Computer and telecommunication networks. Computer networks and telecommunications Computer networks Internet and telecommunications

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1 Computer networks and telecommunications. Lecture 1 1 INTRODUCTION The academic discipline "Computer networks and telecommunications" is a special one that provides basic knowledge for mastering general professional and special disciplines of the specialty Computing machines, complexes, systems and networks. The subject of the discipline is theoretical and practical foundations in the field of computer networks and telecommunications. The discipline "Computer networks and telecommunications" is based on the materials of the previously studied disciplines: "Information technology", "Electronic engineering", "Digital circuitry", "Mathematical and logical foundations of electronic computing"; has interdisciplinary connections with the disciplines "Operating systems and environments", "Design, production and operation of computer technology", "Metrology, standardization and certification". The purpose of studying the discipline "Computer networks and telecommunications" is to provide students with systematized information about the principles of organizing computer networks for various purposes, about the methods of design and operation. At the very beginning of the study of the discipline "Computer networks and telecommunications" students must learn the concept of a computer network, its purpose and advantages in comparison with autonomous computers. In the process of studying the discipline, students master the basic principles of building a network; selection of communication equipment, means of transmission, access methods; exploitation. The logical structure of the course with highlighting the main thematic sections is presented in the table. Section number Section title Lecture number 1 Basic concepts of computer networks 1 2 Local computer networks 2 3 Global computer networks 3 4 Packet transmission and exchange control methods 4 5 Methods and media of data transmission OSI reference model, standardization problems and protocols 7 7 Means of building unified networks Basic technologies of local networks 10-12

2 Computer networks and telecommunications. Lecture 1 2 As can be seen from the structure, the study of the course is based on the sequential study of eight thematic sections. Each section includes one or more lectures. In accordance with the logical structure of the course, we will proceed to the study of the first section and the first lecture. THEME OF LECTURE 1: "BASIC CONCEPTS OF COMPUTER NETWORKS" The objectives of the lecture are: to study the basic concepts of computer networks and telecommunications; consider the advantages and disadvantages of computer networks in comparison with stand-alone computers; study various classifications of computer networks. Lecture plan: 1. Definition and purpose of a computer network 2. Advantages and disadvantages of computer networks 3. Classification of computer networks 4. Multilayer model 1. Definition and purpose of a computer network The first computer networks appeared in the 60s of the last century. The purpose of their creation is to combine technologies for collecting, storing, processing and transmitting information with communication technology. Thus, the development of computer telecommunications began long before the Internet (in its present form) and long before the advent of Windows. For example, in the 1980s, publicly available BBS (Electronic Bulletin Board) file servers appeared around the world, running in an MS-DOS environment. BBS subscribers got the opportunity to view and post announcements for free, exchange mail messages and files, participate in discussions (forums), etc. Computer networks have become a logical result of the evolution of computer and telecommunication technologies. By combining computers into a network, the efficiency of data processing is significantly increased. there is no need for intermediate data carriers and the efficiency of interaction with computers increases. Currently, personal computers are practically not used in stand-alone mode; they, as a rule, are united into computer or computer networks.

3 Computer networks and telecommunications. Lecture 1 3 A computer network is a collection of computers and various devices that provide information exchange between computers in a network connected by communication lines. There are many examples when the integration of computers into a network is simply necessary: \u200b\u200bthe sale of air and railway tickets; banking network; computer Club. There are other possible names for a computer network: computer telecommunications network, computer computer network. The main purpose of computer networks is to provide access to distributed resources. Let's consider a few more definitions related to the concept of a computer network. Telecommunication in the broad sense of the word is communication between subjects (people, devices, computers) located at such a distance from each other that it excludes direct contact ("tele" remote, "communication" communication, communication). Example. Telecommunications in the broad sense of the word: exchange of light signals at sea between ships; telephone; telegraph; the television. Examples of word usage: telecommunications in large cities; telecommunication equipment; telecommunication services. A computer telecommunication network is a network of exchange and distributed information processing formed by a multitude of interconnected subscriber systems and communication means; the means of transmission and processing of information are focused on the collective use of common network resources of hardware, information, software. Example. Network printer, information database, OS. A subscriber system is a set of computers, software, peripheral equipment, communication facilities that perform applied processes. Telecommunication networks include: 1. Computer networks (for data transmission)

