Internet - communications and Web-technologies. What is the modern Internet? Basic services on the Internet

Information technology is constantly increasing its influence on all spheres of public life. The last third of the 20th century became the era of the third machine revolution, or the third industrial revolution (if the first is the appearance of the steam engine, and the second is the appearance of electricity and the engine). internal combustion). Electronic computers connected in a network have revolutionized not the methods of converting matter (as in the first two technological revolutions), but the methods of converting information, that is, processing and transmitting data. Today, human intellectual activity and the total intellectual resource are increasingly acting as a machine resource of computer networks, tending to global coverage.

Internet technologies are widely used in various fields of activity modern society and, of course, first of all, in the information sphere. They allow you to optimize a variety of information processes, ranging from the preparation and publication of printed materials and ending with information modeling and forecasting of global processes in the development of nature and society.

Analyzing the role and importance of Internet technologies for the current stage of development of society, we can conclude that this role is strategically important, and the importance of these technologies will increase rapidly in the near future. It is these technologies that today play a decisive role in the field of technological development of society.

Among the distinctive properties of information technologies that are of strategic importance for the development of the economy and society as a whole, there are seven most important ones.

1) Internet technologies make it possible to activate and effectively use the information resources of society, which today are the most important strategic factor in development. Experience shows that the activation, dissemination and efficient use of information resources allows you to get significant savings in other types of resources - raw materials, energy, minerals, materials and equipment, human resources, social time.

2) Internet technologies make it possible to optimize and in many cases automate information processes, which in recent years have taken an increasing place in the life of human society. It is known that the development of a civilized society takes place in the direction of the formation of the information society and information technologies, where the objects and results of labor are mainly not material values, but knowledge and information. Already at present, in most developed countries, the bulk of the developed population is employed to some extent in the preparation, storage, processing and transmission of information products and services.

3) The use of Internet technologies is an element included in more complex production and social processes. Therefore, Internet technologies often act as components of the corresponding production and social technologies.

4) Internet technologies today play an extremely important role in ensuring information interaction between people, as well as in the systems for preparing and distributing mass information. The current distribution problem

information about a product or service, the transfer of an information product is practically solved. Now the role of administrative and state borders has been practically changed. Borders no longer have such a big influence in the information realm, as the dissemination of information occurs almost without restrictions.

5) Internet technologies today occupy a central place in the process of intellectualization of society and the economy. Practically in all developed countries computer and television equipment, educational programs and multimedia technologies are already becoming familiar attributes of everyday life. The use of Internet technologies is becoming a basic structure at any economic level, allowing you to constantly improve the level of skills of existing personnel.

6) Information technologies currently play a key role also in the processes of obtaining and accumulating new knowledge. Most of this knowledge acts as an economic good, the use of which increases the efficiency of economic processes occurring both within an individual enterprise and throughout the entire globe.

7) The importance of the development of Internet technologies for the present stage of the development of society is fundamentally important in that their use can have a significant impact on solving the main problems of the economic development of society. The implementation of these properties by Internet technologies allows the economies of the countries of the world to develop actively. But at the same time, the introduction of Internet technologies into the internal space of any company is a rather complicated process. This is due primarily to the fact that Internet technologies themselves are a complex system, which can be considered from several points of view.

The components of Internet technologies can be considered from two points of view: physical and logical.

The physical components of Internet technology include:

1) Internet

 TCP/IP protocols. IP addresses

 Hierarchical Domain Name System of the Internet

 Internet backbone. Routing.

2) Computers (servers and clients) on the Internet

 Servers Email

 Web servers.

 FTP servers.

 Teleconferencing servers.

 Instant messaging servers.

3) Software on the Internet

 Network operating systems.

 Special software for connecting to the Internet.

 Application protocols.

4) Internet access

 Connecting the NIC to the local network.

 Ethernet cable systems.

 Remote access to global networks.

 Access "computer - network".

 Network-to-network access.

5) Digital communication lines

 Choice of provider. Internet connection

Internet technologies in the physical sense are a set of interconnected user computers, local area networks of organizations and node servers interconnected by various communication channels, as well as special software that ensures the interaction of all these tools in the "client-server" system, based on a single standard protocols.

Consideration of Internet technologies in the physical sense makes it possible to evaluate material values, physical components, due to which the potential of new technologies is realized within the framework of the network structure. It is thanks to the presence of Internet technologies in the physical aspect of their existence that the subsequent economic development of individual companies, regions, countries, groupings of countries became possible. But besides the physical aspect of the existence of Internet technologies, there is also a logical one. Internet technology in a logical sense is a global Information system supporting set storage electronic documents and remote access to them via telecommunications networks; single information space; virtual information and computing environment.

Logic Components Internet Technology

1) Internet services

 Email. Teleconferencing systems.

 World Wide Web - World Wide Web.

 File transfer (FTP).

 Instant messaging (ICQ).

 Interactive chat (chat).

 Audio and video conferences.

2) Information resources on the Internet

 Addressing, URL and data transfer protocols.

 Web pages and Web sites, portals. Web - space.

 Creation of web pages. Web publishing languages.

 Publications on the Internet. Representation.

3) Work on the Internet

 Browsers.

 Navigating the Internet. Search engines.

 Viewing a Web page in a browser.

Consideration of Internet technologies in a logical sense allows us to single out those elements of the information field that have a direct impact on the activities of economic agents. The distribution of information flows creates conditions for the implementation of new global projects. At the same time, the main logical components of Internet technologies are being unified, which creates additional terms processes of economic globalization.

Lecture 2 The Internet and its principles of organization

On October 24, 1995, the Federal Network Council (FNC) approved a resolution defining the term "Internet". It reads: The Federal Network Council recognizes that the following phrases reflect our definition of the term "Internet". The Internet is a global information system that:

 logically interconnected by the space of globally unique addresses based on the Internet Protocol (IP) or subsequent extensions or successors to IP;

 capable of supporting communications using the Transmission Control Protocol/Internet Protocol (TCP/IP) family 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 communication and other related infrastructure described here.

The Internet is a complex technical entity that has the properties of self-organization and self-regulation, on which the high stability of the Internet is based in a technical, economic, social and political sense. It is technically impossible to point out any sector of the Web, the failure of which would disrupt the functioning of the Internet as a whole.

The growth and development of the Internet occurs simultaneously and is balanced in three directions, corresponding to three main components:

- hardware

- software

- informational

The hardware component of the Internet provides the network with technical means (NET-architecture) and includes:

 computers of different models and systems;

 data transmission channels;

 interface devices (electronic and mechanical) of personal computers and data transmission channels.

An analog of the hardware component of the Internet can be considered federal and regional networks highways. The failure of a particular section of the motorway between points A and B should not impede the movement of traffic between these points, because there is always a bypass route.

Unlike the road network, the Internet has not a flat, but a spatial structure, in which data transmission can occur not only through cable communication channels, but via satellite communication channels, radio relay systems, cable television broadcasting lines, etc. That is why the characteristic feature The Internet is resilient to destruction - if some damage or malfunction occurs in some parts of the network, messages can be automatically transmitted along other paths.

This turned out to be possible thanks to the concept laid in the basis even when the network was created, based on two main ideas: the absence of a central computer (all computers on the network are equal) and the packet data transfer method over the network.

The software component of the Internet provides interoperability because it allows data to be converted so that it can be transmitted over any communication channel and played back on any computer. Programs monitor compliance with uniform protocols, ensure the integrity of transmitted data, monitor the state of the Network, and in case of detection of affected or overloaded areas, promptly redirect data streams.

The main functions of the software component:

 ensuring the joint operation of technically incompatible equipment;

 monitors compliance with uniform protocols;

 monitors the state of the network;

 Provides functions for storing, searching and reproducing information.

The information component of the Internet is represented by network documents, i.e. documents stored on computers connected to the Internet. These are text, graphics, sound and video documents. A characteristic feature of the information component is its distribution. For example, when viewing a book stored on the Internet, text may come from some sources, sound and music from others, and graphics from still others. In this way source documents stored on the network are interconnected by a flexible system of links. As a result, we can say that a certain information space is being formed, consisting of hundreds of millions of interconnected documents, resembling a web.

And so, the information component provides various users with a variety of information, as well as its accumulation, storage, modification and redistribution. A characteristic feature of the information component is its distribution (WEB - architecture).

Internet from a technical point of view

From a technical point of view, the Internet is a worldwide computer network, that is, a network that links millions of computing devices into a single whole through communication channels.

Any computing device permanently connected to a local or global network called Host (from the English host - the owner who receives guests). The term "computing device" should be understood not only as desktop personal computers, but also so-called servers that store and transmit information presented in the form of, for example, web pages or e-mail messages, PDA (Personal Digital Assistant) mobile devices ), televisions, mobile computers, cars.

The hosts are connected to each other by communication lines. For such communication, hosts must have special devices that could be connected to communication channels - network interfaces. Network interfaces can be a variety of devices. The best known are Ethernet network cards and modems for conventional dial-up telephone lines.

Hosts are not always directly connected to each other by a single physical link. On the contrary, a typical situation is when communication is carried out using many serial lines connected by special switching devices - routers. If a normal host has one network card installed, then a router has two or more network interfaces.

