Information technology and the Internet. Network information technologies, global computer network Internet

What is network technology? Why is it needed? What is it used for? Answers to these, as well as a number of other questions, will be given within the framework of this article.

Several important parameters

Data transfer rate. This characteristic determines how much information (measured in most cases in bits) can be transmitted through the network in a certain period of time.
Frame format. Information that is transmitted through the network is combined into information packets. They are called frames.
Signal coding type. IN in this case it is being decided how to encrypt information in electrical impulses.
Transmission medium. This designation is used for the material, as a rule, it is a cable through which the flow of information passes, which is subsequently displayed on monitor screens.
Network topology. This is a schematic construction of a structure through which information is transmitted. As a rule, a tire, a star and a ring are used.
Access method.

The set of all these parameters determines the network technology, what it is, what devices it uses and its characteristics. As you can guess, there are a great many of them.

General information

But what is network technology? After all, the definition of this concept was never given! So, network technology is a coordinated set of standard protocols and software and hardware that implement them in a volume sufficient to build a local computer network. This determines how the data transmission medium will be accessed. Alternatively, you can also find the name “ basic technologies" It is not possible to consider them all within the framework of the article due to the large number, so attention will be paid to the most popular: Ethernet, Token-Ring, ArcNet and FDDI. What are they?

Ethernet

On at the moment This is the most popular network technology around the world. If the cable fails, then the probability that it is the one being used is close to one hundred percent. Ethernet can be safely included in the best network information Technology, which is due to low cost, high speed and quality of communication. The most famous type is IEEE802.3/Ethernet. But based on it, two very interesting options. The first (IEEE802.3u/Fast Ethernet) allows for a transmission speed of 100 Mbit/second. This option has three modifications. They differ from each other in the material used for the cable, the length of the active segment and the specific scope of the transmission range. But fluctuations occur in the style of “plus or minus 100 Mbit/second”. Another option is IEEE802.3z/Gigabit Ethernet. Its transmission capacity is 1000 Mbit/s. This variation has four modifications.

Token-Ring

Network information technologies of this type are used to create a shared data transmission medium, which is ultimately formed as the union of all nodes into one ring. Under construction this technology on a star-ring topology. The first one is the main one, and the second one is the additional one. To gain access to the network, the token method is used. Maximum length rings can be 4 thousand meters, and the number of nodes can be 260 pieces. The data transfer rate does not exceed 16 Mbit/second.

ArcNet

This option uses a bus and passive star topology. Moreover, it can be built on unshielded twisted pair and fiber optic cable. ArcNet is a true old-timer in the world of networking technologies. The network length can reach 6000 meters, and the maximum number of subscribers is 255. It should be noted that the main disadvantage of this approach is its low data transfer rate, which is only 2.5 Mbit/second. But this network technology is still widely used. This is due to its high reliability, low cost of adapters and flexibility. Networks and network technologies, built according to other principles, may have higher speed indicators, but precisely because ArcNet provides high data yield, this allows us not to discount it. An important advantage this option is that the access method used is by delegation of authority.

FDDI

Network computer technology of this type are standardized architecture specifications high speed transmission data using fiber optic lines. FDDI has been significantly influenced by ArcNet and Token-Ring. Therefore, this network technology can be considered as an improved data transmission mechanism based on existing developments. The ring of this network can reach a length of one hundred kilometers. Despite the considerable distance, the maximum number of subscribers who can connect to it is only 500 nodes. It should be noted that FDDI is considered highly reliable due to the presence of the main and backup paths data transfer. Adding to its popularity is the ability to quickly transfer data - approximately 100 Mbit/second.

