or URL (Uniform Resource Locator) is a unique address or path for each resource located on the web.
• HTTP – The HyperText Transfer Protocol is a set of rules which is used to retrieve linked web pages across the web. The more secure and advanced version is HTTPS.
• Each computer server hosting a website or web resource is given a name against its IP address. These names are called the Domain names or hostnames.
• Conversion of the domain name of each web server to its corresponding IP address is called domain name resolution. It is done through a server called DNS server.