The software of a computer with several network interfaces must make a decision about which cable system should send the information that arrived through a particular network interface - choose a route for the information. Hence the name for such computers is routers. Routers can be ordinary personal computers, but more often they are specialized computers - Unix machines that have neither a display nor a keyboard. The main function of a router is fast routing, so specialized routers are not cheap.

The router receives a piece of data transmitted on one of its input links and then redirects it to one of its output links. In the terminology of computer networks, the transmitted portions of data are called packets.

The sequence of communication channels and routers through which the packet passes in the course of transmission is called the route, or path, of the packet in the network. The path of the packet is not known in advance and is determined directly during the transmission process. The Internet does not provide a dedicated route for each pair of hosts, but instead uses packet switching technology, whereby different pairs of hosts can use the same route or part of a route at the same time.

The Internet consists of separate sets of communication lines and routers that have well-defined connection points (interfaces) with other such sets. Expensive routers, just like cables, satellite and other communication channels, must have an owner.

In technical language, such a well-defined collection of lines of systems and routers (not quite strictly) is called an autonomous system.

One or more autonomous systems are managed by a single organization called an Internet Service Provider, or ISP (Internet Service Provider), a provider of access to Internet services. ISPs are categorized as residential (such as AOL or MSN), university-based (Stanford University), and corporate (Ford Motors). The ISP provides a network of routers and communication lines. As a rule, Internet providers offer several ways to connect to the Internet (Fig. 1). In addition, ISPs provide a direct connection to a network of websites.

The choice of the way to connect to the Internet depends not only on the technical capabilities of the personal computer, but also on the technical capabilities of the provider. Here it can be said that we are talking not about connecting to the Internet as something virtual, but specifically about connecting to a provider, to the provider's equipment.

Ways to connect to the provider's equipment are wired and wireless. More details will be discussed below.

Local ISPs connect to national or international ISPs such as UUNet and Sprint to provide connectivity between remote users and to provide users with access to information stored on the Internet. The latter use high-speed routers connected by fiber optic cables. Each of the ISPs, both the lower and upper tiers, is an administrative unit that transmits data over the Internet Protocol (IP) and adheres to the naming and address conventions accepted on the Internet.

There are several thousand Internet service providers around the world. Thus, organizationally, the Internet is a large cooperative, and the provider commercial activity. Providers, interacting with each other as commercial organizations, conclude commercial contracts with each other. The subject of such a commercial contract is information, more precisely, the volume of transmitted information per unit of time (the so-called traffic).

Each provider has its own backbone network, or backbone (Backbone (English) - literally - the backbone). On fig. 2, we have conventionally depicted the backbone network of a certain ISP-A provider. Its backbone network is shown in green.

Figure 2 - Scheme of connecting a home computer to the Internet

Typically, ISP providers are large companies that in a number of regions have so-called points of presence (POP, Point of Presence), where local users connect.

Usually a large provider has a point of presence (POP) in several major cities. In each city there are similar modem pools to which local clients of this ISP in this city are connected (to which they call). A provider may lease fiber optic lines from the telephone company to connect all of its Points of Presence (POPs), or it may install its own fiber optic lines. The largest communication companies have their own high bandwidth channels.

Obviously, all ISP-A clients can communicate with each other over their own network, and all ISP-B clients can interact with their own, but if there is no connection between the ISP-A and ISP-B networks, the clients of company "A" and the clients of the company " B" cannot communicate with each other. To implement this service, companies "A" and "B" agree to connect to the so-called access points (NAP - Network Access Points) in different cities, and traffic between the two companies flows over networks through NAP. On fig. Figure 2 shows the backbone networks of only two ISPs. Connecting to other backbone networks is similarly organized, resulting in an association of many high-level networks.

Association and coordination of networks is carried out through bridges and gateways.

Gateway - a computer or program designed to translate data received on one network into a format accepted on another network.

Bridge - if two networks that use the same protocols are connected.

Firewall (Firewall, Firewall) - a set of hardware and / or software that controls and filters network packets passing through it in accordance with specified rules. The main task is to protect computer networks or individual nodes from unauthorized access.

Today, there are many companies that have their own core networks (backbones) that communicate using NAP with the networks of other companies around the world. Thanks to this, everyone who is on the Internet has access to any of its nodes, regardless of where it is located geographically (Fig. 3).

Since it is impossible to schematically reflect the entire set of Internet networks, it is often depicted as a blurry cloud, highlighting only the main elements in it: routers, points of presence (POP) and places of access (NAP).

The speed of information transfer in different parts of the Network varies significantly. Trunk lines, or backbones, connect all regions of the world (Fig. 4) - these are high-speed channels built on the basis of fiber-optic cables. Cables are designated OC (optical carrier), such as OC-3, OC-12 or OC-48. So, the OC-3 line can transmit 155 Mbps, and the OC-48 - 2488 Mbps (2.488 Gbps). At the same time, receiving information on a home computer with a 56K modem connection occurs at a speed of only 56,000 bps.

In fact, the World Wide Web is a complex web of smaller local networks. Imagine a modern road superhighway between big cities, from which smaller roads branch off, connecting small cities with each other, whose inhabitants travel along narrow, slow country roads. These super-high-speed roads for the Network is the high-speed Internet, the so-called "backbone" - backbone networks or trunk lines. Connected to the backbone computers are smaller networks serving specific geographic regions—regional networks to which LANs or even individual computers are attached.

The section of the communication line connecting the end (client) equipment with the access node of the provider (communication operator) in the provider is called the last mile. The abundance of last mile technologies makes it possible to connect any subscriber in a variety of ways - both wired and wireless.

Wired technologies are divided into cable types:

- Telephone line. For a computer to access the Internet, the telephone line is connected to a modem (internal or external), a special device that connects the computer to the telephone line. Internal modem - is an electronic board that is located inside the system unit. The internal modem is cheaper than the external one, however, it is inferior in terms of information transfer speed and ease of use. An external modem is a separate device that connects to a computer. An external modem is more expensive than an internal modem, transmits information faster, and provides greater convenience. Internet access service via telephone lines is implemented using Dial-Up or ADSL technologies. Dial-Up technology or dial-up modem connection to the Internet via analog subscriber line telephone network assumes that the user, each time to access the Internet, dials using a modem telephone line to the provider's modem pool, which in turn leads to a busy telephone line while on the Internet. The connection speed via dial-up lines is up to 56 Kb/sec. ADSL technology allows (thanks to special equipment at the ATC) to organize a high-speed digital channel from a slow analog telephone line, which provides Internet access at speeds up to 7.5 Mbps. Unlike conventional modems that use dial-up access (dialing to a provider's multi-channel pool), the ADSL modem belongs to the category of always-on. The principle of operation of an ADSL modem is that the bandwidth of the telephone wire is divided into three independent streams: one for the phone and two for the Internet (for incoming and outgoing data). That is why, in fact, you can use both the phone and the Internet at the same time.

 Coaxial cable (network cable television). With this connection, a special cable modem is also used, which sends and receives signals over the cable television network. A computer equipped with a cable modem connects to a cable TV network in the same way as a television. On the one hand, the cable modem is connected to a computer through a network card, and on the other hand, through a standard subscriber outlet, it is connected to a television cable network. The difference between telephone and cable modems is in their power / throughput. Since telephone networks are designed to transmit only voice signals, the bandwidth of the frequency range is quite limited. The cable television network is designed to transmit a full video image and has a large bandwidth. This advantage allows you to transfer more information per second - speed.

- Twisted pair and fiber optic cable(highlighted line). It requires organizing a digital communication channel separate from the telephone line between the personal computer and the network node of the Internet provider. The provider runs a dedicated line (twisted pair or fiber optic) of an Ethernet network cable to the subscriber's computer and issues a range of IP addresses for the subscriber to access the Internet. Ethernet belongs to the class of broadband (broadband) technologies. It provides data transfer rates from 10 to 100 Mbps. Dedicated Internet connection supports Ethernet, ADSL and SDSL technology.

Wireless connection is divided into frequency ranges (lengths) of radio waves:

- Satellite channel. This is a way to connect to the Internet using satellite technology. There are two

access options: one-way (asymmetric) and two-way

(symmetric). One-way (asymmetric, asynchronous) satellite Internet is a type of Internet access in which

all incoming information that enters the user's computer is transmitted through a satellite dish, and requests for it

receiving and other outgoing information go through another Internet channel (usually a mobile phone that uses GPRS technology is used for this). That is, a satellite dish for one-way Internet can only receive a signal, but cannot radiate it.

Two-way satellite Internet (VSAT) is characterized by absolute independence from terrestrial communication channels, since the signal is received and transmitted via satellite.

To connect the "satellite" Internet, you need equipment: a satellite dish, a satellite modem and a converter for signal conversion. Most often, satellite Internet is called an asynchronous (or combined) access method - data is received by the user through a satellite dish, and requests (traffic) from the user are transmitted by any other connection - GPRS or terrestrial channels (ADSL, dial-up). The main requirement for the request channel is the reliability of the connection. In most cases the best choice for it is an ADSL connection with free outgoing traffic.