Technical aspect

Having considered what the basics of network technologies are and what they are used, now let’s pay attention to how everything works. Initially, it should be noted that the previously discussed options are exclusively local means electronic connections computers. But there are also global networks. There are about two hundred of them in the world. How do modern network technologies work? To do this, let's look at the current construction principle. So, there are computers that are united into one network. Conventionally, they are divided into subscriber (main) and auxiliary. The former are engaged in all information and computing work. What the network resources will be depends on them. Auxiliary ones are engaged in the transformation of information and its transmission through communication channels. Due to the fact that they have to process a significant amount of data, servers boast increased power. But the final recipient of any information is still ordinary host computers, which are most often represented by personal computers. Network information technologies can use the following types of servers:

Network. Engaged in the transfer of information.
Terminal. Ensures the functioning of a multi-user system.
Databases. Involved in processing database queries in multi-user systems.

Circuit Switching Networks

They are created thanks to physical connection clients for the time when messages will be transmitted. What does this look like in practice? In such cases, a direct connection is created to send and receive information from point A to point B. It includes the channels of one of many (usually) message delivery options. And the created connection for successful transfer must remain unchanged throughout the session. But in this case, quite strong disadvantages appear. So, you have to wait a relatively long time for a connection. This is accompanied by high data transmission costs and low channel utilization. Therefore, the use of network technologies of this type is not common.

Message Switching Networks

In this case, all information is transmitted in small portions. Direct connection in such cases it is not established. Data transmission is carried out over the first free available channel. And so on until the message is transmitted to its recipient. At the same time, servers are constantly engaged in receiving information, collecting it, checking it and establishing a route. And then the message is passed on. Among the advantages, it is necessary to note the low cost of transmission. But in this case, there are still problems such as low speed and the impossibility of dialogue between computers in real time.

Packet switching networks

This is the most advanced and popular method today. The development of network technologies has led to the fact that information is now exchanged through short information packets of a fixed structure. What are they? Packets are parts of messages that meet a certain standard. Their short length helps prevent network blocking. Thanks to this, the queue at the switching nodes is reduced. Implemented fast connection, low error rates are maintained, and significant gains have been made in terms of increasing network reliability and efficiency. It should also be noted that there are different configurations of this approach to construction. So, if a network provides switching of messages, packets and channels, then it is called integral, that is, it can be decomposed. Some of the resources can be used exclusively. Thus, some channels can be used to transmit direct messages. They are created for the duration of data transfer between different networks. When the session for sending information ends, they break up into independent trunk channels. When using packet technology, it is important to configure and coordinate a large number of clients, communication lines, servers and a number of other devices. Establishing rules known as protocols helps with this. They are part of the network operating system used and are implemented at the hardware and software levels.

Abstract on the topic:

"Network information technologies"

The work was completed by:

Ivanova Alena

Krutin Rodion

Network information technologies

In the 1960s the first computer networks(VS) with a computer. Since that time, network information technologies have actually appeared, making it possible to combine technologies for collecting, storing, transmitting and processing information on a computer with communication technology.

Network is an interacting set of objects connected to each other by communication lines.

IN information processes, systems and technologies, the term “network” means at least several computers and other computers connected to each other using special equipment to provide calculations and exchange various types information. Complex networks imply large number users, a branched structure, switching and communication nodes connecting everyone into a single structure.

The basis of network technologies is computer networks– means of communication (telecommunications), with the help of which computers distributed in space are combined into a system.

Almost immediately with the advent of computer networks, they began to be used for the exchange of various kinds of data (data networks) and information. The development of computer networks and network technologies has shown the possibility of using them to organize large-scale information support for people.

This led to the fact that computer networks providing the exchange of information resources began to be called “ information networks ”, representing a type of communication networks.

Depending on the accepted control method networks are divided into: centralized, decentralized and mixed.

The Internet is a decentralized internet. The principle of its construction is to organize highways (high-speed telephone, radio, satellite and other communication lines) between central hub stations.

The growth of information systems that interconnect to exchange information and solve other problems initiated the creation international networks, and then the Internet. This contributed to the emergence of Internet technologies.

Modern network technologies provide the ability to work in deferred (offline) and interactive (online) modes, provide communication with any available information sources, allow for professionally oriented consulting and training, etc.