4 Computer networks and telecommunications. Lecture Telephone networks (transmission of voice information) 3. Radio networks (transmission of voice information - broadcast services) 4. Television networks (transmission of voice and image - broadcast services) 2. Advantages and disadvantages of computer networks Consider the advantages and disadvantages of computer networks in comparison with autonomous computers. Networking computers has many benefits. Among them are the following: joint use of all types of resources: hardware, software, information; saving material resources when sharing resources; providing distributed data processing and parallel processing by many computers; the possibility of exchanging large amounts of information between computers, remote from each other at considerable distances; providing a wider range of services, including such as e-mail, newsgroups, electronic bulletin boards, online shopping, forums, distance learning and much more; There are other advantages of computer networks: facilitation of work on the improvement of technical, software and information resources; relative independence in the territorial distribution of computers; prompt and high-quality decision making. Disadvantages of a computer network: the possibility of spreading computer viruses; the possibility of unauthorized access to information; when using the resources of global networks (for example, the Internet), the possibility of obtaining inaccurate or outdated information. 3. Classifications of computer networks There are various classifications of computer networks. Let's consider some of them, highlighting the classification feature and types of networks. Classification 1 depending on the distance between the network nodes (by the size of the territory. On this basis, there are three types of networks: LAN, GVS, RVS.

5 Computer networks and telecommunications. Lecture 1 5 Local area network (LAN) (LAN Local Area Network) connects subscriber systems located within a small area. Comment. It should be noted that a small area in this definition is a very relative concept. The length of a LAN can be limited to both a few kilometers and tens of thousands of kilometers. The class of local networks includes networks of enterprises, firms, banks, offices, educational institutions, etc. In general, a LAN is a communication system that belongs to one organization. The WAN Wide Area Network connects subscriber systems dispersed over a large area, covering various countries and continents. Global networks solve the problem of combining information resources of all mankind and organizing access to them. The interaction of AC is carried out on the basis of various territorial communication networks, which use telephone communication lines, radio communication, and satellite communication systems. An example of a global network is the Internet. A regional computer network (RNS), or a network of megalopolises (MAN Metropolitan Area Network), unites subscriber systems located at a considerable distance from each other: within a separate country, region, or a big city. Comment. Regional computer networks within a city are often called urban. RVS are limited to a certain administrative unit. The length of the RVS is different: from tens of kilometers to hundreds of thousands of kilometers. RVS communication channels wireless and wire lines. While local area networks are best suited for sharing resources over short distances and broadcasts, and wide area networks provide long-distance operation, but with limited speed and rich set of services, metropolitan networks occupy some intermediate position. An interesting example of the connection between local and global networks is a virtual private network (VPN).

6 Computer networks and telecommunications. Lecture 1 6 This is the name of an organization's network, resulting from the combination of two or more geographically separated LANs using public channels of global networks, for example, via the Internet. The combination of global, regional and local computer networks allows you to create multi-level hierarchies that provide powerful tools for processing huge amounts of data and access to almost unlimited information resources. Local area networks (LANs) can be included as components of a regional network; regional networks to unite in a global network; finally, global networks can form even larger structures. The largest amalgamation of computer networks on the scale of the planet Earth today is the "network of networks" Internet. Classification 2 by the way of management. On this basis, the following types are distinguished: networks with centralized control (dedicated server); with decentralized management (peer-to-peer network); with mixed control. A centrally controlled network (multilevel or hierarchical) is a network with a dedicated server. In such a network, one of the computers performs the functions of network management: storing data intended for use by all workstations; management of interaction between workstations; other service functions (administration, management of hardware devices, etc.). A peer-to-peer network (peer-to-peer, or decentralized network) is a network in which all computers are equal. Classification 3 according to the organization of information transfer. Information selection networks: are built on the basis of a mono-channel (a single communication channel that unites all computers in the network). The interaction of subscribers is carried out by the selection (selection) of data blocks (frames) addressed to them: all network subscribers have access to all frames transmitted in the network, but a copy of the frame is taken only by the subscriber systems for which they are intended. Information-routing networks: These networks can use multiple routes to transfer frames from source to destination. Therefore with

