General information about the global Internet. Training course program computer networks and telecommunications Basic information about the Internet

Literally translated into Russian, the Internet is an internetwork, i.e. it's an amalgamation of networks. Now the Internet is a worldwide CS.

The Internet is a unique collection of LAN, MAN, WAN that are connected together.

The basis of the Internet is the ARPANET network, developed in 1969 with funds from the Defense Advanced Research Projects Agency (DAPRA). The ARPANET was the result of research to create networks that would be strong enough to function in wartime. Despite the fact that the ARPANET network was created with military money, it was developed mainly in universities. Some parts of it were classified, but most of it was open because... maximum possibility and ease of use of the network d.b. make it more stable, more reliable, more sustainable, more accessible, more useful.

One of the first standardized services was email, followed by a standard for file transfer, and then a standard for newsgroups. None of these services were developed for commercial or private use. All of this was done by people interested in creating open standards that anyone could use.

The main group that oversees the development of the Internet is the Internet Society ISOC. ISOC oversees many voluntary groups: the Architects Group, the Engineering Forces, the Research Forces, the Numerical Internet Control Group, the Disaster Relief Committee, the Internet Action Forum, etc. But there is no single authoritarian figure on the Internet; senior officials may . on networks connected to the Internet. Nobody pays for the Internet in general. Everyone pays for their part.

Host is a node PC that performs centralized support functions for this network, making programs and data files available to other PCs on the Internet.

A protocol is a set of semantic and syntactic rules and procedures that determine the operation of functional devices in the communication process.

A dedicated channel is a communication channel to which data processing terminal devices are constantly connected and does not require switching.

A switched channel is a communication channel for subscribers, to which the connection is made through general-purpose telephone channels by dialing the subscriber's number on a telephone dialer. This creates a temporary connection.

The true birthday of the Internet was 1983, when revolutionary changes occurred in computer communications software. In 1983, the TCP/IP communication protocol was standardized.

TCP/IP (Transmission Control Protocol over Internet Protocol) is a transmission control protocol over the Internet Protocol. This is a common protocol for all Internet PCs. It is software that allows individual parts of the Internet to work together to form a single network. The TCP/IP protocol does not depend on hardware and cable connection networks.

TCP/IP is a combination of two standards (stack): TCP and IP, which play different roles in the process of communication over the Internet. IP defines a low-level method for moving information from one PC to another, TCP provides a high-level method for determining the presence of information and checking for its correctness (I-book, IP pages, and TCP-language).

TCP Tasks:

1) Ensuring guaranteed passage of information via the Internet without data loss;

2) Prevention of accidental or unauthorized intentional distortion or change of information during passage;

3) Retransmission if it is received in an incorrect form;

4) Providing methods for splitting long messages into smaller sections for transmitting them and then combining them into a single whole;

5) Providing the possibility of extended communication between two subscribers simultaneously with other subscribers.

IP includes:

1) Methods for uniquely identifying each PC on the Internet so that users can always determine where this or that information came from;

2) Methods for determining the availability of received information;

3) A system that divides information into small portions that could move without interference through any Internet switches.

Each host computer has two addresses:

1) PC friendly digital IP address;

2) User-friendly domain DNS address(Domain name system).

An IP address consists of 4 numbers separated by dots. Each number is 1 byte long, i.e. takes a value from 1 to 255.

123 refers to the higher-level network, 89 directly to the corresponding host PC. The first two numbers are the network address, and the last two numbers are the address of the host PC within that network.

The Domain Name System assigns alphabetic names to PCs, domain names, which are a symbolic form of recording the address of a network PC. For example, to find out the conditions for connecting to NTV+ satellite television, you can try to contact the server www/ntv/ru (ru at the end of the name indicates that the company’s server belongs to the Russian sector of the Internet).

Translation of domain names into related ones IP addresses carried out by DNS domain name service servers.

The Domain Name System is a method of assigning names by assigning responsibility for subsets of names to different groups of users. Each level in this system is called a domain. Domains are separated from one another by dots. In the name m.b. any number of domains, but five is rare. Each subsequent domain (when viewed from left to right) is larger than the previous one.

Initially, there were six top-level organizational domains: commercial organizations - som, educational institutions - edu, government agencies - gov, military institutions - mil, other organizations - org, network resources - net.

In order for foreign countries to control the names of the systems located in them, a two-letter domain was created.

Internet is a World Wide Web where information is stored on servers. Servers have their own addresses and are controlled by specialized programs. They allow you to send mail and files, search databases, etc. Information is exchanged between network servers via high-speed communication channels. Individual users' access to Internet information resources is usually carried out via a telephone network through a provider or corporate network. The provider is an organization that has a modem pool for connecting to clients and accessing the World Wide Web. Note that corporate networks built on the principles of the Internet are called Intranet Internet architecture Let's consider a simplified scheme for building the Internet. Figure 1 shows the network architecture. Dedicated telephone lines, fiber optic and satellite communication channels are used as a high-speed data transmission line. To connect to the Internet, any organization uses a special computer called a gateway. It installs software that processes all messages passing through the gateway. Each gateway has its own IP address. If a message arrives addressed to the local network to which the gateway is connected, it is transmitted to this local network. If the message is intended for another network, then it is forwarded to the next gateway. Each gateway has information about all other gateways and networks. When a message is sent from a local network through a gateway to the Internet, then

Fig.1. Internet architecture

In this case, the “fastest” path is chosen. Gateways exchange information about routing and network status with each other using a special gateway protocol. Some companies may act as a provider. Provider has its own gateway to the Internet and allows other companies and individual users to connect to the Internet through this gateway. In addition to information about message routing, the gateway needs information about the parameters of subnets connected to a larger network in order to adjust message transmission routes in the event of failures in individual parts of the network. Gateways are of two types: internal and external. Internal are called gateways located in a small subnet and providing communication with a larger corporate network. Such gateways communicate with each other using the internal gateway protocol IGP (Internal Gateway Protocol). External gateways used in large networks like the Internet, their settings are constantly changing due to changes in small subnets. Communication between external gateways is carried out via the external gateway protocol EGP (Exterior Gateway Protocol).

Connecting a user to the Internet can be done in different ways, differing in cost, convenience and scope of services provided. These methods are:

electronic mail (E-mail);

teleconferencing (UseNet);

remote terminal emulation system (TelNet);

search and transfer binary files (FTP);

search and transfer text files using the menu system (Gopher);

search and transfer of documents using hypertext links (WWW, or World Wide Web).

