Computer Networks – Notes

Computer Networks Notes and Important Points

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.

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