7 Computer networks and telecommunications. Lecture 1 7 using communication systems of the network, the problem of choosing the optimal route is solved. Classification 4 by access method. Competitive: the subscriber starts data transmission if he finds a free line, or postpones the transmission for a certain period of time if the network is busy with another subscriber. Deterministic: time reservation for each subscriber has a certain period during which the line belongs only to him. Classification 5 according to the type of data transmission organization. This classification is specific to information routing networks. By the type of organization of data transmission, the following types of networks are distinguished: 1. With switching of circuits (channels). 2.Switching messages. 3. Networks of information packet switching. Circuit switching networks are historically earlier. Circuit switching implies the formation of an end-to-end communication channel for direct data transfer between nodes before the start of information transfer. Separate channels are interconnected by special equipment by switches that can establish connections between any end nodes of the network. Before transferring data, it is always necessary to perform the connection establishment procedure, during which the composite channel is created. The ease of this method implies a number of disadvantages, and the most important is the low utilization of channels (they must be turned on at the same time, therefore, there is an increase in the waiting time of other clients). Example of a circuit-switched network: transferring information by telephone. In a message switching network, information is transmitted in chunks called messages. Data transfer is carried out immediately after the release of the very first of the required channels. With this switching method, the message is transmitted through several transit computers, where it is completely buffered on disk (stored in memory). The transit node cannot initiate further transmission of a portion of the message if it is still being received. A message, unlike a packet, has an arbitrary length. Each server performs the following operations: receiving information, assembling it, checking, routing, sending a message. Example: email, newsgroups;

8 Computer networks and telecommunications. Lecture 1 8 In the information packet switching network, data transmission is carried out in short packets of fixed length (before the transmission starts, the message is split into packets). Each packet is supplied with protocol information (packet start and end codes, sender and recipient addresses, packet number in the message, information for checking the reliability of transmitted data at intermediate communication nodes and at the destination). An end-to-end channel between the sender and the receiver is not established until the transfer of information begins. Information packet (IP) part of a message that satisfies a certain standard (a packet that necessarily contains a data field). Advantages of data packet switching: short packet length prevents blocking of the communication line and does not allow queues to grow in switching nodes, hence fast connection, low error rate, reliability and efficiency of network use. Disadvantages of switching information packets: routing problems (they are solved not only by software, but also by hardware). Fixed routing assumes the presence of route tables to which routes from one client to another are assigned. This provides a fairly straightforward implementation, but network load can be uneven. The method of the shortest queue is applied here. The essence of the method: each channel has a priority, which is determined in accordance with the inverse proportionality of the length. Data transmission is carried out on the first free channel with the highest priority. Thus, the use of this method assumes a minimum MT delay. Example: information transfer in a local Ethernet network (Fast Ethernet, Gigabit Ethernet). Comment. In practice, there are also integrated networks (combination of commutations). Classification 6 according to program compatibility: homogeneous or homogeneous (these are CWs that combine software-compatible computers); heterogeneous or heterogeneous (these are KS that unite software incompatible computers). Classification 7 by topology:

9 Computer networks and telecommunications. Lecture 1 9 broadcast (shared bus, passive tree, passive star). In broadcasting configurations, at any given time, only one RS can operate to transmit a frame, the other RSs can receive this frame (networks with information selection); consecutive (arbitrary or cellular, ring, active star, active tree, fully connected). In sequential configurations typical for networks with information routing, data transmission is carried out sequentially from one PC to a neighboring one; Classification 8 according to the scale of the production unit. department networks are used by a small group of employees working in one department of the enterprise; networks of campuses networks of enterprises, organizations ("campus" campus) unite networks of departments within a single building or one territory; corporate networks are enterprise-wide networks that unite a large number of computers in all areas of the enterprise. Classification 9 by purpose. informational (information retrieval); managers (technological, administrative, organizational and other processes); calculated; processing documentary information, etc. Classification 10 by the type of data transmission medium: Wired; Wireless. Wired: coaxial, twisted pair, fiber optic. Wireless: with the transmission of information over radio channels with the transmission of information in the infrared range. Classification 11 by data transmission rate: low-speed medium-speed high-speed Example. Low speed:

10 Computer networks and telecommunications. Lecture 1 10 Token-Ring ArcNet Medium-speed: Ethernet High-speed: Fast Ethernet, Gigabit Ethernet, 10 Gigabit Ethernet 4. Multilayer model Thus, a computer network is a complex complex of interconnected and consistently functioning software and hardware components. The study of the network as a whole assumes knowledge of the principles of operation of its individual elements, such as: computers; communication equipment; OS; network applications. The whole complex of software and hardware means of a network can be described by a multilayer model. At the heart of any network is the hardware layer of standardized computing platforms. Computers of various classes are successfully used in networks - from personal computers to mainframes and super-computers. The set of computers in the network must correspond to the set of tasks solved by the network. The second layer is communication equipment. While computers are central to data processing in networks, communication devices play an equally important role. Cabling systems, repeaters, bridges, switches, routers and modular hubs have gone from being ancillary network components to being mainstream alongside computers and system software, both in terms of impact on network performance and cost. Today, a communication device can be a complex specialized multiprocessor that needs to be configured, optimized and administered.