The creation and development of these methods are connected historically. Each of them is characterized by its own capabilities and differences in the organization of information exchange protocols. In general, a protocol is understood as a set of instructions that regulate the operation of interconnected systems or objects on a network. Electronic mail (E-mail)- the simplest and affordable way access to Internet networks. It allows you to send any type of files (including texts, images, audio inserts) to email addresses anywhere in the world in a short period of time at any time of the day. To send a message, you only need to know the recipient's email address. Email works based on the sequential transmission of information over a network from one mail server to another until the message reaches the recipient. The advantages of e-mail include high efficiency and low cost. The disadvantage of e-mail is the limited volume of files sent. UseNet designed as a text information exchange system. It allows all Internet users to participate in group discussions, called newsgroups, in which all sorts of problems are discussed. There are now more than 10 thousand teleconferences in the world. Information sent in teleconferences becomes available to any Network client who accesses this teleconference. Nowadays, teleconferencing allows you to transfer any type of file, including text, image and audio files. To work with teleconferences, the tools most often used are programs for viewing and editing Web documents. TelNet is a protocol that allows you to use the resources of a remote computer. In other words, it is a protocol for remote terminal access on a network. In this case, we are talking about transmitting commands from a local computer to a remote computer on the Network. FTP is a Network protocol for working with any type of file: text and binary, which is an example of a system with a client-server architecture. An FTP server is installed on a remote computer in order to provide users with the ability to view file system and copy the required files. To implement communication via the FTP protocol, a program called an FTP server must be running on the remote computer system. The advantage of this protocol is the ability to transfer files of any type - texts, images, executable programs. A disadvantage of the FTP protocol is the need to know the location of the information being sought. Protocol Gopher and the software that implements it provide users with the opportunity to work with information resources without knowing their location in advance. To get started using this protocol, it is enough to know the address of one Gopher server. In the future, the work consists of selecting commands presented in the form of simple and understandable menus. In this case, the menu items of one server can contain links to the menus of other servers, which makes it easier to find the required information on the Internet. When working with the Gopher system, the client program does not maintain a constant connection with the Gopher server, so network resources are spent more economically. WWW (World Web) is the most modern means of organizing network resources. It is built on the basis of hypertext presentation of information. Hypertext- this is text containing links to other parts of this document, to other documents, to objects of non-text nature (sound, image, video), as well as a system that allows you to read such text, track links, display pictures and play sound and video inserts. Hypertext with non-text components (sound, video) is called hypermedia. The ultimate goal of the WWW is to unite all network resources (files, texts, databases, server programs) into a single worldwide hypertext. The operation of the Internet is based on the use of a family of communication protocols - Transmission Control Protocol / Internet Protocol - TCP/IP), which is used for data transmission on the global network and in many local networks. TCP/IP is a family of protocols. It includes protocols that can be divided according to purpose into the following groups:

transport protocols used to control data transfer between two computers;

routing protocols that handle data addressing and determine the shortest available paths to the destination;

network address support protocols designed to identify a computer by its unique number or name;

application protocols that provide access to various network services;

gateway protocols that help transmit routing messages and network status information over a network, and process data for local networks;

other protocols that do not fall into these categories, but provide the client with the convenience of working on the network.

The TCP/IP architecture is built on the basis of the reference model, but in it the first three layers of the OSI model are combined into one (Fig. 2).

ModelOSI
Application layer	Application layer
Presentation layer
Network User Interface Layer
Transport layer	Transport layer
Network layer	Internet
Data Link Layer	Network interface
Physical layer	Physical layer

Fig.2. Reference Model Layers and TCP/IP Protocols

Any document or message is sent to the network from an application program (application layer). Then, through a modem and a telephone line (transport layer), the message reaches an Internet node and then, using network programs(network interface) is transmitted to the communication line of the global network nodes (physical layer). Programs at each level process the message or transmitted document in their own way, without knowing anything about its content. Network addresses On the Internet, each computer is assigned its own unique network address - an IP address, which is 32 bits long and consists of 4 parts of 8 bits. Each part can take values ​​from 0 to 255 and is separated from other parts by a dot. For example, 194.105.195.17 and 147.115.3.27 represent two IP addresses. A network address has two parts: the network address and the host address on that network. Under host refers to a computer connected to a network and providing various network services. Thanks to this IP address structure, computers on different networks can have the same addresses. To ensure maximum flexibility, IP addresses are divided into classes A, B, C and are allocated depending on the number of local networks and computers in them. These three classes of IP addresses determine the size of an organization's local network. Depending on the class, the full 32-bit address is broken down into 8-bit components in different ways. In this case, the first one to three bits at the beginning of the IP address identify the corresponding class. The structure of IP addresses is shown in Fig. 3.

Fig.3. IP address structure

By the first number of the IP address, you can determine the type of class to which the organization belongs: Class A addresses are numbers from 0 to 127. Class B addresses are numbers from 128 to 191. Class C addresses are numbers from 192 to 223. Class A network address allows you to identify more than 16 million computers in an organization’s local network, but there can be no more than 128 local networks of this class. A class B network address allows you to allocate a larger number of local networks, but with a smaller number of computers on the network itself. Finally, Class C networks can have a maximum of 254 computers, but there can be over 2 million such networks. When sending a message on the Internet, the IP address is used to indicate the sender and recipient. The client does not need to remember network addresses because the network uses domain names, which are converted by the domain name system to IP addresses. Domain addressing Internet addresses are built using the domain name system (DNS). This means that the user's address consists of two parts: the user ID and the domain name, separated by the @ symbol

<идентификатор пользователя>@<название домена>

The user ID and domain name can consist of segments separated by a dot. The address may use Latin letters, numbers and some other symbols. For example:

Ivan. [email protected]