- Radio channel. Wireless communication, or communication over a radio channel, is carried out using RadioEthernet technology and provides for the organization of wireless communication in a limited area with the provision of equal access to a common radio channel for several subscribers. Radio-Ethernet got its name because, according to the protocols used, it is similar to the usual Ethernet protocol, only data is transmitted not via cable, but via radio channels. The channel can be oriented to work in two bands - 915 MHz and 2.4 GHz. The disadvantage is the dependence of the quality of communication on meteorological conditions, radio interference, the problem of direct visibility of the base station, the maximum distance between the points of the subscriber and the provider (with an amplifier for the antenna) is about 60 km.

 Mobile Internet (Cellular networks) is a connection via a mobile phone or a wireless modem to subscribers whose location changes. Mobile telephony, with some exceptions, is carried out through cellular networks - a cellular communication system that is built in the form of a set of cells or cells covering the service area. At the center of each cell is a base station serving all radiotelephones within its cell. Each base station covers a limited area, but in combination they form a continuous coverage. When a subscriber moves from one cell to another, his service is transferred from one base station to another. In Russia, 2 mobile communication systems CDMA and GSM are used, which operate in a certain standard. The cellular communication standard is a system technical parameters and agreements to ensure the functioning of the cellular communication system on a specific radio frequency.

An important factor in the development of mobile communications is the improvement of technologies based on the digitalization of networks. Cellular communication technologies have 4 generations and are designated by the letter “G” (“generation” - generation):

 1G – analog communication standard (frequency range from 453 to 468 MHz),

 2G - digital cellular communication (frequencies 900 and 1800 MHz),

 3G - broadband digital cellular communication combines high-speed Internet access and a data transmission channel for radio communications (UHF frequencies of about 2 GHz).

 4G - based on packet data protocols (over the entire frequency spectrum from 700 MHz to 2.7 GHz).

Each generation contains about a dozen technologies and communication standards.

If the first generation mobile networks (1G - 80s) allowed only voice transmission, then the second generation of cellular communication systems (2G - 90s), based on the GSM standard, also provided other "non-voice" services: the transmission of short text messages - SMS and limited access to the Internet. But both the first (1G) and the second (2G) generation of mobile communication networks were built like wired telephone networks based on circuit switching technology.

Access was carried out through a voice channel and only to those adapted for cell phones Internet pages, so-called WAP sites, written in WML. This used circuit-switched data (CSD) technology, which can be compared to dial-up because it also occupies the channel used for voice traffic and, as a result, blocks the line for a call while connected to the Internet. At a low access speed, payment is made per second at the rate of a regular telephone conversation.

In order to provide full-fledged high-speed access to the Internet without occupying a telephone line, GPRS technology was created in 1997, which implements a packet data transfer method. When using GPRS, information is collected in packets and transmitted through currently unused voice channels. The principle of separation of channels for voice and data transmission made it possible, when accessing the Internet, to pay not for the duration of the connection, but only for the volume of transmitted and received data, i.e. traffic. Traffic is understood as the amount of information transmitted over the network for a certain period of time. Priority traffic in a single channel is the transmission of voice messages. The congestion of the network with voice traffic leads to the emergence of a queue for the transmission of packets, and, as a result, a decrease in the speed of access to the Internet. In general, the speed of Internet access in mobile networks of the second generation depends on: the model of the telephone set, the congestion of the 2G network with voice and Internet traffic, and interference on the radio signal path (physical obstacles - for example, reinforced concrete buildings, passing vehicles, etc.). Max speed in 2G networks can only be received on a quiet windless moonlit night in the field, sitting alone under the base station).

Third generation mobile networks (3G - 2001) are characterized by a shift from narrowband services offered today by GSM and GPRS network operators to multimedia broadband (at speeds up to 2 Mbps) services, including video streaming, mobile Internet, mobile business applications and etc. The third generation mobile network is understood as an integrated mobile network that provides: for fixed subscribers, the information exchange speed is at least 2048 kbps, for subscribers moving at a speed of no more than 3 km/h - 384 kbps, for subscribers , moving at a speed of not more than 120 km / h - 144 kbit / s. With global satellite coverage, 3G networks must provide an exchange rate of at least 64 kbit / s. According to the concept of 3G networks development, the main income of cellular operators in third generation networks will not be from the provision of communication services, but from the use of additional services by subscribers.

Mostly 3G mobile networks are represented by the UMTS standard ( universal system mobile telecommunications), which was developed for the modernization of GSM networks. The UMTS standard is based on CDMA code division multiple access technology, which allows subscribers to use the entire channel width. That is why the 3G generation is called networks with mobile broadband (broadband - broadband transmission) access, allowing you to simultaneously receive ("download") and transmit ("download") information (signals) of various services, for example, data, voice and video .

The main difference between 3G and second generation networks is the transition from narrowband services to multimedia broadband, individualization, that is, the assignment of an IP address to each subscriber, like the Internet, and the permanent stay of subscribers in the network. Territory coverage by third-generation cellular networks is inferior to coverage by 2G networks. The deployment of 3G networks requires the construction of additional base stations, which is associated with a decrease in their range compared to existing GSM networks.

However, the main hopes of market participants are connected with the fourth generation of mobile communications (4G - 2008), as the next stage in the development of wireless telecommunications, which will allow reaching data transfer rates of up to 1 Gb / s in stationary applications and up to 100 Mb / s in data exchange conditions. with mobile access devices. 4G technology, in particular, will allow subscribers to watch high-definition multi-channel TV broadcasts and control home appliances using a mobile device, make cheap intercity

phone calls. 4G communication systems are based on packet data transfer protocols. IPv4 protocol is used for data transfer, and IPv6 support is planned in the future. From a technical point of view, the main difference between fourth generation and third generation networks is that 4G technology is completely based on packet data transfer protocols, while 3G combines both packet switching and circuit switching. The 4G mobile network does not have a channel for voice transmission - 100% of their bandwidth is used for data services.

One of the fourth generation network standards has been approved as LTE as the next mobile broadband network standard after UMTS, which will provide higher data rates and open the way for innovative services requiring high bandwidth. Operators position LTE as a further development of GSM while maintaining backward compatibility. For LTE, this is an obvious advantage, since the operators interested in it have impressive financial capabilities and well-established relationships with users.

A number of analysts call LTE as the main 4G standard, followed by Wi-Fi and WiMax technologies, which imply integration into a single wireless network of a wide range of devices. Mobile WiMAX (Worldwide Interoperability for Microwave Access), an IEEE standardized broadband wireless technology that complements DSL lines and cable technologies as an alternative solution to the long-distance "last mile" problem. WiMAX technology can be used to implement "last mile" broadband connections, deploy wireless access points, organize high-speed communication between company branches and solve other similar problems. If the LTE standard serves as an evolution of existing networks, then WiMAX requires the construction of a new network.

In order to connect to mobile internet you need a modem that provides an Internet connection on a mobile network. The modem can be:

- USB devices

 Mobile phone with support for GPRS and EDGE protocols and means of communication with a computer - USB cable, Bluetooth, infrared port

- Internet access can be carried out with mobile phone, smartphone or tablet thanks to the built-in modem

All modems can be divided into two main categories - universal and operator. Universal modems are independent of specific operators, and any SIM card can be inserted into them. Carrier modems are tuned to the frequency of the cellular operator and depend on generation technologies cellular network that supports cellular

operator. Relatively old phones are connected using slow and expensive GPRS technology, and modern phones operating in third (3G) and fourth (4G) generation cellular communication standards use faster ones: CDMA, UMTS, LTE, WiMAX, for which, as an alternative, it is possible using a USB modem. The quality of communication and the speed of data transfer largely depend on the distance to the base station of the cellular operator, which supports higher generation standards and provides coverage for mobile Internet access.

 Wi-Fi is a specific type of wireless connection to "access points". An access point is a wireless base station designed to provide wireless access to an existing network (wireless or wired) or create an entirely new one. wireless network. Wireless communication is carried out using Wi-Fi technology. Drawing an analogy, the access point can be roughly compared with the tower of a cellular operator, with the proviso that the access point has a smaller range and communication between devices connected to it is carried out using Wi-Fi technology. The range of a standard access point is approximately 200-250 meters, provided that there are no obstacles at this distance (for example, metal structures, concrete floors and other structures that do not transmit radio waves well). The speed of access to the Internet using Wi-Fi technology is distributed in equal proportions between the clients connected to it, therefore, the more clients connected to the access point, the lower the speed of each of them. Most often, this technology is used as an additional free Internet connection service in public places: cafes and airports. With the advent of 3rd generation mobile networks, free Wi-Fi Internet is also being allocated in transport. For this in public transport a special 3G router is installed, with which it connects to the Internet via a cellular signal and distributes it to passengers via a Wi-Fi access point.

To access the information component of the Internet, your computer must be connected to the global Internet. The computer must have all the software and hardware required to work on the Internet, as well as a physical connection (wired or wireless) of this computer with one of the providers (a company whose computer network is part of the Internet). To search and view information on the Internet, a web browser must be installed on a computer to request web pages from the Internet, process them, display them, and move from one page to another.

