In a computer network to ensure compatibilitylevels of the network architecture, special standards are used, which are called protocols. They are hardware and software. Hardware devices (interfaces) support standards at the physical level, and at the data level they work with special software support.
Local and global networks are determined by the fact,what protocols they use. In a local network, computers use a set of standards that is uniform for all network participants, and they connect computers of a building, a building, a floor.
Global networks usually cover large areas. They combine both individual computers and local networks using different protocols.
The activities of civilized society inmodern conditions is impossible without the means of rapid communication and the rapid exchange of information. Global networks are designed to solve this problem. The main condition for the operation of these networks is the instantaneous transfer of information, no matter how far the computers are removed from each other.
A global network is a network thatincludes computers located in huge territories with an unlimited number of computer systems included in the network. The data transfer speed in such a network is lower than in the local network.
Computer network protocols
Global networks are supported by protocolsTCP / IP, ATM, MPLS and some others. The most common protocol is TCP / IP, which includes subprotocols. It is an applied subprotocol, transport, network, channel and physical.
Most programs run at the application level and have their own protocols. This is HTTP, WWW, etc. Protocols are responsible for visualization and display of the information sought.
A transport protocol ensures the delivery of data to a specific application that can process it. It's called TCP.
The IP network protocol is responsible for receiving and sending requests to a lower level to obtain all the necessary information.
The channel and physical layers are responsible for determining the methods and conditions for the transmission of information.
Known global networks:for example, WWW (WorldWide Web). The network consists of servers that store the information necessary for users, and individual computers that receive information from servers and upload it to them. The WWW network is convenient and easy to use.
Global networks include a subnet consisting ofsuch separate components as communication lines and switching elements. Communication lines are otherwise called channels or backbones, the data moves from machine to machine.
The switching elements used to connect the communication lines are routers. These are specialized computers.
Global networks mainly contain a large number of telephone lines and cables that connect a pair of routers.
The second possibility is to connect each otherrouters is a radio link using satellites or terrestrial repeaters. Each router has its own antenna, due to which it is able to receive and send a signal. Network routers can easily receive signals from the satellite, and in some cases, they are able to hear the transmitted information of neighboring routers sending data to the satellite. In separate global networks, all routers are connected to each other by an ordinary two-point subnet, and only some of them are provided with a satellite antenna. Satellite networks are broadcasters and are most in demand where broadcasting is necessary.