In the example, the user ID consists of two segments, and the domain name consists of four. Typically, domain segments or subdomains form a hierarchical structure: the first subdomain on the left is usually the name of the computer to which that address is assigned, the next one refers to the name of the organization where that computer is located, and the one on the far right (the subdomain top level) is an abbreviation for country. The address given means that it belongs to Ivan Kirillov, an employee of the Faculty of Law of the St. Petersburg University of Russia, who has a computer named mycomputer. User IDs can be anything: full first and last name, initials, last name with initials, nicknames, and names of organizations or departments. In this case, on one computer there can be an arbitrary (limited by the permissible number of IP addresses) number of registered users with their own addresses, or a user can have several addresses on the domain (one, for example, for personal correspondence, and the other for official correspondence). Moreover, you can have several addresses on different computers. The top-level subdomain, indicating the country, usually consists of two letters: ru-Russia, su- territory of the republics of the former Union, ca- Canada, uk- Great Britain, ua- Ukraine, de- Germany, etc. The USA traditionally uses a different system. The top-level subdomain consists of three letters and indicates that the owner of the address belongs to one of the following classes: com - commercial organizations; edu - educational and scientific organizations; gov - government agencies; mil - military organizations; net - network administration; org - other organizations. In Russia, a second-level subdomain usually designates the city or geographic region where this address is located, for example: msk - Moscow; spb - St. Petersburg; nsk - Novosibirsk; altai - Altai Territory. Note that in the UK, address subdomains arranged in reverse order.

Web document viewers

To work in WWW on your computer you must have special program - browser(browser). A browser is an application program that interacts with the WWW and allows you to receive various documents from the network, view and edit their contents. Browsers provide the ability to work with documents containing text and multimedia information. In addition, they support all the previously discussed methods and protocols for accessing the Internet. In WWW documents, as a rule, contain hypertext (text with hyperlinks). Unlike ordinary text, documents on the Internet contain commands that define their structure, including links to other documents. This allows the browser to format the document for display on the screen in accordance with the capabilities of a particular computer. Since the Internet uses heterogeneous hardware and software, a universal hypertext markup language, HTML (HyperText Markup Language), was adopted to develop Web pages. HTML includes a set of commands used to describe the structure of a document. Using HTML, a document is divided into appropriate logical components: paragraphs, headings, lists, etc. The specific formatting attributes of the document (body text and highlighted components) when viewing it are determined by the browser used. The most common browsers are:

Mosaic for Windows;

Cello program;

Linx program;

• MicroSoft Internet Explorer(MSIE);

  Netscape Communicator.

Let's briefly consider their purpose and main capabilities. The main focus will be on MSIE, as one of the most popular browsers. His latest version 4.0 is distributed on the Internet by Microsoft free of charge and is included in Windows 98. Mosaic For Windows- one of the first viewing programs. It has a very simple graphical user interface and allows you to display formatted Web documents on the screen. Its disadvantage is the need to install additional software for working with graphic files, audio and video images, which is not included as standard in the browser. The program Cello was developed as an alternative to Mosaic. Directly provides access to HTTP, Gopher, FTP servers, UseNet teleconferences, and also supports working with Telnet when using external client programs. The program has a very simple interface, which allows you to quickly master working with it. The inconvenience of working with the browser is the small number of buttons on the control panel, so you constantly have to work with drop-down menus. The program Linx refers to browsers with a text interface. Hypertext links are highlighted on the screen with a different color or an inversion of the background and text colors. The advantage of this browser is the ability to quickly find text information on the WWW using hypertext links. Pages you have viewed can be marked using bookmarks, which can be created while working in the browser. Browser EINet WinWeb differs for the better in the small amount of main memory occupied during operation, good support for interactive forms, stable and reliable operation. The navigation mechanism is implemented simply and conveniently for the user. There is a built-in tool for searching documents using keywords. Browser settings allow you to select the fonts and colors used when displaying documents and highlighting hyperlinks. Browser Internet Works allows you to work not only with WWW, but also with FTP and Gopher servers. The documents the user works with can be presented at three levels. In this case, the transition from page to page can occur both within one level and between them, using the toolbar buttons and the ability to work in multi-window mode. Viewing a text document can occur while simultaneously downloading multimedia files in the background. It is possible to customize the interface by the user. The generally recognized leaders among programs for viewing and editing Web documents - the Netscape Communicator and MicroSoft Internet Explorer browsers are the most convenient and multifunctional. They allow you to display on the screen any documents created in any operating environment and on any computer with a configuration that allows for network operation.

Microsoft Internet Explorer 4.0

According to various experts, this browser is almost superior in ease of use and functionality to Netscape Communicator. It consists of the following components:

MSIE Browser;

• desktop update component;

  Outlook Express;

  Microsoft NetMeeting;

• FrontPage Express;

  task Manager.

MSIE Browser allows you to view Web pages from Windows Explorer, from My Computer, and even from the Control Panel. In this case, the page can be located on the Internet, on a corporate network, or on a computer’s hard drive. The Windows Explorer panel takes the form of a Web page, which greatly simplifies the work and speeds up the process of finding the necessary nodes. The browser allows you to set different levels of protection, such as prohibiting the display of unwanted information, for example, related to violence. You can protect your computer from potentially dangerous files and programs by setting different levels of protection for different Internet zones. When making purchases online, you can protect your credit card and delivery address using the Microsoft Wallet electronic wallet included with the Explorer. The most interesting information from the network can be sent directly to your desktop. To do this, you only need to subscribe to necessary channels. The channel is displayed as a shortcut on the desktop and is regularly updated by the information provider. For example, every morning you can receive the latest sports news. The user himself can create any one he is interested in. channel.Desktop can be designed as a Web page with direct display of information that will be updated automatically. For example, you can place a news ticker from the Internet on your desktop. To open folders with files and launch programs, just one click with the left mouse button is enough. To select an element, you just need to point at it with the mouse. Outlook Express is an Internet Explorer mail and news program that allows you to exchange email messages, as well as read and send group news messages and work with newsgroups. You can easily switch between mail folders, news servers, and news groups. News is usually downloaded to a computer for later viewing offline, without wasting time connecting to the Internet. Microsoft NetMeeting allows you to hold conferences on the Web or local network. This can use a network or modem. During a conference, you can talk with your interlocutor via the Internet, with a video image (if you have a video camera connected to your computer), and also work in a common application. Microsoft Chat used for online negotiations in a special conversation room. This uses a comic book graphic format or a regular text format. The user is given the opportunity to select a drawn character who will represent him during negotiations with several People at once. You can talk to some of them secretly from the rest. FrontPage Express serves to create, edit and publish your own Web pages. It includes a set of templates with which you can create Web pages of any complexity with any number of links to other information sources. Task Manager serves for planning and executing some standard procedures. It starts with Windows and runs in the background, running specified programs at specific times.