11 Computer networks and telecommunications. Lecture 1 11 The third layer, which forms the network software platform, are operating systems (OS). The efficiency of the entire network depends on which concepts of management of local and distributed resources are used as the basis of the network operating system. When designing a network, it is important to consider how easily a given operating system can interact with other network operating systems, what level of security and data protection it provides, to what extent it can increase the number of users, whether it can be transferred to a different type of computer, and many other considerations. The topmost layer of network tools is formed by various network applications such as network databases, mail systems, data archiving tools, team automation systems, etc. It is very important to be aware of the range of capabilities that applications provide for different areas of application, and also to know how they are compatible with other network applications and operating systems.

12 Computer networks and telecommunications. Lecture 1 12 So, in lecture 1 we considered the basic concepts of computer networks and telecommunications, the advantages and disadvantages of computer networks, various classifications of networks. To control and assess the knowledge gained on the topic "Basic concepts of computer networks", you are invited to complete the test, which you can find on the website. You can find additional information on the studied topic in the literature. List of recommended literature 1. Broido VL, Ilyina OP Computing systems, networks and telecommunications: Textbook for universities. 4th ed. - SPb .: PETER, Melekhin, V.F. Computing machines, systems and networks: textbook / V.F. Melekhin, E.G. Pavlovsky. - 2nd ed., Erased. - M .: Academy, Olifer V. G., Olifer N. A. Computer networks. Principles, technologies, protocols: Textbook for universities. 4th ed. - SPb .: PETER, Peskova, S.A. Networks and telecommunications: textbook. manual / S.A. Peskova, A.V. Kuzin, A.N. Volkov. - 2nd ed., Erased. - M .: Academy, Tanenbaum E. S. Computer networks. 4th ed. - SPb .: PETER, 2011.

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Topic 4 “Computer networks, network and telecommunication technologies. The Internet"

A computer network is an association of individual PCs, which makes it possible to share information and technical resources. Using the network, you can view any information in any of the connected PCs

Information resources are files of programs and documents, technical resources are a printer, modem, disks. For the network to function, special hardware and technical support is required.

Until recently, two types of networks were distinguished: local and global ... Now they add the 3rd kind here - regional or corporate .

Local networks

Local networks are a small group of PCs located in the same building or adjacent buildings and interconnected by communication lines (wires) of relatively short length. When connecting 2 PCs (local cable connection), no additional hardware or network setup is required. But if there are more than 2 PCs, then there is a need for special settings for computer control and, even, additional equipment may appear - a network adapter. A network adapter or HUB is a device that allows multiple PCs to operate on a network, which determines the order in which data is transmitted over communication lines. In this case, the PC must also have a network card or network card. The way a PC is connected to a local network (network configuration) is called a network topology.

There are several types of topology:

The combined method is a combination of any three in any sequence.

It can be clearly seen from the figures that only the star connection has a network adapter. The advantage of the 1st and 2nd connections is a higher signal transmission speed over the network, but if one of the PCs fails, the operation of the entire network is disrupted. In a "star" PC breakdown does not affect the network, but the network speed is slightly lower.

The topology is selected based on the needs of the enterprise. If the enterprise occupies a multi-storey building or several neighboring buildings, then it is more expedient to use a combined scheme. And the composition of the hardware and software depends on the selected topology.

In addition, there are 2 types of networks: server-client and peer-to-peer .

In the first case, one PC is a control or server. Usually it has more memory, various office equipment devices are connected to it: printers, modem; it stores information common to all and does most of the work. The rest of the PCs are called stations. If there is no server, and all PCs have equal opportunities, then such a network is called a peer-to-peer network. To work in such a network, it is enough to set up "Network Neighborhood", assign unique numbers to all PCs and one name for the group. When creating working groups, the belonging of a PC to a particular department is taken into account: accounting, administration, personnel department, etc. In the future, the user just needs to enter the "Network Neighborhood", select the PC by name, double-click on the desired icon, enter the password if it is provided and it appears on someone else's PC. In this case, “Access” must be configured on all PCs in the properties of the C: drive or another folder. There are 2 types of access:

full, when all users are allowed to view the contents of folders, read files, make and save changes, delete, rename, etc.

read only, i.e. other users can view and read any files, copy them to their PC, but they are not allowed to make any changes.

