Computer network - this is nothing likea combination of several computers among themselves, allowing them to exchange data. Global networks are called when they cover users from all over the world. Note that the first computer networks of civil purpose appeared in the United States. But few know that the very principle of this technology was first used in the USSR, and thanks to this, once the first missile defense system was created.
Today there is a fairly wide classification of networks. According to territorial prevalence, global, local and regional computer networks are distinguished. Global computer networks networks are located on the territory of thestate or several states, for example, the worldwide Internet network. Local networks cover the territory within a few tens of square meters, and regional networks are located in the territory of the region or city.
However, the two main terms in the classification of networks are: WAN and LAN.
WideAreaNetwork (WAN) - global computer networks covering large regions, which include local networks and other telecommunications devices and networks.
LocalAreaNetwork (LAN) - local networks thathave a closed infrastructure prior to their access to service providers. The very term "LAN" is able to describe both a small office network and a network of a large factory that covers a few hundred hectares.
The oldest global network is the Internet. It provides different ways to connect remote computers and the general use of information resources and distributed services.
Initially, global computer networkswere engaged in solving the problem of accessing various remote terminals and computers to powerful computers called host-s. These connections were made using unswitched or switched channels of telephone networks or using satellite dedicated data networks, for example, working on the X.25 protocol.
To connect to such networks were usedmodems that operated under specialized telecommunications programs, such as COMIT, PROCOM, BITCOM, MITEZ, etc. Managed MS-DOS, they exchanged information with the computer to which the connection was established.
The very construction of a global network it is not difficult to describe. A global network consists of cells, which are local networks. In turn, local networks consist of smaller networks and individual computers. Here such a multi-level hierarchy provides the construction of a network. In addition, each device on the network must have its own IP address or unique identifier.
Nowadays, there are fewer and fewercomputers that are part of global computer networks. Basically, these are home PCs. For the most part, network subscribers are those computers that are included in local computer networks, therefore, most often experts are working out options for how best to ensure the interaction of several local computer networks. It is necessary at the same time to provide for the remote computer connection with any computer entering the remote local network, or vice versa. The latter option is very relevant when increasing the number of home and personal computers.
Now as a network equipmentuse switching centers, which are for X.25 networks the specialized devices of the manufacturers of Telenet, Ericsson, Siemens, Alcatel, etc., but for networks with TCP / IP, routers of Decnis and Cisco are used. However, technologies do not stand still, and it is likely that in the future we will see an even more effective organization of a global network, which today has a huge impact on the lives of almost everyone.