Each source of information on the Internet has its own address, which must be entered in the address field of the web browser. For example, to find out if a teacher has given grades for a recent checkpoint, you turn to the site WWW.STUD.SSSU.RU - the information resource of YURGUES.

After you have typed a name and pressed the Enter key, your computer sends a request to the source of information you specified. The request travels over the network until it reaches the computer hosting the website. On this computer, the request is received and served by a special web server program. Browsers act as clients to a web server. In response to an incoming request, the web server of the WWW.STUD.SSSU.RU site transmits information posted on its home page, which displays it on your computer screen.

Principles of organizing communication between computers on the Internet

Let's not look at the Internet as a network, and not a "web" of communication lines and a multitude of transceivers. The Internet network consists mainly of leased telephone lines. It would seem that the Internet is quite similar to the telephone network, and the model of the telephone network adequately reflects its structure and operation. In fact, both of them are electronic, both allow you to establish communication and transfer information. And the Internet also consists, first of all, of leased telephone lines. But this is not so, since the telephone network is a circuit-switched network - when, when a subscriber is called, a physical connection is established with him for the entire duration of the communication session. At the same time, a part of the network is allocated (and occupied) that is no longer available to others (even if subscribers are silent, and other subscribers would like to talk about a really urgent matter). This leads to irrational use of very expensive resources - communication lines.

The Internet is a packet-switched network, which is fundamentally different from a circuit-switched network.

For the Internet, the model of an ordinary state postal service is more suitable. Mail is a packet communication network, where there is no part of this network allocated to the subscriber. The mail message is mixed with the messages of other users, thrown into a container, sent to another post office, where it is sorted again. Although the technologies vary widely, mail is a great and illustrative example of a packet-switched network. The mail model captures the way the Internet works and is remarkably accurate.

On the Internet, all interconnected networks (Ethernet, Token Ring, networks on telephone lines, packet radio networks, etc.) are, in fact, analogues of railways, mail planes, post offices and postmen. Through them mail moves from place to place. Internet routers are like post offices, where they decide how to move data (“packets”) across the network, just like a postal node maps out the path of a mail envelope. Branches or nodes do not have direct connections with all the others. If you send a mail message from city A to city B, the post office will not hire a plane that will fly from the airport closest to city A to the airport in city B. Instead, the local post office sends a message to the substation in the right direction, which in turn, further in the direction of the destination to the next substation. Thus, the letter will gradually approach the destination until it reaches the post office, which is in charge of the desired object and which delivers the message to the recipient. For such a system to work, it is required that each substation knows about the existing connections and about which of the nearest substations should optimally transmit a packet addressed there. About the same in the Internet: routers answer the route of sending a data packet.

At each postal substation, the next substation is determined, where the correspondence will be sent next, i.e. there is a further path (route) planned - this process is called routing. For routing, each substation has a table where the destination address (or index) corresponds to the indication of the postal substation where this correspondence should be sent next. Their network counterparts are called routing tables. These tables are distributed to postal substations centrally by the respective postal division. From time to time instructions are sent out to change and supplement these tables. In the Internet, the compilation and modification of routing tables are defined

corresponding rules - ICMP (Internet Control Message Protocol), RIP (Routing Internet Protocol) and OSPF (Open Shortest Path First) protocols. The nodes involved in routing are called routers.

Postal items (letter, package, parcel) sent as part of the postal exchange must meet certain requirements for its maximum weight, allowable attachment and size limits.

The Internet also has a set of rules - protocols for handling transmitted information, which, due to equipment limitations, is divided into parts (by byte boundaries), decomposed into separate packets. The length of information within a packet is typically between 1 and 1500 bytes. This protects the network from monopolization by any user and gives everyone approximately equal rights. For example, consider the following situation: how to send a book by mail if it only accepts letters and nothing more? The obvious method is to simply tear the book into pages and send them in separate envelopes. The recipient, guided by page numbers, can easily restore the book. The transmission scheme for this case is shown in fig. 5.

Protocols define how data from an application is broken down into packets for transmission over a cable and what electrical signals represent data on a network cable. In a broad sense, a protocol is a predetermined rule (standard) according to which one who wants to use a certain service interacts with the latter. In relation to the Internet, a protocol is a rule for the transmission of information on the Web.

Two types of protocols should be distinguished: basic and application. The underlying protocols are responsible for the physical transfer of messages between computers on the Internet. Application protocols are called higher-level protocols, they are responsible for the functioning of specialized services, for example, for the transmission of hypertext messages, files, e-mail.

A set of protocols of different layers working simultaneously is called a protocol stack. Each lower level of the protocol stack has its own system of rules and provides a service for the higher ones.

This interaction can be compared to the forwarding scheme of a regular letter. For example, the director of firm "A" writes a letter and gives it to the secretary. The secretary places the letter in an envelope, writes the address and takes the envelope to the post office. The post office delivers the letter to the post office. The post office delivers the letter to the recipient - the secretary

director of firm B. The secretary opens the envelope and sends the letter to the director of the company "B". Information (letter) is transferred from the upper level to the lower one, acquiring at each stage additional service information (package, address on the envelope, postal code, container with correspondence, etc.), which is not related to the text of the letter.

The bottom level is the level of the postal transport that transports the letter to its destination. At the destination, the reverse process occurs: the correspondence is retrieved, the address is read, the postman carries the envelope to the secretary of firm B, who takes out the letter, determines its urgency, importance, and, depending on this, passes the information above. The directors of firms "A" and "B", passing information to each other, do not care about the problems of sending this information, just like a secretary does not care how mail is delivered.

Likewise, each protocol in the protocol stack performs its own function without concern for the functions of the protocol at another layer.

Internet technologies network infrastructure

A wire can only send bits from one end to the other. The Internet, on the other hand, will move data to various locations around the world thanks to the network (internet) layer in the ISO OSI reference model.

The OSI model, also known as the Open Systems Interconnection (OSI) model and developed by the International Organization for Standardization (ISO), divides network connectivity into seven layers, for which standard names and functions are defined.

The OSI model is based on two key principles:

1. The concept of open systems. Each level of the model has strictly defined network functions. This means that two different network systems that support the functions of the respective layer can communicate at that layer.

2. The concept of a peer-to-peer connection of the "point-to-point" type. The data generated at a particular level of the model is intended only for the corresponding level of another device. In other words, in order to perform the network functions assigned to them, the intermediary levels do not change "foreign" data, but simply add their own information to the data found in the packet.

In an attempt to streamline the approach to considering network protocols, the International Standards Organization (ISO) has created a seven-layer model that defines the basic functions of a network, called the OSI Reference Model.

Module 2: Basic Internet Communications and Web Technologies

Topic 5. Network Internet communications

Lecture number 9. Internet communications: FTP, E-mail, instant messengers, IP telephony

Lecture number 10. Digital broadcast systems

Topic 6.
Web technologies

Lecture number 11. Technology for creating Internet nodes

Lecture number 12. Programming languages

Lecture number 13. Website development

Topic 7.
Cloud technologies

Lecture number 14. Cloud computing.

Topic 8. WEB-communication services of real time

Lecture number 15. WEB communications and communication cloud Web services based on WebRTC

Topic 9. Modern telecommunication technologies of the Internet of things IoT

Lecture number 16. Architecture, protocols and wireless technologies of IoT

Basic Internet Communications and Web Technologies

Topic 5. Network Internet communications

Basic services on the Internet

The servers of the global Internet host different kinds information: files, web documents, audio and video recordings. The most common network services on the Internet that are provided by Web servers on the network include:

Word Wide Web (WWW) - the World Wide Web or a distributed system of hypertext documents interconnected by hyperlinks;
FTP - file transfer service;
E-mail E-mail - an offline electronic messaging service;
Messengers (ICQ, Skype, Miranda IM, etc.) - services for instant messaging, voice communication and video communication on the Internet online;
VoIP services (Voice-over-IP - voice transmission in IP networks) are services that are designed to make Internet calls to regular phones;
Telnet - a service for accessing computers in remote terminal mode;
USENET, News - teleconferences, newsgroups (bulletin boards) or discussion groups on various topics;
Archie - data and program search service;
Gopher - information access service using hierarchical catalogs (hierarchical menus);
WAIS (WAIS implements the concept of a distributed information retrieval system) keyword data retrieval service;
Whois - address book Internet networks. Upon request, the user can obtain information about the owners of domain names;
Streaming is a service for transmitting and playing video or sound in parts. To view streaming video from video hosting, various options for web players are used.

Internet network services can be divided into two categories:

services that use network databases;
services that exchange information between network subscribers.

Almost all Internet services are built on the client-server principle. A server on a network is a computer or program capable of providing certain network services to clients at their request. Client programs include:

browsers - client programs (application programs) provide access to almost all Internet information resources that are stored on Web servers;
ftp clients;
telnet clients;
mail clients;
WAIS clients;
Gopher is a client program and so on.

GBPOU KK

"Krasnodar Assembly College"

LECTURE:

Modem. Units.

Internet technologies.

Teacher

information technologies

Nesmelova A.R.