Global networks.

Global networks connect PCs located in different areas, cities and even countries. They use telephone lines and modems. One of the most widespread networks is the Internet. There are other global networks in the world. Some of them are free, just like the Internet, others are commercial. The Internet provides users with several types of services: searching for the information they need, forwarding mail, entertainment, news, and much more. Internet connection nowadays can also be very different.

Regional or corporate networks.

These networks, like the previous ones, use a modem and telephone lines, but they may not have access to the Internet, just as it is not always possible to get into the network to them, but only to a narrow circle belonging to one corporation or region. An example of such networks is the internal network of KSU, the network of any bank, the network of the city education department of Kostanay. Such networks, as a rule, represent a connection to a global network, to which only some PCs have access, and several dozen local networks that have access to the Internet only through server computers.

Network designation:

Wide Area Networks (WAN);

Regional networks (MAN - Metropolitan Area Network);

Local area networks (LAN - Local Area Network).

Speed transmission data over a communication channel is measured by the number of bits of information transmitted per unit of time - a second.

Remember! The unit of measurement for the data transfer rate is bits per second.

Note. A commonly used unit of measure for speed is baud. Baud is the number of changes in the state of the transmission medium per second. Since each change of state can correspond to several bits of data, the actual rate in bits per second can exceed the baud rate.

The data transfer rate depends on the type and quality of the communication channel, the type of modems used and the adopted synchronization method.

Tasks.

1. Theoretically, a modem transmitting information at a speed of 57600 bps can transmit 2 pages of text (3600 bytes) during:

C) 0.5 s;

D) 3 min 26 s;

E) 2 min 16 sec.

2. Determine the transmission time of two pages of text (3 600 bytes) by the modem transmitting information at a speed of 28 800 bps.

A) 1 minute;

C) 1 second;

E) 2 minutes.

the Internet

The global Internet network emerged in the early 60s. Nowadays, practically all known communication lines are used on the Internet: from low-speed telephone lines to high-speed satellite channels. Hardware and software are also different. Access to information in telecommunication networks is carried out through special protocols, programs, server computers. These components are called network services, as well as services, resources, or services.

In order for information to be transferred between computers, regardless of the communication lines used, such as computers and software, special information transfer protocols have been developed. They work on the principle of breaking data into blocks of a certain size (packets), which are sequentially sent to the addressee.

There are two main protocols used on the Internet:

Internet Protocol (IP) divides the transmitted data into individual packets and provides a header indicating the recipient's address.

The Transmission Control Protocol (TCP) is responsible for the correct delivery of such a packet, i.e. splitting files into IP packets during transmission and assembling files during receiving;

Since both of these protocols are a single whole, they speak of the TCP / IP protocol. This protocol is a kind of language, without which mutual understanding of individual participants is impossible - various programs, computers and networks included in the global network.

The Internet is completely decentralized. This means there is no governing body that dictates the terms and conditions of the network, monitors compliance and punishes violators. Over time, certain generally accepted principles of network operation have developed.

Individual computers and their users are identified using two addresses:

A domain address that is understandable to humans;

An IP address that the computer understands.

Example:
address www.gelcom.ru:

Www - resource name - World Wide Web;

Relcom - company name:

Ru - Russia.

An IP address is a 32-bit number (eg _49._19._81._ _2), divided by dots into 4 parts, none of which can exceed 255. This address does not tell the user much, but it is it that is read by the computer.

To see the IP address of your PC, you need to open the properties of the "Network Neighborhood" service through the right mouse button, then also through the right button open the properties of your network connection and look at the properties of "Internet Protocol ТСР / IP". There are two types of IP addresses: static and dynamic. The static address is permanently assigned to the PC and registered in the properties window, while the dynamic address is not explicitly indicated, since each time it connects to the Internet, the PC receives a free (not occupied) IP address from the server. World Wide Web. The emergence and development of the global information network Internet led to the development of special programs - browsers. These programs organize viewing of Internet resources and are focused on working in networks implemented according to the Internet standards and the World Wide Web - WWW.

