Network technical means represent various electronic devices providing combination of computers in the computer network (a cable, switchboards, concentrators (Hab), servers, routers);
Network software ensure correct network functioning, exercise program control network functioning and the interface with the end user (a network operating system, the software of management of a network);
For providing a reliable communication in the course of exchange of information between subscribers of a computer network transport protocols serve. It is known that quality of information transfer in many respects by the used communication line. For example, the switched telephone channels of public networks are characterized by rather level of hindrances. When using similar channels in networks it is necessary to take additional measures on a of reliability of data transmission. In turn, fiber-optical of communication are characterized by the low level of hindrances. In this case to use the minimum set of transport services and the protocol of exchange of information. Transport protocols are of particular importance in computer networks, the transferring environment of the is characterized by rather high level of mistakes and low reliability of data transmission.
The computer network represents the set of computers, and also various electronic systems and devices connected to computers, providing management and exchange of information between computers in a network without any intermediate carriers of information. It follows from this that the main purpose of computer computer networks in that to simplify and accelerate process of interaction between end users, i.e. clients of a network, and also the organization of access for users to the general network resources.
Because of complexity of communications between systems and needs of observance of various communication requirements protocols are agreed on modular levels. Each level carries out concrete function for the located higher than a level.
At this variety of characteristics and devices of various networks rules by which all making networks will interact with each other are necessary and with other networks these rules represent the protocol of interaction in a network. Management of interaction of processes in computer networks just is also carried out on means of network protocols and the software of management of a network. Let's dwell on concept of network protocols.
Channel level provides the organization of the necessary of blocks of data and their transfer, management of streams between adjacent knots, identification of terminal points of channel, detection and corrections of mistakes, the notification about errors which are not corrected at the channel level.
For coordination of various computer networks network and transport levels among themselves are generally used. Now two main approaches to formation of a gateway : this association of networks within the Internet network according to the IP protocol and association of networks of switching of packages (X.2 according to MKKTTX.7
Computer networks happen different types: for example on their scale and the territory they are subdivided into local (LAN) and global (WAN), on the level of the organization: peer and on the basis of the server, on information transfer speed on low - average and high-speed, as connection: on coaxial, on twisted couple, fiber-optical, with information transfer on a radio channel and in the infrared range, on topology of a network i.e. structure of communications between its basic functional elements: star, tire, ring.
Network level among the main services carries out an of final points of network connections, the organization of network, management of streams of blocks of data, ensuring delivery of blocks of data, detection of mistakes and formation of about them, separation of network connections.
The fourth, transport level (level of through transfer) for data transmission between two interacting open systems and the organizations of procedure of interface of subscribers of a network from data transmission. At this level interaction of workstations — a source and the addressee of data is defined, the logical channel (transport connection between will be organized and.