Lecture

Us – USA;

Ru – Russia;

ua – Ukraine, etc.

by type of organization:

com – commercial organizations;

edu – educational institutions;

net – Internet service centers;

int – international organizations;

org – other organizations, etc.

Owner of the zone.by – Open Contact (www.ok.open.by)

Provider is an organization licensed to provide access to Internet services.

Providers RB: Open contact (www.ok.open.by)

Belpak (www.beltelecom.by), etc.

4. Search for information on the Internet.

Searching for information on the Internet can be done using:

· Website URLs;

· links on open pages of websites;

· information retrieval systems (IRS).

Search relevance is the degree to which search results match search queries.

Types of IPS:

· search engines (directories and search engines);

· metasearch engines;

· accelerated search programs.

In the IRS, an index database is created and maintained up to date, containing links to informational resources Internet. All user search requests are translated into formal queries to the index database. Search results are displayed as a list of annotations with links to relevant Web pages.

The search engine has a special program (robot indexer) that scans all Internet sites and forms an index database. The search is performed using a query consisting of several keywords and, possibly, elements of the query language (+, -, ?, &, NOT, OR, etc.) The search can be simple or advanced, clarifying the search parameters and displaying results.

The most common search engines:

Rambler – www.rambler.ru

Yandex – www.yandex.ru

Google – www.google.com

AltaVista – www.altavista.com

All.by – www.all.by

The catalog is a search system with annotations and links to Web resources divided by topic. The search is performed through a sequence of refined topics. The index database is created manually by the directory administrator.

Most modern information retrieval systems are both catalogs and search engines.

The most common directories:

Yahoo – www.yahoo.com

List – www.list.ru

Constellation Internet – www.stars.ru

Metasearch engines do not have their own index database, but send user queries to several search engines and combine the results obtained. For example, www.search.com.

Internet network

1. History of the creation of the Internet

After the Soviet Union launched the artificial Earth satellite in 1957, the US Department of Defense decided that in case of war, America needed a reliable information transmission system. The US Advanced Research Projects Agency (ARPA) proposed developing a computer network for this purpose. The development of such a network was entrusted to the University of California at Los Angeles, the Stanford Research Center, the University of Utah and the University of California at Santa Barbara. The computer network was called ARPANET (Advanced Research Projects Agency Network), and in 1969, as part of the project, the network united four specified scientific institutions, all work was funded by the US Department of Defense. Then the ARPANET network began to actively grow and develop, and scientists from different fields of science began to use it.

The first ARPANET server was installed on September 1, 1969 at the University of California, Los Angeles. The Honeywell 516 computer had 12 KB of RAM.

By 1971, the first program for sending email over the network was developed, and the program immediately became very popular. In 1973, the first foreign organizations from Great Britain and Norway were connected to the network via a transatlantic telephone cable, and the network became international.

In the 1970s, the network was primarily used for sending email, and the first mailing lists, news groups, and bulletin boards emerged. However, at that time the network could not yet easily interact with other networks built on other technical standards.

By the end of the 1970s, data transfer protocols began to develop rapidly, which were standardized in 1982-83. Active role in development and standardization network protocols played by Jon Postel. On January 1, 1983, the ARPANET switched from the NCP protocol to TCP/IP, which is still successfully used to connect (or, as they also say, “layer”) networks. It was in 1983 that the term “Internet” was assigned to the ARPANET network.

In 1984, the Domain Name System (DNS) was developed.

In 1984, the ARPANET network had a serious rival, the US National Science Foundation (NSF) founded an extensive inter-university network NSFNet (abbreviated from the English National Science Foundation Network), which was made up of smaller networks (including the then famous Usenet and Bitnet networks) and had much more throughput than ARPANET. Over the course of a year, about 10 thousand computers connected to this network, and the title “Internet” began to smoothly pass to NSFNet.

In 1988, the Internet Relay Chat (IRC) protocol was invented, making real-time communication (chat) possible on the Internet.

In 1989 in Europe, within the walls of the European Council for Nuclear Research (French: Conseil Européen pour la Recherche Nucléaire, CERN), the concept of World Wide Web. It was proposed by the famous British scientist Tim Berners-Lee, who developed the HTTP protocol within two years, HTML language and URL identifiers.

In 1990, the ARPANET network ceased to exist, completely losing competition to NSFNet. In the same year, the first Internet connection was recorded via telephone line(so-called “dial-up” in English: Dialup access).

In 1991, the World Wide Web became available to the public on the Internet, and in 1993, the famous NCSA Mosaic web browser appeared. The World Wide Web was gaining popularity.

Currently, the Internet is accessible not only through computer networks, but also through communication satellites, radio signals, cable television, telephone, cellular communication, special fiber optic lines and electrical wires. The World Wide Web has become an integral part of life in developed and developing countries.

Internet is a collection of interconnected computer networks, which use uniform agreed rules for data exchange between computers.

The Internet is:

Ø fast and convenient international means of communication;

Ø public mass media;

Ø a means of mass ordering goods and services;

Ø means of provision remote access to sources of information;

Ø world library;

Ø email;

Ø electronic bulletin boards and teleconferences;

Ø a means of entertainment.

The Internet (as a whole) does not have any owner, although each network included in it is owned by a company, non-profit or government organization. There is also no special governing body that would control the entire operation of the Internet. Regional networks of various countries are financed and managed by their owners in their interests and in accordance with the laws of a particular state.

3. TCP/IP protocols

The Internet differs from other networks in its protocols, primarily the TCP/IP protocols.

Protocol – this is a set of rules that determine the nature of user interaction and the sequence of actions they take when exchanging information.

The term TCP/IP means everything related to communication protocols between computers on a network.

The TCP/IP protocol gets its name from two types of communication protocols:

Ø Transmission Control Protocol (TCP);

Ø Internet Protocol (IP).

Protocol IP is responsible for finding a route (or routes) on the Internet from one computer to another through many intermediate networks, gateways and routers and transmitting blocks of data along these routes.

Protocol TCP ensures reliable delivery, error-free and correct order of reception of transmitted data.

The Internet uses a large number of other protocols, but this network is often called a TCP/IP network, since these two protocols are the most important.