The World Wide Web (WWW) is one of the technologies of the Internet. The essence of the WWW is to present information in the form of separate text, graphic and other files located on different computers. These files are linked together by hyperlinks. The collection of such files is called a Web document or Web site. A website is made up of individual web pages. Several Web documents are hosted on a Web server. A Web document is searched for and accessed at a special URL (Uniform Resource Locator). A standard URL consists of three parts, which define the information transfer protocol, the name of the computer on which the information is located, and the path to it. For example, the URL structure for toys selling company Vermont Teddy Bears looks like this:

By specifying the URL, the user uniquely identifies the required file.

In order for information to be quickly and efficiently transmitted over networks, special file formats are used, designed specifically for working on the Internet and the WWW:

Special software is required to view Web documents. Such programs - applications are called Web browsers.

The most popular are:

Internet Explog (developed by Microsoft)

Netscape Navigator (by Netscape Communications Cor.).

Opera and many others.

In addition to the WWW resource, Web browsers allow access to other Internet resources:

search engines,

email,

• fTP file archives,

  teleconferences.

Email (e-mail) (a trademark of Electronic Mai) was registered in 1974. Until then, the name Computer Based Messaging System was used.

Email by its principle it is very similar to the usual one, it is simply not physical letters that are sent, but their informational images, i.e. electronic documents. This both imposes a number of restrictions and provides a number of advantages. The main advantage is efficiency: usually mail arrives in a few minutes. Electronic signature does not use geographic addresses, and mailboxes are not tied to any geographic location. Mailboxes are located on server computers called mail servers. The EDS service works on the "client-server" principle. When creating a letter on his PC, the user sends it from his mailbox on his server to someone else's mailbox, which can be located on the same server or on another. The letter is stored on the server in the mailbox. The user, having entered his mailbox, can read the letter, delete it like a regular file, send a reply, i.e. create a new file. In fact, at the same time he works on the server, uses the server resources. Files of pictures, audio or video are attached to letters using a special command.

To achieve confidentiality, when creating his mailbox, each user comes up with a username, which is also called "nickname" and password. The mail server assumes guarantees to keep them confidential. The user can check his mailbox from any city, from any PC with Internet access.

The email address looks like this:

login @ mail server name

For example: [email protected]

If a letter cannot be delivered immediately, for example, the server where the mailbox is located does not work, the letter is put on the queue and will be sent every 10-15 minutes. If, after a few hours, the letter is still not sent, then the sender is notified that the address does not exist. The postal service is designed in such a way that a letter cannot just disappear. When sending mail, interaction occurs over the outgoing mail protocol SMTP (Simple Mail Transfer Protocol - the simplest outgoing mail protocol). When receiving, the incoming mail protocol works POP3.

There are many different email programs:

Microsoft Outlook Express,

Microsoft Internet Mail,

These programs allow you to store all sent and received correspondence on your PC, and not on the mail server. This allows you to work with mail without connecting to the Internet, since the connection in this case is needed only at the time of sending and receiving mail. Each zip has at least 4 folders (directories): received, sent, drafts and trash. But usually you can create additional folders to organize your letters. But if the mailbox is on the server, that is, there is a limitation on the size of the mailbox (in Kbytes), and if you use the mail program, then the letters are, as it were, downloaded from the server and stored on the user's PC, so the volume for their storage is not limited.

Service ICQ .

Designed for communication purposes. This is a kind of Internet pager that immediately informs which of the friends is currently on the Internet and at the same time wants to communicate. Each subscriber is assigned a unique UIN - the universal Internet, which is supplied with a password. The main form of communication in ICQ is the exchange of short (up to 450 characters) messages in almost real time. You just need to install a special program on your PC, which is usually free.

Chat .

Translated from English means "friendly conversation, conversation, chatter." In the modern Internet, this term has stuck with the meaning of "real-time communication". A special IRC program - Internet Relay Chat - organizes a multi-user communication system. Nowadays, Chat is organized on many sites to attract additional users.

Forums.

They are organized on various sites to determine public opinion on a variety of issues or to exchange opinions.

Conferences.

Not only chat is used, but a webcam and microphone. It requires the use of a large number of Internet resources and high-speed communication lines so that there is no delay, i.e. to ensure synchronization of sound and picture.

Control questions

What is information?

What sections are included in computer science?

How can information be classified?

How is information measured?