Krasnodar2015

Modem. Units.

Internet technologies.

Explanatory note

Given Toolkit is designed to study theoretical knowledge on the topic “Modem. Units. Internet technologies." in the course of the discipline "Informatics and ICT" for the first courses of technical specialties, focused on the implementation of the federal component of the state educational standard (hereinafter - GEF) of secondary (complete) general education in informatics at the basic level within the main educational program secondary vocational education, taking into account the profile of the vocational education received.

The content of the main sections of the lecture:

Introduction

Modem

Units

History of the Internet

Offline technologies

Online technologies

Conclusion

Target: familiarization of students with the theoretical foundations of the creation and operation of the Internet, the disclosure of the basic concepts of the global network, the study of the features various internet technologies.

Tasks: give the concept of the Internet and study its capabilities, basic means and methods of organizing communication, compare the features of various Internet technologies, study the basic units of measurement of data transfer speed, learn how to calculate the amount of information transmitted

Introduction

The Internet is a worldwide system of computer networks that are interconnected and operate using data packet routing and protocols.IP. Based on the Internet, a global information space has been formed andWorldWideweb(The World Wide Web). By the way, very often the Internet is also called the World Wide Web, but this is erroneous, since the "Internet" and "World Wide Web" mean completely different concepts. Also, on the basis of Internet technologies, many other data transfer protocols have been created. Without the Internet, the information development of society would not be as rapid and fruitful as it can be observed today. More than 1.5 billion people regularly use the Internet per day, although this figure is very approximate, because every day the number of network users is growing steadily.

Considering the principle of the Internet and, accordingly, answering the question of what the Internet is, it should be noted that its main components are government and home computer networks. To unite all these networks, the Internet protocol was invented (IP) and the principle of data packet routing.

The task of routers at the junction of networks, regardless of whether they are software or hardware, is to automatically sort and redirect data packets based onIP- the address of the recipient of the package. Thanks to the protocolIP, a single address space is formed all over the world, however, its own subspace exists in each individual network. This address organization avoids conflicts between individual networks in a single world space, which allows data to be transmitted smoothly and accurately.

For communication between computers remote from each other, ordinary telephone networks can be used, which to one degree or another cover the territories of most states.Telecommunication - remote data transmission based on computer networks and modern technical means of communication. The only problem in this case is the conversion of digital (discrete) information, with which the computer operates, into analog (continuous).

Modem - a device connected to a personal computer and designed to send information (files) over a network (local, telephone). The modem converts analog information into discrete information and vice versa. The job of a modem modulator is to convert the bit stream from the computer into analog signals suitable for transmission over a telephone channel. The modem demodulator performs the inverse task. A fax modem is a device that combines modem capability and the means to exchange fax images with other fax modems and conventional telefax machines.

Thus, the data to be transmitted is converted into an analog signal by the "transmitting" computer's modem modulator. The receiving modem, located at the opposite end of the line, "listens" to the transmitted signal and converts it back to digital using a demodulator. After this work is done, the information can be transmitted to the receiving computer.

Both computers, as a rule, can simultaneously exchange information in both directions. This mode of operation is called full duplex.

Duplex data transfer mode is a mode in which data transfer is carried out simultaneously in both directions.

Unlike duplex transmission mode,half duplex It implies transmission in only one direction at a time.

In addition to the actual modulation and demodulation of signals, modems can compress and decompress the transmitted information, as well as search for and correct errors that have occurred during data transmission over communication lines.

Units. One of the main characteristics of a modem is the modulation speed, which determines the physical data transfer rate without taking into account error correction and data compression. The unit of this parameter is the number of bits per second (bps), called baud.

Bit per second (English Bits persecond, bps) - the basic unit of measurement of the information transfer rate used at the physical layer of the OSI or TCP / IP network model.

At higher levels of network models, as a rule, a larger unit is used - bytes per second (B / s or Bps, from English bytes per second) equal to 8 bits / s.

Unlike baud (baud; in binary coding, baud also denotes the number of bits per second), bits per second measures the effective amount of information, without taking into account the service bits (start/stop/parity) used in asynchronous transmission. In some cases (with synchronous binary transmission) the baud rate may be equal to the bits per second.

Any communication channel has a limited bandwidth (information transfer rate), this number is limited by the properties of the equipment and the line (cable) itself.

The amount of transmitted information is calculated by the formula Q=q*t, where q is the channel bandwidth (in bits per second), and t is the transmission time.

History of the Internet

The first mention of the Internet as a reliable information transmission system was made by the US Department of Defense in1957 year. The US military was concerned that America should have a system for transmitting military information if there was a war.

All developments were financed by the Ministry of Defense, and as a result, a network appearedARPANET. Over the yearsARPANETimproved, which led to its use in the scientific world, but for the first timeARPANETwas installed at the University of California, Los Angeles,1969 year, 2 September. Almost two months passed between the installation of the first server and its first launch. The second server of the network was installed at the Stanford Research Center, and the distance between the two servers was 640 kilometers.

At 9PM,October 29, 1969 year, the first attempt was made to transfer data from the first server to the second. Of course, not everything went smoothly usingARPANET, in particular, the launch of the network failed the first time - scientists were able to send onlyLOGinstead ofLOGON(meaning "login"). After 1.5 hours, at 22:30 the second attempt was successful. This day can be called the birth date of the Internet.

AT1971 In the year the Americans proposed the first program, which became very popular - it was the first e-mail. In principle, even today the most popular among Internet users is e-mail, but the modern user has the right to choose, as there are several programs on the network for sending e-mails.

AT1973 year the Internet becomes international, because it was in this year that Americans connected to their networkARPANETseveral foreign organizations located in Norway and Britain. The use of the network was mainly based on the forwarding of emails. But at the same time, in the 70s, the first bulletin boards and newsletters appeared. The active development of protocols was indicated by the end of the 70s, the beginning of the 80s, and already in 1983 protocolsIPhave been standardized. Initially, networkARPANETworked on protocolNCP, but thanks to Jon Postel and some other programmers,ARPANETswitched toTCP/ IP, which justified the hopes of its authors, because we use it today. Since 1983 the world has been talking about the networkARPANEThow about the internet.

The term "domain name system" came into use in 1984. At the same time,ARPANETgot the strongest opponent -NSFnet, a network founded by the US National Science Foundation.NSFnetis an extensive inter-university network with more opportunities thanARPANET. NetNSFnetwas able to connect 10,000 computers to itself in a year, which led to the renaming of the network to the Internet. After 4 years, Internet users were able to communicate live, that is, in a chat, thanks to the developed protocolInternetRelayChat.

The British scientist Tim Berners Lee can rightfully be called the "godfather" of the concept of the World Wide Web, since it was this person who proposed the World Wide Web in 1989 at the European Council for Nuclear Research. By 1991, Tim Berners Lee is developingURI, protocolHTTPandHTML. A year earlier, in 1990, the first network ceased to exist, as competition fromNSFnetbecame forARPANETlosing. Since 1990, the Internet has been using a telephone line to connect.

After 20 years, many experts agree that the history of the Internet can be divided into two eras. The first was before the advent of the web browser.NCSAMosaic, which was introduced in 1993; the second - after the appearanceNCSAMosaic. Within a year, the browser allowed the Internet to spread around the world. Since 1995, the World Wide Web has been the main provider of information on the Internet, and by a significant margin, ahead of the file transfer protocol.FTP. The term "World Wide Web" firmly occupies a leading position in 1996, leaving behind the definition of "Internet".

Overview of the main Internet technologies

Internet technologies, as well as industrial or financial technologies, determine the means and form in which Team work people to achieve certain goals.

Internet technologies combine information flows from a large number of actors to achieve greater coherence of their actions, as well as a more precise definition of the content of their future actions. Internet technologies open up new broad horizons for improving communications and information exchange between people on a global scale.

These technologies can be divided into two main categories:

1) offline technologies - means of distributing messages that provide communications in off-line mode (i.e., allowing significant asynchrony in messaging);

2) online technologies of synchronous communications in real time (on-line).

Offline technologies

The most static representative of the first type are classic web pages that carry information (perhaps quite often updated) from the source to the consumer, but do not contain convenient means for two- or multilateral interaction between authors and users of information (in later modifications of the web page technology this shortcoming is gradually being eliminated).

A more dynamic representative of the first type of technology is teleconferences, or as they are also called "newsgroups" (newsgroups), and "mailing lists" close to them, which allow for several hours to distribute messages of individuals among a gigantic audience and give quite convenient opportunities for mass discussions and exchange of opinions.

Let's take a closer look at the three most used ways to implement asynchronous communications:

Mailing Lists (mailing list) are the oldest representative of interactive Internet technologies. To participate in them, it is enough to have your own e-mail address and know the address of the desired mailing list. A letter is sent to this address, the text of which consists of some commands or a message for users of this mailing list. To get a list of commands, as a rule, it is enough to send a single-word help letter to the mailing list address. The header of emails with commands for the mailing list should usually be empty. If you sent a letter with a command to subscribe to this mailing list (most often this command is subscribe), then your address, which is taken from the service headers of your letter, is placed in the list of addresses to which all incoming messages will be duplicated, except for letters with commands.