Target: become familiar with the structure and basic operating principles worldwide network Internet, with basic Internet protocols and addressing system.

Architecture and operating principles of the Internet

Global networks, reaching millions of people, have completely changed the process of dissemination and perception of information.

Wide Area Network (WAN)– these are networks designed to connect individual computers and local networks located at a considerable distance (hundreds and thousands of kilometers) from each other. Global networks connect users located around the world using a wide variety of communication channels.

Modern Internet- a very complex and high-tech system that allows the user to communicate with people located anywhere in the world, quickly and comfortably find any necessary information, and publish for public information the data that he would like to communicate to the whole world.

In reality, the Internet is not just a network, it is a structure that unites ordinary networks. The Internet is a “network of networks.”

To describe today's Internet, it is useful to use a strict definition.

In his book « TheMatrix:ComputerNetworksandConferencingSystemsWorldwide » John Quarterman describes the Internet as “a metanetwork consisting of many networks that operate according to the TCP/IP family of protocols, connected through gateways and using a single address space and name space”.

There is no single point of subscription or registration on the Internet; instead, you contact a service provider who gives you access to the network through a local computer. The consequences of such decentralization in terms of the availability of network resources are also quite significant. The data transmission environment on the Internet cannot be considered only as a web of wires or fiber optic lines. Digitized data is sent via routers , which connect networks and, using complex algorithms, select the best routes for information flows (Fig. 1).

Unlike local networks, which have their own high-speed information transmission channels, global (as well as regional and, as a rule, corporate ) the network includes a communication subnetwork (otherwise: a territorial communication network, an information transmission system), to which local networks, individual components and terminals (means for entering and displaying information) are connected (Fig. 2).

The communication subnetwork consists of information transmission channels and communication nodes, which are designed to transmit data over the network, select the optimal route for transmitting information, switch packets and implement a number of other functions using a computer (one or more) and the corresponding software available in the communication node. The computers on which client users work are called workstations , and computers that are sources of network resources provided to users are called servers . This network structure is called nodal .

Fig.1 Scheme of interaction on the Internet

Internet is a global information system that:

· logically interconnected by the space of globally unique addresses based on the Internet Protocol (IP);

· capable of supporting communications using the Transmission Control Protocol family - TCP/IP or its subsequent extensions/successors and/or other IP-compatible protocols;

· provides, uses, or makes available, on a public or private basis, high-level services built on top of the communications and other related infrastructure described herein.

Internet infrastructure(Fig.2):

1.backbone level (system of connected high-speed telecommunication servers).

2.level of networks and access points (large telecommunications networks) connected to the backbone.

3.level of regional and other networks.

4.ISP – Internet providers.

5.users.

To technical resources on the Internet include computer nodes, routers, gateways, communication channels, etc.

Fig.2 Internet infrastructure

The network architecture is based on multi-level message transmission principle . The message is generated usingthe highest level of the model ISO/OSI .. Then (when transmitting) it is afterThe message consistently passes through all levels of the system to the lowest level, where it is transmitted via a communication channel to the recipient. As each one passesfrom the levels of the system the message is transformed, divided into relatively short parts that are equipped with additionalwith headers that provide similar levels of informationnor on the destination node. At this node, the message passes from the lower level to the upper level, stripping itself of headers. As a result, the recipient receives the message in its original form.

In territorial networks data exchange management realizedis based on the top-level protocols of the model ISO/OSI . Regardless internal design of each specific top protocollevel, they are characterized by the presence of common functions: initialization of communication, transmission and reception of data, completion of exchange. Every protothe count has the means to identify any workstation on the networkby name, network address, or both. Activization of information exchange between interacting nodesis found after the destination node has been identified by the initiating nodedata exchange. The originating station installs one of the Methods for organizing data exchange: datagram method or method communication sessions. The protocol provides a means to receive/transmitchi messages by addressee and source. In this case, usually overlayingThere are restrictions on the length of messages.

TCP/IP- internetworking technology

The most common exchange control protocoldata is the TCP/IP protocol. The main difference between the network Internet from other networks lies precisely in its TCP/IP protocols, coveringcontaining a whole family of protocols for interaction between computersterami network. TCP/IP is an internetworking technology Internet technology. Therefore r a global network that connects manyvariety of networks with technologyTCP/IP, called Internet.

TCP/IP protocol is a family of software-implementedhigher-level protocols that do not work with hardware devicesjerking. Technically, the TCP/IP protocol consists of two parts - IP and TCP.

Protocol IP ( Internet Protocol - internetwork protocol) is the main protocol of the family, it implements the distribution of information formations in IP -network and is executed at the third (network) level of the mode whether ISO/OSI. IP protocol provides datagram delivery to the packageComrade, its main task is packet routing. He is not responsible for the reliability of information delivery, for its integrity, for the preservationchanging the order of the packet flow. Networks that use the protocol IP, called IP -networks. They work mainly analogue channels (i.e., to connect a computer to the network you need IP-mo dem) and are packet switched networks. The package is called hereyes datagram.

High level protocol TCP ( Transmission Control Protocol- transmission control protocol) works at the transport layer andpartially - at the session level. This is a protocol with the establishment of lological connection between sender and recipient. He is promisedprints a session connection between two nodes with guaranteed delivery of information, monitors the integrity of the transmission information received, preserves the order of the packet flow.

For computers, the TCP/IP protocol is the same as the rulestalk for people. It is accepted as an official standard on the web Internet , i.e. network technology TCP/IP has become the de facto technologygy of the World Wide Web.

A key part of the protocol is a packet routing scheme based on unique network addresses. Internet. Each work tea station, part of a local or global network, hasThere is a unique address that includes two parts identifyingnetwork address and station address within the network. This scheme allows give messages both within this network and to external networks.

ADDRESSING ON THE INTERNET

Basic Internet protocols

The operation of the Internet is based on the use of families of communication protocols TCP/IP (TransmissionControlProtocol/ InternetProtocol). TCP/IP is used for data transmission both on the Internet and on many local networks.

The name TCP/IP defines a family of network data transfer protocols. Protocol is a set of rules that all companies must adhere to to ensure the compatibility of the hardware and software they produce. These rules ensure that the hardware and software produced are compatible. In addition, TCP/IP is a guarantee that your Personal Computer will be able to communicate via the Internet with any computer in the world that also works with TCP/IP. As long as certain standards are met for the operation of the entire system, it does not matter who the software or hardware manufacturer is. The open systems ideology involves the use of standard hardware and software. TCP/IP is an open protocol and all specific information is published and can be freely used.