Literature

1. Avetisyan RD, Avetisyan DD, Theoretical Foundations of Informatics - M .: Nauka, 1997., p. 3 - 75

2. Aladiev V.Z. and other Fundamentals of Informatics. - M .: Filin, 1999., p. 3-41

3. Makarova NV, Matveev LA, Broydo VL et al. Informatics / Ed. Makarova N.V. M, 2003.

4. Informatics / Ed. S. V. Simonovich. - SPb., 2004.

5. Moiseev A.V. Informatics. - M .: Academy, 1998.

Ontopsychology has developed a whole series of rules, recommendations for the formation of the personality of a manager, businessman, top-level leader, which are already subject to almost any leader who is able to realize their usefulness and necessity. From the entire set of these recommendations, it is advisable to single out and summarize the following:

1. No need to destroy your image by dishonest acts, fraud.

2. Do not underestimate a business partner, consider him more stupid than yourself, try to deceive him and offer a low-level market system.

3. Never associate with those who are unable to arrange their own affairs.

If your team employs a person who fails in all his endeavors, then you can predict that in a few years you will also face a collapse or large losses. For pathological losers, even if they are honest and intelligent, there is a characteristic unconscious programming, immaturity and unwillingness to take responsibility for their lives. This is already social psychosomatics.

4. Never put a fool on your team. You need to stay away from him in work and in your personal life. Otherwise, unpredictable consequences for the manager may occur.

5. Never hire someone who is frustrated about you on your team.

Do not be guided in the selection of personnel by dedication, flattery or sincere love. These people can turn out to be untenable in difficult work situations. It is necessary to choose those who believe in their work, who use work to achieve their own interests, who want to make a career, improve their financial situation. Perfectly serving the leader (owner), he can achieve all these goals, satisfy personal egoism.

6. In order to earn money, prosper, you must be able to serve partners, cultivate your own demeanor.

The main tactic is not to please your partner, but to study his needs and interests and take them into account in business communication. It is necessary to build value relationships with the bearers of wealth and success.

7. You should never mix personal and business relationships, personal life and work.

An excellent leader must be distinguished by a refined taste in personal life and the highest rationality, an extraordinary style in the business sphere.

8. A true leader needs the mentality of the only person who has the absolute right to the final idea.

It is known that the largest projects of real leaders owe their success to his silence.

9. When making a decision, one must focus on global success for the company, ie. when the result will benefit everyone who works for the leader and whom he leads.

In addition, in order for the solution to be optimal, you need:

preservation of everything positive that has been created up to the present moment;

prudent rationality based on available funds;

rational intuition (if, of course, it is inherent in the leader, since this is already the quality of a leader - a leader)

10. The law must be observed, circumvented, adapted to it and used.

This formulation, despite its inconsistency, has a deep meaning and in any case means that the leader's activity should always be in the right field, but this can be done in different ways. The law is the power structure of society, the connective tissue between the leader and others, physically inclined "for" or "against" him.

11. You should always follow the plan to anticipate the situation, not pay too much attention to the wrong action.

In the absence of the strictest control on the part of the leader, the situation objectifies him and, ultimately, despite the fact that he could do everything, he does nothing and stress arises and develops rapidly.

12. It is always necessary to create everyday aesthetics because the achievement of excellence in small things leads to great goals.

The whole is achieved through the orderly coordination of the parts. Objects left in disarray are always protagonists. The leader, depriving himself of aesthetics, robs his aesthetic ability.

To lead effectively, you need to have proportionality in 4 areas: individual personal, family, professional and social.

13. In order to avoid the conflicts that lie in wait for us every day, we must not forget about 2 principles: avoid hatred and revenge; never take someone else's that does not belong to you in accordance with the intrinsic value of things.

In general, all leaders, merchants and businessmen, regional and party leaders can be divided into 2 classes:

The first class consists of persons who, at their core, in their activities pursue personal and (or) social humanistic, moral goals.

The second class pursues personal and (or) social egoistic, monopolistic goals (in the interests of a group of individuals).

The first class of persons is able to realize the need to use the rules and recommendations discussed above. A significant part of these people, due to their decency and rational intuition, already use them, even without being familiar with these recommendations.

The second group of persons, who can be conditionally called new Russians ("NR"), are incapable of realizing this problem due to their personal qualities and due to the absence, unfortunately, of a civilized socio-economic environment in the country:

Communication with this group has a number of negative aspects, because "NR" have a number of negative professionally important qualities (Table 23).