Online technologies include interactive types of services on the Internet: ISQ, Internet telephony, etc.

Offline technologies include: mailing lists, newsgroups, web forums, email, etc.

Internet services

There are a number of ways to work with a computer network:

receiving information from an electronic bulletin board;
exchange of data by email;
receiving mailing lists;
participation in electronic forums, teleconferences, etc.;
exchange text messages in chats;
copying files from using FTP;
use of Internet telephony, etc.

These methods constitute Internet services that are provided by network providers. Let's take a closer look at them.

1) Electronic bulletin board (eng. “Bulletin Board System”, BBS ). This is usually the name for small dial-up systems intended for local users. Modern BBSs are rarely found and used. Abroad, BBS are used, among other things, to disseminate information about organizations, local events, literature published by publishers (book reviews), etc.

2) Email
Exchange of electronic correspondence is one of the simplest but most intensively used services. In e-mail, the transport service deals with files processed by computers rather than paper transmitted through various physical means, as is done in classic mail systems. In this service, you can send files as attachments (Attachment) and send mail simultaneously to several addresses (circular). With that said, email (E-Mail) is a service postal service, in which message delivery is carried out electronic methods using computers connected to telecommunications.

3) Mailing lists
There is a form of information exchange between Internet users - “ mailing lists” (Mailing list, Listserv), reminiscent electronic conference. This is a centralized system, usually maintained by a specific initiator. He usually does it by email free newsletter information entering the conference on a specific topic. To regularly receive information, you need to subscribe to it - send a message to the mailing site.

4) Electronic conferences and forums
Electronic conference held on the Internet is similar to automatically maintained mailing lists emails on certain topics. As part of the conference topic, the subscriber writes a letter, sends it to a specific address, and the letter is automatically sent to everyone who has subscribed to this conference (its participants). The main difference from mailing lists is that messages are not sent to a specific user, but are stored on many servers specially organized to support the relevant conferences. Messages are deleted after some time. Such conferences exist as long as there are people who write in them.

Forums form communities of people on the Internet (user groups global network) for exchanging opinions, consulting, receiving news by interest. To participate in them you need to fill out information message about your site and send it to the appropriate conference. Then you should answer all the questions proposed by the forum and “settle” in one or more of its conferences.

5) Chat There is a service on the Internet that allows you to organize a “conversation” between two or more users in real mode time, which is called “Chat” (English: “Chat” - talk, chat), and the service - teleconferencing in real time(IRC - Internet Relay Chat). The service is similar to teleconferencing, but is carried out in real time. Users communicate interactively with each other using keyboard text input in a special program window. This is a kind of conversation between people in writing over the Internet.

6) ICQ Type of chat - ICQ(I Seek You - I'm looking for you) application used for interactive communication between two Internet users, automatically makes a call and shows which of your friends is in touch. Each participant has his own identification number.

7) Teleconference A type of electronic conference is teleconference, i.e. conference visible from a distance (video conference) is a means and method of visual interactive communication between geographically distant people on computer networks. AT&T pioneered videoconferencing in the mid-1960s. There are three options for video conferencing: studio, group and personal.

In video conferencing, users are provided with dedicated access to group information for joint electronic thematic conferences. At the same time, each participant sees and hears the others.

Audio conferences (voice conferencing) provide users on the Internet with a call, connection and conversation similar to that carried out in a regular telephone communication. To maintain routine telephone conversations Internet telephony technology is used via the Internet.

Webcasting provides broadcast via the Internet video material of television quality image and sound. It is used when broadcasting to a large audience (more than 30 people). The difference from video conferencing is the one-way transmission of streaming images and sound. Question and answer sessions may be used.

8) Copying files from FTP Copying files on the network is done using FTP. There are special file libraries on the Internet that provide users with the opportunity to rewrite them into own computers. FTP allows you to transfer files regardless of the computers used on the network. Network users can write their files to the FTP server. To do this, they must have an FTP client program on their computers. FTP server – large storage(archive) files. The principle of its operation differs from Web servers in the structure and method of presenting information.