The various services included in TCP/IP and the functions of this protocol family can be classified according to the type of tasks they perform. We will only mention the main protocols, since their total number amounts to more than a dozen:

· transport protocols- manage data transfer between two machines :

· TCP/ IP(Transmission Control Protocol),

· UDP(User Datagram Protocol);

· routing protocols- process data addressing, ensure the actual transfer of data and determine the best path for the packet to travel :

· IP(Internet Protocol),

· ICMP(Internet Control Message Protocol),

· R.I.P.(Routing Information Protocol)

· and others;

· network address support protocols- process data addressing, provide machine identification with a unique number and name :

· DNS(Domain Name System),

· ARP(Address Resolution Protocol)

· and others;

· application service protocols are programs that a user (or computer) uses to access various services :

· FTP(File Transfer Protocol),

· TELNET,

· HTTP(HyperText Transfer Protocol)

· NNTP(NetNewsTransfer Protocol)

·and others

This includes transferring files between computers, remote terminal access to the system, transmission of hypermedia information, etc.;

· gateway protocols help transmit routing messages and network status information over the network, as well as process data for local networks :

· E.G.P.(Exterior Gateway Protocol),

· GGP(Gateway-to-Gateway Protocol),

· IGP(Interior Gateway Protocol);

· other protocols– used to transmit email messages, when working with directories and files on a remote computer, and so on :

· SMTP(Simple Mail Transfer Protocol),

· NFS(Network File System).

IP-addressing

Now let's take a closer look at the concept of IP address.

Every computer on the Internet (including any PC when it establishes a session connection with an ISP over a telephone line) has a unique address called IP-address.

An IP address is 32 bits long and consists of four 8-bit parts, named according to network terminology octets (octets) . This means that each part of the IP address can have a value between 0 and 255. The four parts are combined into a notation in which each eight-bit value is separated by a period. When we talk about a network address, we usually mean an IP address.

If all 32 bits of an IP address were used, there would be over four billion possible addresses - more than enough for the future expansion of the Internet. However, some bit combinations are reserved for special purposes, which reduces the number of potential addresses. In addition, the 8-bit quads are grouped in special ways depending on the type of network, so that the actual number of addresses is even smaller.

With the concept IP addresses are a closely related concept hosta (host) . Some simply equate the concept of a host with the concept of a computer connected to the Internet. In principle, this is true, but in general under host refers to any device that uses the TCP/IP protocol to communicate with other equipment. That is, in addition to computers, these can be special network devices - routers, hubs and others. These devices also have their own unique I P addresses, just like the computers of users’ network nodes.

Any IP-the address consists of two parts: network addresses(network identifier, Network ID) and host addresses(host identifier, Host ID) on this network. Thanks to this structure, the IP addresses of computers on different networks can have the same numbers. But since the network addresses are different, these computers are uniquely identified and cannot be confused with each other.

IP addresses are allocated depending on the size of the organization and the type of its activities. If this is a small organization, then most likely there are few computers (and, therefore, IP addresses) on its network. In contrast, a large corporation may have thousands (or even more) of computers organized into many interconnected local networks. For maximum flexibility IP-addresses are divided into classes: A, B and C. There are also classes D And E, but they are used for specific service purposes.

So, three classes of IP addresses allow them to be distributed depending on the size of the organization's network. Since 32 bits is the legal full size of an IP address, the classes break the four 8-bit parts of the address into a network address and a host address depending on the class.

Class network addressA determined by the first octet of the IP address (counted from left to right). The value of the first octet, which is in the range 1-126, is reserved for giant multinational corporations and the largest providers. Thus, in Class A there may be only 126 large companies in the world, each of which may contain almost 17 million computers.

ClassBuses The first 2 octets as the network address, the value of the first octet can range from 128-191. Each Class B network can have about 65 thousand computers, and the largest universities and other large organizations have such networks.

Respectively, in classC The first three octets are already allocated for the network address, and the value of the first octet can be in the range 192-223. These are the most common networks, their number can exceed more than two million, and the number of computers (hosts) in each network can be up to 254. It should be noted that “gaps” in the permissible values ​​of the first octet between classes of networks appear due to the fact that one or several bits are reserved at the beginning of the IP address to identify the class.

If any An IP address is symbolically designated as a set of octets w .x .y .z, then the structure for networks of various classes can be presented in Table 1.

Whenever a message is sent to any host on the Internet, the IP address is used to indicate the sender and recipient addresses. Of course, users do not have to remember all the IP addresses themselves, since there is a special TCP/IP service for this, called the Domain Name System.

Table 1. Structure of IP addresses in networks of various classes

Network class	First octet value (W)	Network number octets	Host number octets	Number of possible networks	Number of hosts in such networks
	1-126		x.y.z	128(2 7)	16777214(2 24)
	128-191	w.x	y.z	16384(2 14)	65536(2 16)
	192-223	w.x.y		2097151(2 21)	254(2 8)

The concept of a subnet mask

To separate the network ID from the host ID, a special 32-bit number called a subnet mask is used. Purely outwardly, a subnet mask is exactly the same set of four octets, separated by dots, like any IP address. Table 2 shows the default subnet mask values ​​for class A, B, C networks.

Table 2. Subnet mask value (default)

Network class	Mask value in bits (binary representation)	Mask value in decimal form
	11111111 00000000 00000000 00000000	255.0.0.0
	11111111 11111111 00000000 00000000	255.255.0,0
	11111111 11111111 1111111100000000	255,255.255.0

The mask is also used to logically divide large IP networks into a number of smaller subnets. Let's imagine, for example, that at the Siberian Federal University, which has a class B network, there are 10 faculties and 200 computers (hosts) are installed in each of them. By using a subnet mask of 255.255.0.0, this network can be divided into 254 separate subnets with up to 254 hosts each.

The default subnet mask values ​​are not the only possible ones. For example, a system administrator on a particular IP network might use a different subnet mask value to highlight just some of the bits in the host ID octet.

How to registerIP-the network of your organization?