Newsgroups (newsgroups), in Russia they are more often called teleconferences, are technically more advanced than mailing lists and therefore often include the capabilities of the latter.The main difference between newsgroups and mailing lists is that the user may not receive them on his computer by e-mail, but can view them directly on the so-called news servers (newsserver). This requires special software. Browsing different newsgroups becomes easier and faster than mailing lists. From a technical point of view, newsgroups exist due to the fact that all the world's news servers exchange messages from their users on overlapping lists of newsgroups. Different servers may store different sets of newsgroups for their users and for different durations. For example, the Infoteka news server stores about 1500 newsgroups, and the similar NSU server does not have several hundred groups more. For different groups, the period for storing messages can vary from one day (group "test" in NSU) to several months.

Web forums (web forums)are the next stage in the development of the technologies described above and represent the integration of the capabilities of mailing lists, newsgroups with web pages. As a result, familiar web pages, which are superior to other technologies in terms of expressiveness, receive additionally quite powerful interactive properties.

Online technologies

The second type of technologies that provide synchronous exchange of information in real time include the so-called "talk channels" (chat channels), as well as still little used audio and video conferences. It is estimated that about a third of the time users spend on the Internet is spent on "cyber conversations" carried out using "talk channels". The growing popularity of this technology of "live" communications is explained by its simplicity (the user receives on the screen of his computer the texts of replicas from all participants in the cyber-conversation and can immediately enter his own text, which takes its place in the sequence of replicas of this conversation), a variety of expressive means (except for texts, in the same way, pictures, audio and video clips, etc. can be embedded in the "conversation", as well as the possible anonymity of the interlocutors, which gives such "conversations" liveliness and immediacy. The number of conversational channels is estimated at several thousand, many of which operate around the clock.

Cloud computing is a distributed data processing technology in which computer resources and capacities are provided to the user as an Internet service.

Spline offices are applications implemented using the innovative Internet technology "software as a service" (English, Software as a Service - SaaS), in which the software is created and maintained as a web application on the developer's server, providing users with access to programs through the Internet. Microsoft Office 365 can serve as examples of such offices. Another “Google Docs cloud technology, its functions: creating office documents in the form of text, tables, presentations and dialog forms, providing up to 1 gigabyte of memory with the ability to create a hierarchy of folders and collections for storage files, export-import of documents in known formats (DOC, XLS, ODT, ODS, RTF, CSV, PPT, including MS Office 2007/2010 formats). the ability to save an office document in an HTML version for publication on the Internet, preview and print the document.

However, if the Internet and networks become more accessible, then Internet technologies are complex systems that combine both physical and logical components.

The physical components have material value that allows you to develop business Internet technologies.

The physical elements of Internet technology include:

Network technologies. Servers. data centers;

Internet software;

Topology of the Internet (interaction of computers and servers in the network);

Network services (e-mail, DNS service, FTP protocol, etc.);

Local and home networks, routers.

Logical components allow you to create almost any Internet resource on the network: a website, a web application, a web portal.

Web technologies:

Markup languages (HTML);

Cascading Style Sheets (CSS);

Scripting language (JavaScript);

Browsers;

Web pages DOM (Document Object Model (DOM);

markup languageXML (Extensible Markup Language);

Search engines;

SEO(search engine optimization).

The division into physical and logical components is somewhat arbitrary, because they can only exist in interconnection and do not have a special purpose without each other.

You also need to understand that this is, of course, an incomplete list of Internet technology elements. But it gives a general idea of such a voluminous concept as the Internet technology.

Conclusion.

At present, the Internet is developing exponentially: every one and a half to two years, its main quantitative indicators doubled. This applies to the number of users, the number of connected computers, the amount of information and traffic, the amount of information resources.

The Internet is developing and qualitatively. The boundaries of its application in human life are constantly expanding, completely new types of network services and telecommunication technologies are emerging.

The life of modern society is becoming more and more computerized. The requirements for the efficiency and reliability of information services are growing. Scientists are developing fundamentally new forms of global networks.

Bibliography

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13. Institute of New Technologies

14. Collection of digital educational resources

Lecture 1 Internet technologies: general provisions, types

Information technology is constantly increasing its influence on all spheres of public life. The last third of the twentieth century became the era of the third machine revolution, or the third industrial revolution (if the first is the appearance of the steam engine, and the second - the appearance of electricity and the internal combustion engine). Electronic computers connected in a network have revolutionized not the methods of converting matter (as in the first two technological revolutions), but the methods of converting information, that is, processing and transmitting data. Today, human intellectual activity and the total intellectual resource are increasingly acting as a machine resource of computer networks, tending to global coverage.

Internet technologies are widely used in various spheres of activity of modern society and, of course, first of all, in the information sphere. They allow you to optimize a variety of information processes, ranging from the preparation and publication of printed materials and ending with information modeling and forecasting of global processes in the development of nature and society.

Among the distinctive properties of information technologies that are of strategic importance for the development of the economy and society as a whole, there are seven most important ones.

5) Internet technologies today occupy a central place in the process of intellectualization of society and the economy. In almost all developed countries, computer and television equipment, educational programs and multimedia technologies are already becoming familiar attributes of everyday life. The use of Internet technologies is becoming a basic structure at any economic level, allowing you to constantly improve the level of skills of existing personnel.

The components of Internet technologies can be considered from two points of view: physical and logical.

The physical components of Internet technology include:

1) Internet

 TCP/IP protocols. IP addresses

 Hierarchical Domain Name System of the Internet

 Internet backbone. Routing.

2) Computers (servers and clients) on the Internet

 Email servers

 Web servers.

 FTP servers.

 Teleconferencing servers.

 Instant messaging servers.

3) Software on the Internet

 Network operating systems.

 Special software for connecting to the Internet.

 Application protocols.

4) Internet access

 Connecting the NIC to the local network.

 Ethernet cable systems.

 Remote access to global networks.

 Access "computer - network".

 Network-to-network access.

5) Digital communication lines

 Choice of provider. Internet connection

Consideration of Internet technologies in the physical sense makes it possible to evaluate material values, physical components, due to which the potential of new technologies is realized within the framework of the network structure. It is thanks to the presence of Internet technologies in the physical aspect of their existence that the subsequent economic development of individual companies, regions, countries, groupings of countries became possible. But besides the physical aspect of the existence of Internet technologies, there is also a logical one. Internet technologies in the logical sense is a global information system that supports the storage of many electronic documents and remote access to them via telecommunications networks; single information space; virtual information and computing environment.

Logic Components Internet Technology

1) Internet services

 Email. Teleconferencing systems.

 World Wide Web - World Wide Web.

 File transfer (FTP).

 Instant messaging (ICQ).

 Interactive chat (chat).

 Audio and video conferences.

2) Information resources on the Internet

 Addressing, URL and data transfer protocols.

 Web pages and Web sites, portals. Web - space.

 Creation of web pages. Web publishing languages.

 Publications on the Internet. Representation.

3) Work on the Internet

 Browsers.

 Navigating the Internet. Search engines.

 Viewing a Web page in a browser.

Lecture 2 The Internet and its principles of organization

 logically interconnected by the space of globally unique addresses based on the Internet Protocol (IP) or subsequent extensions or successors to IP;

 capable of supporting communications using the Transmission Control Protocol/Internet Protocol (TCP/IP) family 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 communication and other related infrastructure described here.

The growth and development of the Internet occurs simultaneously and is balanced in three directions, corresponding to three main components:

- hardware

- software

- informational

The hardware component of the Internet provides the network with technical means (NET-architecture) and includes:

 computers of different models and systems;

 data transmission channels;

 interface devices (electronic and mechanical) of personal computers and data transmission channels.

Federal and regional highway networks can be considered an analogue of the hardware component of the Internet. The failure of a particular section of the motorway between points A and B should not impede the movement of traffic between these points, because there is always a bypass route.

This turned out to be possible due to the concept laid in the basis even when the network was created, based on two main ideas: the absence of a central computer (all computers on the network are equal) and the packet data transfer method over the network.

The main functions of the software component:

 ensuring the joint operation of technically incompatible equipment;

 monitors compliance with uniform protocols;

 monitors the state of the network;

 Provides functions for storing, searching and reproducing information.

The information component of the Internet is represented by network documents, i.e. documents stored on computers connected to the Internet. These are text, graphics, sound and video documents. A characteristic feature of the information component is its distribution. For example, when viewing a book stored on the Internet, text may come from some sources, sound and music from others, and graphics from still others. Thus, the primary documents stored on the network are interconnected by a flexible system of links. As a result, we can say that a certain information space is being formed, consisting of hundreds of millions of interconnected documents, resembling a web.

Internet from a technical point of view

From a technical point of view, the Internet is a worldwide computer network, that is, a network that links millions of computing devices into a single whole through communication channels.

Any computing device that is constantly connected to a local or global network is called a Host (from the English host - a host that receives guests). The term "computing device" should be understood not only as desktop personal computers, but also so-called servers that store and transmit information presented in the form of, for example, web pages or e-mail messages, PDA (Personal Digital Assistant) mobile devices ), televisions, mobile computers, cars.

