6.4. Transmission of information on the Internet. Addressing system

On the Internet, by analogy with local computer networks, information is transmitted in the form of separate blocks, which are called packets. In the case of a long message, it should be divided into a certain number of blocks. Any of these blocks consists of the address of the sender and recipient of the data, as well as some service information. Any data packet is sent over the Internet independently of the others, and they can be transmitted by different routes. After the packets arrive at their destination, the original message is formed from them, that is, the packets are integrated.

The Internet uses three types of addresses:

1) IP address - the main network address assigned to each computer at the entrance to the network. To indicate an IP address, four decimal numbers are used, separated by dots, for example, 122.08.45.7. In each position, each value can vary from 0 to 255. Any computer connected to the Internet has its own unique IP address. Such addresses can be divided into classes according to the scale of the network to which the user is connected. Class A addresses are used in large public networks. Class B addresses are used in medium-sized networks (networks of large companies, research institutes, universities). Class C addresses are used in networks with a small number of computers (networks of small companies and firms). We can also distinguish class D addresses intended to refer to groups of computers and reserved class E addresses;

2) domain address - a symbolic address that has a strict hierarchical structure, for example, yandex.ru. In this kind of address, the top-level domain is indicated on the right. It can be two-, three-, four-letter, for example:

• com - commercial organization;

• edu - educational institution;

• net - network administration;

• firm - private firm, etc.

On the left in the domain address server name is used. The transfer of a domain address to an IP address is performed automatically using a domain name system (Domain Name System - DNS), which is a method of assigning names by transferring responsibility to a network group for a subset of their names;

3) URL (Universal Recourse Locator) - a universal address that is used to designate the name of each storage object on the Internet. This address has a specific structure: data transfer protocol: // computer name / directory / subdirectory /. /file name. An example of a name is http://rambler.ru/doc.html.