In fact, end users are not involved in this task, which falls on the shoulders of the system administrator of a given organization. In turn, he is assisted in this by Internet providers, usually taking upon themselves all registration procedures in the relevant international organization called InterNIC (NetworkInformationCenter). For example, Siberian Federal University wants to receive an Internet email address containing the string sfu -kras .ru. This identifier, which includes the company name, allows the sender of the email to identify the recipient's company.

To obtain one of these unique identifiers, called a domain name, a company or ISP sends a request to the authority that controls Internet connections - InterNIC. If InterNIC (or the body authorized by it for such registration in a given country) approves the company name, then it is added to the Internet database. Domain names must be unique to prevent errors. The concept of a domain and its role in addressing messages sent over the Internet will be discussed below. Additional information You can learn about the work of InterNIC by visiting the Internet page http://rs.internic.ru.

DOMAIN NAME SYSTEM

Domain names

In addition to IP addresses, the so-called Domain host name . Just like an IP address, it is a name is unique for each computer (host) connected to the Internet - only here words are used instead of digital address values.

In this case, the concept domain means a collection of Internet hosts united according to some characteristic (for example, by territorial, when we are talking about the domain of the state).

Of course, the use of a domain host name was introduced only to make it easier for users to remember the names of the computers they need. The computers themselves, for obvious reasons, do not need such a service and make do with IP addresses. But just imagine that instead of such sonorous names as, www. microsoft. com or www. ibm. com you would have to remember the sets of numbers - 207.46.19.190 or 129.42.60.216 respectively.

If we talk about the rules for composing domain names, then there are no such strict restrictions on the number of components of the name and their meanings as in the case of IP addresses. For example, if in KhTI - Branch of Siberian Federal University there is a host with the name khti, included in the domain of the Republic of Khakassia khakassia, and that, in turn, is part of the Russian domain ru, then the domain name of such a computer will be khti. khakassia. ru. In general, the number of components of a domain name can be different and contain one or more parts, for example, rage. mp3. apple. sda. org or www. ru .

Most often, a company’s domain name consists of three components, the first part is the host name, the second is the company’s domain name, and the last is the country’s domain name or the name of one of seven special domains indicating the affiliation of the host with an organization of a certain activity profile (see Table 1 ). So, if your company is called "KomLinc", then most often the company's Web server will be named www.komlinc.ru (if it is a Russian company), or, for example, www.komlinc.com, if you asked the provider to register you mainly international domain of commercial organizations.

The last part of the domain name is called the top-level domain identifier (for example, . ru or . com). There are seven top-level domains established by InterNIC.

Table1. International top level domains

domain name	Domain host ownership
ARPA	Great-great... grandmother of the Internet, ARPANet network (obsolete)
COM	Commercial organizations (firms, companies, banks, etc.)
GOV	Government agencies and organizations
EDU	Educational institutions
MIL	Military institutions
NET	"Network" organizations that manage the Internet or are part of its structure
ORG	Organizations that do not belong to any of the listed categories

Historically, these seven default top-level domains denote the fact that a host (belonging to them) is geographically located in the United States. Therefore, the international committee InterNIC, along with the above top-level domains, allows the use of domains (special combinations of characters) to identify other countries in which the organization that owns this host is located.

So, top level domains are divided into organizational(see table 1) and territorial. There are two-letter designations for all countries of the world: . ru- for Russia (the domain is still in use . su, uniting hosts on the territory of the republics of the former USSR), .sa- for Canada, . uk- for Great Britain, etc. They are usually used in place of one of the seven identifiers listed in Table 1 above.

Territorial top level domains:

. ru (Russia) - Russia;

Su (Soviet Union ) - countries of the former USSR, now a number of CIS countries;

UK (United Kingdom ) - Great Britain;

Ua (Ukraine) - Ukraine;

Bg (Bulgaria) - Bulgaria;

Hu (Hungary) - Hungary;

De (Dutchland ) - Germany, etc.

C full list All domain names of countries can be found on various servers on the Internet.

Not all companies outside the US have country IDs. To some extent, whether you use a country identifier or one of the seven US identifiers depends on when the company's domain name was registered. Thus, companies that connected to the Internet quite a long time ago (when the number of registered organizations was relatively small) were given a three-letter identifier. Some corporations operating outside the US but registering a domain name through a US company choose whether to use the host country identifier. Today in Russia you can get a domain identifier . com, for which you should discuss this issue with your Internet provider.

HowworkserversDNS

Now let's talk about how domain names are converted into computer-readable IP addresses.

Is doing this DomainNameSystem(DNS, Domain Name System) a service provided by TCP/IP that helps in addressing messages. It is thanks to the work of DNS that you can not remember the IP address, but use a much simpler domain address. The DNS system translates a computer's symbolic domain name into an IP address by finding an entry in a distributed database (stored on thousands of computers) that matches it domain name. It is also worth noting that DNS servers in Russian-language computer literature they are often called "name servers".

Root zone name servers

Although there are thousands of name servers in the world, at the top of the entire DNS system are nine servers called root zone servers ( root zone servers ) . Root zone servers are named a. root_ server. net, b. root_ server. net and so on until i. root_ server. net. The first one is a. root_ server. net- acts as the primary Internet name server, controlled from the InterNIC information center, which registers all domains included in several top-level domains. The remaining name servers are secondary to it, but they all store copies of the same files. Thanks to this, any of the root zone servers can replace and back up the others.

These computers contain information about the host computers of the name servers serving seven top-level domains: .com, .edu, .mil, .gov, .net, .org and special.arpa (Fig. 1). Any of these nine servers carries the same top-level file as .uk (UK), .de (Germany), .jp (Japan) and so on.

Rice. 1. Hierarchical structure of Internet domain names

The root zone files contain all host names and IP -name server addresses for each subdomain included in the top-level domain. In other words, each root server has information about all top-level domains, and also knows the name of the host computer and IP -the address of at least one name server serving each of the secondary domains included in any top-level domain. For domains of foreign countries, the database stores information on name servers for each country. For example, in a certain domaincompany. comroot zone files for a domain contain nameserver information for any address ending incompany. com.

In addition to the root zone nameservers, there are local name servers , installed in lower level domains. The local name server caches a list of host computers that it has recently searched for. This eliminates the need to constantly access the system DNS with queries about frequently used host computers. Additionally, local name servers are iterative, and the root zone servers are recursive. This means that the local name server will repeat the process of requesting information about other name servers until it receives a response.