Hypertexts are texts with hyperlinks to other hypertexts posted on the Internet or local network COMPUTER.

To record hypertexts, the hypertext markup language HTML is used, which is understood by all browsers on all personal computers.

The HTML language is an international standard, so all hypertexts are perceived and displayed in the same way on all personal computers around the world.

To prepare hypertexts, visual hypertext editors are usually used, in which you can immediately see what the hypertext will look like on a computer and it is possible to insert hyperlinks to sites on the Internet.

One of the best visual hypertext editors is the free office editor Writer in the free office suite Open Office.

Interactive sites and programs

Interactive sites- these are sites that use interactive hypertext subroutines that allow dialogue with computer users connected to the computer network.

Hypertext routines are included in hypertexts along with hypertext forms and subroutines called scripts.

To write hypertext subroutines (hypertext scripts), the JavaScript language is often used, which is an extension of the hypertext markup language HTML.

JavaScript language is an extension of HTML hypertext markup and for these reasons the JavaScript language interpreter is built into all browsers and all hypertext editors.

The JavaScript language is international standard. For this reason, interactive programs on JavaScript are executed in the same way on all computers in the world.

More than 60% of programs in the world written in the hypertext script language JavaScript.

JavaScript programs can not only be executed on any computer connected to the Internet, but their source texts can also be read on the Internet.

JavaScript programs are the best example of Open Source on the Internet - they can be read, executed, and modified by anyone familiar with the JavaScript programming language.

Modern Internet technologies

Modern Internet technologies:

web server
hypertexts and websites;
e-mail;
forums and blogs;
chat and ICQ;
tele- and videoconferences;
wiki encyclopedias;

Internet technologies in computer science

Internet technologies in computer science - various kinds of workshops on creating websites, blogs, electronic libraries and encyclopedias on the Internet.

Internet sites are sets of hypertexts with hyperlinks located on servers and portals on the Internet computer network.

Blogs on the Internet are Internet sites combined with interactive forums for communication and publication of messages and comments by site visitors.

Creating websites on the Internet is one of the most important tasks of computer science courses in universities and schools by students and schoolchildren.

Electronic libraries and encyclopedias are latest technologies publication of scientific and educational literature on the Internet.

Creating hypertext programs in JavaScript is one of the best examples teaching programming, since these programs can be published and tested on the Internet.

The following JavaScript programs were written and published on the Internet and are still workable and accessible for imitation and development new Internet textbooks.

JavaScript language is one of the best languages Internet programming training.

Interactive Internet textbooks

Interactive textbooks- these are interactive sites and programs that can conduct a dialogue with users personal computers using interactive sites and programs.

Examples interactive Internet textbooks:

Section 1. Introduction to computer science:

Interactive questions:

- Higher Attestation Commission, prof., doctor of computer sciences 05:23, July 26, 2009 (UTC)

Distance learning in computer science and ICT

Preparation of students, teachers and lecturers for the Unified State Exam in computer science can be carried out remotely using the Internet and basic teaching aids in computer science and ICT.

Distance learning like any other distance learning, it is carried out using textbooks and teaching aids, as well as passing tests and exams and course projects and papers.

Distance preparation for the Unified State Exam can be carried out not only in computer science and ICT, but also in other school general education subjects. For example - social studies.

Preparing students, teachers and computer science teachers for the Unified State Exam begins with confirming their knowledge of computer science textbooks and Unified State Exam standards.

Completion of preparation for the Unified State Exam - completion of course projects and work on computer science and ICT on the Internet computer network.

Examples of Internet course projects

Course Internet projects- these are interactive information sites with implementation coursework and tasks on solving problems in computer science, working with office packages and creating personal or school websites.

Coursework and course projects for computer science teachers and students of ITO MPGU: