Tuesday, April 2, 2013


  Externally the Internet is similar to a telephone or cable network. However way of connection a bit different.

   At a call by phone, the device a direct line connects to station, the station attaches a wire going to other station, and that in turn connects a wire going to phone to which the call was addressed. Rigid physical connection of two called points (for example, And and B) in space turns out. Its main inconvenience – your phone is attached to the socket. If you take the device and include in the socket on other wire, to you nobody will be able to phone since other socket is any more A point (and With, for example).

   In what transmission of messages on the Internet differs from it, after all the computer at first too connects to station?

   The message sent to the Internet is coded by the computer in a series of electric signals and marked with special codes of the recipient and the sender, as though the electronic letter (package) with the direct and return address as a result is formed. From the computer the letter arrives on the server, the server verifies the address of the recipient with the special address table and, having defined the server next to it on the way to necessary the party, sends the letter there. This procedure repeats until the package won't reach the addressee. Computers of the recipient and the sender physically can be anywhere. On the Internet they are defined by IP addresses.

  Therefore the Internet doesn't connect subscribers a continuous electric wire, it codes messages in packages and transfers them from station to station. Such way of connection is called logical. It certainly more slowly, than a physical way of connection by transfer of a telephone signal, but all the same a package reaches in other point of the world for fractions of a second. The answer comes in the same way, and we communicate, without noticing a delay.

   The logical way of communication has indisputable advantages. For example, the route of the letter can pass on any connections which were free. For example, if on any line there was a malfunction or strong loading of a network, two subscribers living on one continent can communicate through another, without suspecting about it. It is more than that, the package can leave through Australia, the answer to come through Africa, and the following letter to go any the third way.

   Now in the Internet network all known communication lines from low-speed telephone lines to high-speed digital satellite and fiber-optical channels are used practically. The operating systems used in the Internet network, also differ a variety. The majority of computers of the Internet network work under Unix family OS.

   Actually Internet consists of a set of the local and global networks, to belonging various companies and the enterprises, connected among themselves various communication lines. Internet can be imagined in the form of a mosaic of the various size put from small networks which actively interact among themselves, sending files, messages, etc.

   Now the Internet is the global computer network which task, as well as any other computer network, is a data transmission from one computer to another.

   The main Internet property consists that if in a network the new subscriber is connected, information of all network becomes available to it. And, on the contrary, information and resources of its computer becomes available to all other subscribers of Internet.

  Feature of the Internet network is that actually Internet as the global world computer network, has no owner, i.e. it to whom doesn't belong. Though separate computer networks which are connected to Internet, have the specific owners.

   Internet is based on idea of existence of a set of independent networks of any architecture. It is possible thanks to application, so-called, the principle of openness of network architecture. It is that Internet doesn't show any specific requirements to connected computer networks. The consumer himself defines a type of own network and a method of its technical realization. I.e. he can choose any configuration of a network and any software. Thanks to it, practically all networks which function in the world, can be connected to Internet freely.

No comments:

Post a Comment