Root servers Internet , located at the top of the structure DNS , on the contrary, only provide pointers to the next level domains. Get to the end of the chain and get the required IP -address is the task of the local name server. To solve it, he must go down the hierarchical structure, sequentially asking local servers names are pointers to its lower levels.

Today you won't surprise anyone with the Internet. A huge number of users access this network every day. According to 2015 data, the number of connected users exceeded 3.3 billion. True, not everyone knows what the structure of the Internet is in technical terms. Most people don't really need this. However, the foundations laid down in the principles of operation of the World Wide Web, at least entry level you still need to know.

What is the Internet in a modern interpretation

In general, when we're talking about O modern Internet, quite often the concept of the World Wide Web or Network is used instead, into which computers from all over the world are united.

In general, this is true, but one clarification should be made here. As you know, not a single computer connects directly to the Internet, only through a service provider, to which God knows how many other terminals or mobile devices. It turns out that they are all united into one network. And in this sense, the Internet is called a “network of networks.”

Indeed, the structure of the Internet is based on combining, so to speak, subnets and has a high-tech hierarchy. In addition, accessing a particular resource is impossible to imagine without a router that is able to choose the optimal path for accelerated access to a given resource.

And here's what's interesting. The Internet as such has no owner, and the network itself is rather a virtual space, which affects people more and more every day, sometimes even replacing reality. Whether this is good or bad is not for us to judge. But let’s dwell on the main aspects of the construction and functioning of the World Wide Web.

Structure of the global Internet: history of emergence and development

The Internet was not always the way we know it today. If we delve into history, it should be noted that the first attempts to create a unified information network that could not only transmit data, but also serve in some way as a “translator” of many programming languages ​​for perceiving information were made back in 1962, the very the height of the Cold War between the USA and the USSR. Then a program based on packet switching theory appeared for Leonard Kleinrock, led by Joseph Licklider. The main focus was not only but also its “indestructibility”.

Based on these developments, the first network emerged in 1969, called ARPANet, which became the progenitor of the Internet, or World Wide Web. In 1971, the first program for sending and receiving e-mail was developed, by 1973, when the Euro-Atlantic cable was continued, the network became international, in 1983 it switched to the unified TCP/IP protocol, in 1984 IRC technology appeared, which made it possible to chat . And only by 1989, the idea of ​​​​creating a global web, which is now commonly called the Internet, matured at CERN. Of course, it was far from the model used now, however, some basic principles that include the structure of the Internet have still remained unchanged.

World Wide Web Infrastructure

Now let's see how we managed to combine individual computer terminals and networks based on them into a single whole. The key principle was the use of packet data transmission using routing based on a universal protocol that could be understood by any machine. That is, information is not represented in the form of individual bits, bytes or characters, but is transmitted in the form of a formatted block (packet), which can contain quite long combinations of various sequences.

However, the transfer itself does not happen haphazardly. At the same time, Internet resources have several main levels:

• Backbone (a system of high-speed servers connected to each other).
• Large networks and access points connected to the main backbone.
• Regional networks rank lower.
• Internet service providers (ISPs).
• End users.

The Internet is such that the terminals on which it is stored are called servers, and the user machines (reading or receiving it, as well as sending feedback and streams) are called workstations. The transmission of the information itself, as mentioned above, is carried out on the basis of routers. But this diagram is presented solely for ease of understanding the issue. In reality, everything is much more complicated.

Basic protocols

Now we come to one of the key concepts, without which it is impossible to imagine what the structure of the Internet is. These are universal protocols. Today there are quite a lot of them, but the main one for the Internet is TCP/IP.

In this case, it is necessary to clearly distinguish between the two terms. The Internet Protocol (IP) is one of the means of routing, that is, it is solely responsible for the delivery of data packets, but is in no way responsible for the integrity and security of the transmitted information. The TCP protocol, on the contrary, is a means of providing session communication between the sender and the recipient based on a logical connection between two points with the so-called guaranteed delivery of packets, and absolutely intact.

Today, TCP/IP is the de facto Internet standard, although there are many other protocols, such as UDP (transport), ICMP and RIP (routers), DNS and ARP (network address identification), FTP, HTTP, NNTP and TELNET (application applications). ), IGP, GGP and EGP (gateway), SMTP, POP3 and NFS (mail and file access protocols on remote terminals), etc.

Domain Name System

Separately, it should be noted the universal approach to accessing resources. It is clear that writing a page address like 127.11.92.785 in order to get to the desired resource is not so convenient (let alone remembering all these combinations). Therefore, at one time, a unique domain name system was developed that made it possible to enter the address as we see it today (in English).

But even here there is its own hierarchy. It also has several levels. For example, international top-level domains include resources independent of the country identifier (GOV - government, COM - commercial, EDU - educational, NET - network, MIL - military, ORG - general organizational, not related to any of the above types) .

The following are resources that explicitly indicate the country identifier. For example, US - USA, RU - Russia, UA - Ukraine, DE - Germany, UK - Great Britain, etc. In addition, such domains have their own sublevels like COM.UA, ORG.DE, etc. In their own turn, and here you can find a clearer link at lower levels (KIEV.UA, KIEV.COM.UA, etc.). In other words, when looking at the address, you can immediately determine not only the country, but also the territorial affiliation of the resource within it.

Basic Internet services

As for the services that can be found on the Internet today, in their categories they are divided into email, news and mailings, file-exchange networks, electronic payment systems, Internet radio and television, web forums, blogs, social networks, online stores and auctions, educational Wiki projects, video and audio hosting, etc. Since social networks have become the most popular recently, let’s look at their structure.

Structure of Internet social networks

A common feature of such an online community is its independence from territorial location or citizenship. Each user creates his own profile (image, place of residence on the Internet, whatever you want to call it), and communication is carried out using an instant messaging system, but not through chat, but in private mode. The only thing comparable to chat is the comment system. In addition, any registered resident of such a community can leave so-called posts, share with the public some materials or links to other publications, etc.

The structure of the Internet is such that when certain protocols are used, such as TCP/IP and IRC, all this is done quite simply. The main condition is registration (creating a login and password to log in), as well as indicating at least minimal information about yourself.

It is not surprising that personal websites and chat rooms are slowly but surely disappearing into oblivion. Even once popular “dialers” like ICQ or QIP cannot withstand any competition, because social networks there are many more possibilities.