The sequence of communication channels and routers through which the packet passes in the course of transmission is called the route, or path, of the packet in the network. The path of the packet is not known in advance and is determined directly during the transmission process. The Internet does not provide a dedicated route for each pair of hosts, but instead uses packet switching technology, where different pairs of hosts can use the same route or part of a route at the same time.

In technical language, such a well-defined collection of lines of systems and routers (not quite strictly) is called an autonomous system.

The choice of the way to connect to the Internet depends not only on the technical capabilities of the personal computer, but also on the technical capabilities of the provider. Here we can say that we are not talking about connecting to the Internet as something virtual, but specifically about connecting to a provider, to the provider's equipment.

Ways to connect to the provider's equipment are wired and wireless. More details will be discussed below.

There are several thousand Internet service providers around the world. Thus, organizationally, the Internet is a large cooperative, and the provider is a commercial activity. Providers, interacting with each other as commercial organizations, conclude commercial contracts with each other. The subject of such a commercial contract is information, more precisely, the volume of transmitted information per unit of time (the so-called traffic).

Figure 2 - Scheme of connecting a home computer to the Internet

Typically, ISP providers are large companies that in a number of regions have so-called points of presence (POP, Point of Presence), where local users connect.

Association and coordination of networks is carried out through bridges and gateways.

Gateway - a computer or program designed to translate data received on one network into a format accepted on another network.

Bridge - if two networks that use the same protocols are connected.

Wired technologies are divided into cable types:

- Telephone line. For a computer to access the Internet, the telephone line is connected to a modem (internal or external), a special device that connects the computer to the telephone line. Internal modem - is an electronic board that is located inside the system unit. The internal modem is cheaper than the external one, however, it is inferior in terms of information transfer speed and ease of use. An external modem is a separate device that connects to a computer. An external modem is more expensive than an internal modem, transmits information faster, and provides greater convenience. Internet access service via telephone lines is implemented using Dial-Up or ADSL technologies. The Dial-Up technology or modem dial-up connection to the Internet via an analog subscriber line of the telephone network assumes that each time the user accesses the Internet, he dials the telephone line to the provider's modem pool using a modem, which in turn leads to the busyness of the telephone line during time spent on the Internet. The connection speed via dial-up lines is up to 56 Kb/sec. ADSL technology allows (thanks to special equipment at the ATC) to organize a high-speed digital channel from a slow analog telephone line, which provides Internet access at speeds up to 7.5 Mbps. Unlike conventional modems that use dial-up access (dialing to a provider's multi-channel pool), the ADSL modem belongs to the category of always-on. The principle of operation of an ADSL modem is that the bandwidth of the telephone wire is divided into three independent streams: one for the phone and two for the Internet (for incoming and outgoing data). That is why, in fact, you can use both the phone and the Internet at the same time.

 Coaxial cable (cable television networks). With this connection, a special cable modem is also used, which sends and receives signals over the cable television network. A computer equipped with a cable modem connects to a cable TV network in the same way as a television. On the one hand, the cable modem is connected to a computer through a network card, and on the other hand, through a standard subscriber outlet, it is connected to a television cable network. The difference between telephone and cable modems is in their power / throughput. Since telephone networks are designed to transmit only voice signals, the bandwidth of the frequency range is quite limited. The cable television network is designed to transmit a full video image and has a large bandwidth. This advantage allows you to transfer more information per second - speed.

 Twisted pair and fiber optic cable (leased line). It requires organizing a digital communication channel separate from the telephone line between the personal computer and the network node of the Internet provider. The provider runs a dedicated line (twisted pair or fiber optic) of an Ethernet network cable to the subscriber's computer and issues a range of IP addresses for the subscriber to access the Internet. Ethernet belongs to the class of broadband (broadband) technologies. It provides data transfer rates from 10 to 100 Mbps. Dedicated Internet connection supports Ethernet, ADSL and SDSL technology.

Wireless connection is divided into frequency ranges (lengths) of radio waves:

- Satellite channel. This is a way to connect to the Internet using satellite technology. There are two

access options: one-way (asymmetric) and two-way

(symmetric). One-way (asymmetric, asynchronous) satellite Internet is a type of Internet access in which

all incoming information that enters the user's computer is transmitted through a satellite dish, and requests for it

Two-way satellite Internet (VSAT) is characterized by absolute independence from terrestrial communication channels, since the signal is received and transmitted via satellite.

To connect the "satellite" Internet, you need equipment: a satellite dish, a satellite modem and a converter for signal conversion. Most often, satellite Internet is called an asynchronous (or combined) access method - data is received by the user through a satellite dish, and requests (traffic) from the user are transmitted by any other connection - GPRS or terrestrial channels (ADSL, dial-up). The main requirement for the request channel is the reliability of the connection. In most cases, the best choice for him is an ADSL connection with free outgoing traffic.

The subject and objectives of the course Fundamentals of Internet technologies The subject of this course is the technologies of the global network World Wide Web. The course will cover such issues as: The structure and principles of the Web (basic concepts, architecture, standards and protocols); Web technologies (web page markup and programming languages - HTML, CSS and Java. Script, PHP, tools for developing and managing web content and applications for the Web, tools for integrating web content and applications into the Web). The Web is a global information space based on the physical infrastructure of the Internet and the HTTP data transfer protocol. Often, when talking about the Internet, it is the Web that is meant.

History of the Internet Development timeline of the Internet (from 1966 to 2000) Year Event 1966 ARPA control packet switching experiment 1969 First operational nodes on the ARPANET 1972 Invention of distributed email 1973 First computers connected to the ARPANET outside the United States 1975 ARPANET transferred to Department of Defense Communications Administration 1980 Experiments with TCP/IP begin 1981 A new host is added to the network every 20 days 1983 Transition to TCP/IP is completed 1986 NSFnet is created 1990 ARPANET ceases to exist 1991 Gopher is introduced 1991 The World Wide Web is invented. Released PGP system. Mosaic launched 1995 Privatization of the Internet backbone 1996 OS-3 backbone (155 Mbps) built 1998 Number of registered domain names exceeded 2 million 2000 Number of indexed web pages exceeded 1 billion

Standardization on the Internet The result of standardization work is embodied in RFC documents (eng. Request for Comments) - a document from a series of numbered Internet information documents containing technical specifications and Standards widely used on the World Wide Web. Examples of popular RFC documents. RFC 768 RFC 791 RFC 793 RFC 822 RFC 959 RFC 1034 RFC 1035 RFC 1591 RFC 1738 RFC 1939 RFC 2026 RFC 2045 RFC 2231 RFC 2616 RFC 2822 RFC 3501 Subject UDP IP TCP E-mail format, superseded by FTP DNS - concept DNS - concept Implementation Domain name structure URL POP protocol version 3 (POP 3) Internet standardization process MIME Character encoding HTTP E-mail format IMAP version 4 edition 1 (IMAP 4 rev 1)

The W 3 C Consortium is an organization that develops and implements technology standards for the Internet and the WWW. The mission of the W 3 C is formulated as follows: "Unleash the full potential of the World Wide Web by creating protocols and principles that guarantee the long-term development of the Web." The other two major objectives of the Consortium are to ensure the complete "internationalization of the Web" and make it accessible to people with disabilities. W 3 C develops common principles and standards for the WWW, called "Recommendations", which are then implemented by software and hardware developers. Thanks to the Recommendations, compatibility between software products and hardware is achieved. various companies, which makes the WWW network more perfect, versatile and easy to use. All W 3 C Recommendations are open, that is, not protected by patents and can be implemented by anyone without any financial contribution to the Consortium. For the convenience of users, the Consortium has created special validator programs (English Online Validation Service), which are available over the network and can check documents for compliance with the popular W 3 C Recommendations in a few seconds.

The method of analysis of borderline minds The main rules for the method of analysis of borderline minds are: to induce tests for the limit of the multiplier of allowable values of input data and tests with invalid values, which leads to an insignificant outlier for the inter tsієї multiplier. For example, for the multiplier [-1. 0; 1. 0] will test -1. 0; -one. 001; In practice, with the method of localization of faults, they also create tests that match the allowable values, that is, internal for the multiplier and t, that insignificantly differ from the boundary values: -1. 0; -one. 001; 0.999; - 0.999

The Structure and Principles of the WWW The WWW is made up of millions of Web servers located around the world. A web server is a program that runs on a computer connected to a network and transmits data using the HTTP protocol. To identify resources (often files or parts of them), the WWW uses URI (Uniform Resource Identifier) resource identifiers. This network uses Uniform Resource Locators (URLs) to locate resources. These URL locators are a combination of a URI and a DNS system. The domain name (or IP address) is part of the URL to identify the computer (its network interface) on which the web server program is running. On the client computer, to view the information received from the web server, use special program- web browser. The main function of a web browser is to display hypertext pages (web pages). To create hypertext pages on the WWW, HTML was originally used. A plurality of web pages form a website.

