A computer network is a collectionof interconnected computers andotherdevices which are able to communicatewith each other and share hardwareand software resources.The term interconnected meansthat there exists a path throughwhich data can be transmitted fromone computer / device to another.
• Information Sharing• Hardware Sharing•Software Sharing•Time efficient• Cost saving
Network of Communicating devices (Computer, Phone, MP3/MP4Player, Camera etc.) in the proximity of an individual.Covers an area of a few meters radius.Can be set up using guided media (USB cable) or unguided media(Bluetooth, Infrared).
Network of computing/Communicating devices inA room,A building, orA campus.Covers an area of a few meters to a few kilometres radius.Usually contains a single LAN, or sometimes one building can contain a fewsmall LANs (Like some schools have independent LANs in each computer lab.).Can be set up using guided media or unguided media.If a LAN is setup using unguided media, it is known as WLAN (wireless LAN).
Network of computing/communicating devices within a city.Covers an area of a few kilometres to a few hundred kilometres radius.A network of schools, or banks, or Government offices etc., within a city, areexamples of MANs.All types of communication media (guided and unguided) are used to set up aMAN.Typically owned and operated by a single entity such as a government body ora large corporation.
Network of computing/communicating devices crossing the limits of a city,country, or continent.Covers an area of over hundreds of kilometre radius.A network of ATMs, BANKs, National Government Offices, InternationalOrganizations Offices etc., spread over a country, continent, or covering manycontinents are examples of WANs.All types of communication media (guided and unguided) are used to set up aWAN.The best known example of a WAN is the internet.
A Topology is an arrangement of physical connectionsamong nodes in a network.A Node is a device, which is directly connected to acomputer network. It can be a computer or any otherdevice like printer, scanner etc.
In bus topology all the nodes are connected to a main cable calledbackbone. If any node has to send some information to any other node, itsends the signal to the backbone.A small device called terminator is attached at each end of the backbone.When the signal reaches the end of backbone, it is absorbed by theterminator and the backbone gets free to carry another signal.
In star topology each node is directly connected to a hub/switch. If anynode has to send some information to any other node, it sends the signal tothe hub/switch. In the case of a switch the signal is sent only to the intendednode(s). Star topology generally requires more cable than bus topology.
Tree topology is a combination of bus and star topologies. It is used tocombine multiple star topology networks. All the stars are connectedtogether like a bus. This bus-star hybrid approach supports futureexpandability of the network
A ring network is a network topology in which each nodeconnects to exactly two other nodes, forming a singlecontinuous pathway for signals through each node - aring. Data travels from node to node, with each nodealong the way handling every packet..
A network protocol is a set of rules for communication amongnetworked devices.Protocols generally includes rules of how and when a device cansend or receive the data, how is the sent data packaged, and how itreaches its destination.There are a number of protocols defined for computer networks.Some of them are :• File transfer protocol (FTP) – used to transmit files.• Simple mail transfer protocol (SMTP) – used to transmit e-mail messages.• Post office protocol (POP) – allows the recipient to retrievemessages.• Wireless application protocol – enables wireless devices toaccess and use the Internet using a client/server network.
Other than the transmission media many other devices are required to formcomputernetworks. Some of these devices are:• NIC : Network Interface Card is a device that enables a computer to connect to anetwork and communicate.• Hub : A Hub is an electronic device that connects several nodes to form a networkandredirects the received information to all the connected nodes in broadcast mode.
• Switch : A Switch is an intelligent device that connects several nodes to form anetwork and redirects the received information only to the intended node(s).• Repeater : A Repeater is a device that is used to regenerate a signal which is on itswaythrough a communication channel. A repeater regenerates the received signaland re-transmits it to its destination.• Gateway : A Gateway is a device, which is used to connect different types ofnetworks and perform the necessary translation so that the connected networks cancommunicate properly.
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