Computer network

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Computer networks Computer networks (English, network) is a set of the personal computer distributed in some territory and interconnected for sharing of resources . Today in the world there are more than 130 million computers and more than 80% from them are united in various information networks - from small local networks at offices, to global networks. Global networks

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Types of computer networks Local networks – connections of the computers located at small distances from each other. Regional networks – combinations of computers and local networks for expansion of a common problem of regional scale. Corporate networks – associations of local networks within one corporation. Global networks – combinations of the computers located at remote distance for the general use of world information resources. Local networks

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Local networks Local networks are systems of the interconnected computers working within one room, the building, one organization. Usually they cover the rooms which are located at small distances within the building and therefore them call local (local). 90% of information circulating in them - information of the local organization.

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Global networks Servers of global networks provide access to other computers registered on them, access to information, program resources, e-mail, computer conferences not only the to users possibility of work with information outside the computer, opening access to resources of remote cars. One of types of global networks is the Internet. The Internet – system which objects are computer networks.

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Topology There is an infinite number of ways of connection of computers. Network topology – a geometrical form and a physical arrangement of computers in relation to each other. The topology of a network allows to compare and classify various networks. Distinguish three main types of topology: Star; Ring; Tire.

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Topology "STAR" Topology "Star" - the scheme of connection at which each computer is connected to a network by means of a separate connecting cable. One end of a cable connects to a nest of the network adapter, another is connected to the central device called by the concentrator.

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Topology "RING" This topology represents consecutive connection of computers when the last is connected with the first. The signal passes on a ring from the computer to the computer in one direction. Each computer works as the repeater, strengthening a signal and transferring him is farther.

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"TIRE" topology At creation of a network according to the tire scheme each computer joins the general cable on which ends terminators are established. The signal passes on a network through all computers, being reflected from final terminators.

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Communication channels Interaction of objects of a network (servers and clients) it is carried out on communication channels for which use different physical environments. Communication channels can be compared to transport systems of freight or passenger traffic. Through computer networks information is transported. Wednesdays in which there is a communication of computers of a network, define means of connection of computers. If it is the Wednesday demanding telecommunication, communication happens on telephone wires.

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Characteristics of communication channels 1. Speed of data transmission (capacity), is measured by number of the bits of information transferred on a network in one second; 2. Capacity – the greatest possible volume of the transmitted data in one second on communication channels. 3. Reliability (ability to transfer information without distortions and losses) 4. Cost. 5. Development reserves

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Protocols In order that other computer understood information transferred one computer, it was necessary to develop the uniform rules of data transmission called by protocols. At their development all problems of communication were considered and standard algorithms of delivery of information were developed. The protocol of transfer establishes the agreement between the interacting computers. In order that process of communication took place, it is necessary to supply computers with addresses. Due to the numerous tasks which have to be solved according to the standard, distinguish a miscellaneous types protocols of data transmission, correction and correction of mistakes and other. On the Internet the international protocol of TCP/AP accepted in the seventies works.

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Thank you for attention!