Proxy servers A proxy server is a service on computer networks that allows clients to make indirect requests to other network services. First, the client connects to the proxy server and requests some resource located on another server. The proxy server then either connects to the specified server and obtains the resource from it, or returns the resource from its own cache (if any). In some cases, the client's request or the server's response may be modified by the proxy for specific purposes. Also, the proxy server allows you to protect the client computer from some network attacks.

Application level Internet protocols The top level in the hierarchy of Internet protocols is occupied by the following application level protocols: DNS - a distributed domain name system that, upon request containing the domain name of a host, reports an IP address; HTTP - protocol for transferring hypertext to the Internet; HTTPS is an extension of the HTTP protocol that supports encryption; FTP (File Transfer Protocol - RFC 959) - a protocol designed for transferring files over computer networks; FTP allows you to connect to FTP servers, view the contents of directories, and upload files from or to a server; in addition, the mode of transferring files between servers is possible; FTP allows you to exchange files and perform operations on them over TCP networks. This protocol works independently of operating systems. Telnet (TELecommunication NETwork - RFC 854) - network protocol to implement a text interface over the network; The telnet protocol works according to the principles of a client-server architecture and provides alphanumeric terminal emulation by restricting the user to command line mode. The telnet application provided a language for terminals to communicate with remote computers. SSH (Secure Shell - RFC 4251) is an application protocol that allows remote control operating system and file transfer. Unlike Telnet, it encrypts all traffic; It is similar in functionality to the telnet and rlogin protocols, but unlike them, it encrypts all traffic, including transmitted passwords. SSH clients and SSH servers are available for most operating systems.

mail protocols. POP 3 (Post Office Protocol Version 3 - RFC 1939) is the mail client protocol used by the mail client to receive email messages from the server; IMAP (Internet Message Access Protocol - RFC 3501) is a protocol for accessing e-mail on the Internet. Similar to POP 3, but provides the user with rich options for working with mailboxes located on a central server. Emails can be manipulated from the user's (client's) computer without the need to constantly send files with the full content of letters from the server and back; SMTP (Simple Mail Transfer Protocol - RFC 2821) is a protocol that is used to send mail from users to servers and between servers for further transmission to the recipient. The mail client must use the POP 3 or IMAP protocols to receive mail; .

The HTTP protocol (Hyper. Text Transfer Protocol - RFC 1945, RFC 2616) is an application layer protocol for transferring hypertext. All software for working with the HTTP protocol is divided into three main categories: Servers - providers of information storage and processing services (request processing). Clients - end users of server services (sending requests). Proxy servers to support transport services. The main clients are browsers such as: Internet Explorer, Opera, Mozilla Firefox, Google Chrome, Safari and others. The most popular web server implementations are: Internet Information Services (IIS), Apache, lighttpd, nginx. The most famous implementations of proxy servers: Squid, User. Gate, Multiproxy, Naviscope.

HTTP session scheme Establishing a TCP connection. Client request. Server response. Termination of the TCP connection. Thus, the client sends a request to the server, receives a response from it, after which the interaction stops. Typically, a client request is a request for an HTML document or some other resource, and the server's response contains the code for that resource. The HTTP request sent from the client to the server consists of the following components. Status line (status line or query line). Header fields. Empty line. Request body. The status bar, together with the header fields, is sometimes also referred to as the request header.

Request Methods The method specified in the status bar determines how to act on the resource whose URL is given in the same row. The method can take the values GET, POST, HEAD, PUT, DELETE, etc. Despite the abundance of methods, only two of them are really important for a web programmer: GET and POST. GET - is intended to get a resource with the specified URL. Upon receiving a GET request, the server MUST read the specified resource and include the resource ID in the response to the client. The resource whose URL is passed as part of the request does not have to be an HTML page, image file, or other data. The resource URL can point to the program's executable code, which, under certain conditions, must be run on the server. In this case, the client is returned not the program code, but the data generated during its execution. Although, by definition, the GET method is for retrieving information, it can be used for other purposes as well. The GET method is fine for passing small pieces of data to the server. POST - the main purpose is to transfer data to the server. However, like the GET method, the POST method can be used in many ways and is often used to retrieve information from a server. As with the GET method, the URL given in the status bar points to a specific resource. The POST method can also be used to start a process. The HEAD and PUT methods are modifications of the GET and POST methods.

Request Header Elements (continued) The HTTP protocol version is typically specified in the following format: HTTP/version. modification The header fields following the status line allow you to refine the request, that is, to send additional information to the server. The header field has the following format: Field_name: Value The purpose of the field is determined by its name, which is separated from the value by a colon.

HTTP request header fields. Header fields HTTP request value Host Domain name or IP address of the host that the client is accessing Referer URL of the document that refers to the resource specified in the status bar From Email address of the user working with the client Accept MIME types of data processed by the client. This field can have multiple values separated by commas. Often, the Accept header field is used to tell the server what types of graphics files the client supports. Accept-Language A set of comma-separated two-character identifiers that indicate the languages supported by the client Accept-Charset Content-Type Content-Length A list of supported MIME character sets -type of data contained in the request body (if the request does not consist of one header) Number of characters contained in the request body (if the request does not consist of one header) Range Present if the client does not request the entire document, but only part of it Connection Used to manage a TCP connection. If the field contains Close, it means that after processing the request, the server should close the connection. The Keep-Alive value suggests that the TCP connection not be closed so that it can be used for subsequent requests User-Agent client information

An example of an HTML request generated by a browser GET http://oak. oakland. edu/HTTP/1. 0 Connection: Keep-Alive User-Agent: Mozilla/4. 04 (Win 95; I) Host: oakland. edu Accept: image/gif, image/x-xbitmap, image/jpeg, image/png, */* Accept-Language: en Accept-Charset: iso-8859 -l, *, utf-8 must answer him. Knowing the structure of the server response is necessary for a web application developer, since programs that run on the server must independently form a response to the client.

The server response also consists of the following four components. Status bar. Header fields. Empty line. Response body. The server's response to the client begins with a status line that has the following format: Protocol_version Response_code Explanatory_message Protocol_version is specified in the same format as in the client's request and has the same meaning. Response_Code is a three-digit decimal number that encodes the result of the request being served by the server. Explanatory_message duplicates the response code in symbolic form. This is a character string that is not processed by the client. It is intended for system administrator or an operator who maintains the system, and is the decoding of the response code.

Server response code Of the three digits that make up the response code, the first (highest) defines the response class, the remaining two are the response number within the class. For example, if the request was processed successfully, the client receives the following message: HTTP/1. 0 200 OK HTTP protocol version 1. 0 is followed by the code 200. In this code, the character 2 means the client's request was successfully processed, and the remaining two digits (00) indicate the number of this message. In currently used implementations of the HTTP protocol, the first digit cannot be greater than 5 and defines the following response classes: 1 - a special class of messages called informational. A response code starting with 1 means that the server is continuing to process the request. When exchanging data between an HTTP client and an HTTP server, messages of this class are rarely used. 2 - successful processing of the client's request. 3 - request redirection. In order for the request to be served, additional steps must be taken. 4 - client error. Typically, a response code beginning with the number 4 is returned if a syntax error has been encountered in the client's request. 5 - server error. For one reason or another, the server is unable to fulfill the request.

Server Response Code Classes Code 100 Explanation Continue Interpretation Part of the request has been accepted and the server is waiting for the client to continue the request 200 OK 201 202 Created Accepted The request was successfully processed and the data specified in the request was sent in the client's response A new resource was created as a result of processing the request The request was accepted server, but its processing has not been completed. This response code does not guarantee that the request will be processed without errors. 206 Partial Content 301 Multiple Choice 302 400 403 404 405 500 501 Moved Permanently Moved Temporarily Bad Request Forbidden Not Found Method Not Allowed Internal Server Error Not Implemented 503 505 one resource. The response body may contain instructions on how to correctly identify the requested resource The requested resource is no longer located on the server The requested resource has temporarily changed its address A syntax error was found in the client's request The resource on the server is not available for the given user The resource specified by the client is not on the server Server does not support the method specified in the request One of the server components is not functioning correctly The server's functionality is insufficient to fulfill the client's request Service Unavailable Service is temporarily unavailable HTTP Version not Supported The HTTP version specified in the request is not supported by the server

Web server response header fields. Field name Server Content description Name and version number of the server Age Time in seconds since the resource was created Allow List of methods allowed for this resource Content. Language Languages that the client must support in order to correctly display the transmitted resource Content-Type MIME type of data contained in the server response body Content-Length Number of characters contained in the server response body Last-Modified Date and time last change resource Date Date and time that determines when the response is generated. Expires Date and time that determines when information sent to the client is considered stale. Location This field specifies the actual location of the resource. It is used to redirect a request to the Cache-Control Cache Control Directive. For example, no-cache means the data should not be cached.

An example response to an HTTP/1 request. 1200 OK Server: Microsoft-IIS/5. 1X-Powered-By: ASP. NET Date: Mon, 20 OCT 2008 11:25:56 GMT Content-Type: text/html Accept-Ranges: bytes Last-Modified: Sat, 18 Oct 2008 15:05:44 GMTE Tag: "b 66 a 667 f 948 c 92: 8 a 5 "Content-Length: 426