Table 23

Negative vocationally important qualities (PVK) "HP"

These negative aspects of communication cause a number of conflicts, which are not always personal in nature and, due to the mass and often specificity, give rise to a number of already social, departmental and state problems and, ultimately, affect the psychological safety of leaders as individuals and even national security of the country. This situation can be reversed only through the purposeful formation of a civilized socio-economic environment with an orientation towards humanistic, moral, national goals and widespread propaganda of the achievements of ontopsychology in the field of forming the personality of top-level leaders. The ultimate goal of this process is to change the value orientations of the widest circles of the population. National security is obviously affected by the ratio of the number of persons of the first and second class. It is quite possible that at present the number of persons in the second group is greater than in the first. At what excess of the number of persons in the first class over the second can national security be ensured is a difficult question. Perhaps, in this case, the standard condition for the reliability of static hypotheses should be fulfilled (95%). In any case, when the above activities are carried out, the number of persons in the first class will increase, and in the second, it will decrease, and this process itself will already have a beneficial effect.

Mironova E.E. Collection of psychological tests. Part 2.

Computer networks and telecommunications

A computer network is a combination of several computers for the joint solution of information, computing, educational and other tasks.

Computer networks gave rise to substantially new information processing technologies - network technologies. In the simplest case, networking technologies allow the sharing of resources - high-capacity storage devices, printing devices, Internet access, databases and data banks. The most modern and promising approaches to networks are associated with the use of the collective division of labor when working with information - the development of various documents and projects, management of an institution or enterprise, etc.

The simplest type of network is the so-called peer-to-peer network that provides communication between personal computers of end users and allows sharing drives, printers, files. More developed networks, in addition to computers of end users - workstations - include special dedicated computers - servers ... Server is a computer that performs special functions of servicing other computers in the network in the network - workersantion. There are different types of servers: file servers, telecommunication servers, servers for performing mathematical calculations, database servers.

A very popular and extremely promising technology for processing information in the network today is called "client-server". The client-server methodology assumes a deep separation of the functions of computers in the network. In this case, the function of the "client" (which is understood as a computer with the appropriate software) includes

Providing a user interface focused on specific job responsibilities and user powers;

Formation of requests to the server, and not necessarily informing the user about it; Ideally, the user does not at all delve into the technology of communication of the computer he is using with the server;

Analysis of server responses to requests and presentation to the user. The main function of the server is to perform specific actions on requests

client (for example, solving a complex mathematical problem, searching for data in a database, connecting a client with another client, etc.); however, the server itself does not initiate any interactions with the client. If the server to which the client has contacted is unable to solve the problem due to lack of resources, then ideally he himself finds another, more powerful server and transfers the task to him, becoming, in turn, a client, but not informing about it unnecessarily initial client. Note that the "client" is not at all a remote server terminal. The client can be a very powerful computer, which, due to its capabilities, solves problems on its own.

Computer networks and network information processing technologies have become the basis for the construction of modern information systems. A computer now should be considered not as a separate processing device, but as a "window" into computer networks, a means of communication with network resources and other network users.

Local area networks (LAN computers) unite a relatively small number of computers (usually from 10 to 100, although sometimes much larger ones are found) within the same premises (educational computer class), building or institution (for example, a university). The traditional name is local area network (LAN)

Distinguish:

Local area networks or LANs (LAN, Local Area Network) are geographically small networks (room, floor of a building, building or several buildings located nearby). As a rule, a cable is used as a data transmission medium. However, wireless networks have been gaining popularity lately. The proximity of computers is dictated by the physical laws of signal transmission over LAN cables or the power of the transmitter of wireless signals. LANs can combine from a few units to several hundred computers.

The simplest LAN, for example, might consist of two PCs connected by cables or wireless adapters.

Internets or network complexes are two or more LANs connected by special devices to support large LANs. They are, in fact, networks of networks.

Wide Area Networks - (WAN, Wide Area Network) LANs connected by means of remote data transmission.

Corporate networks are global networks run by one organization.

From the point of view of the logical organization of the network, there are peer-to-peer and hierarchical.

The creation of automated enterprise management systems (ACS) had a great influence on the development of drugs. ACS include several automated workstations (AWS), measuring complexes, control points. Another important field of activity in which drugs have proven their effectiveness is the creation of educational computer technology classes (CUVT).

Due to the relatively short lengths of communication lines (as a rule, no more than 300 meters), it is possible to transmit information over the LAN in digital form with a high transmission rate. At long distances, this method of transmission is unacceptable due to the inevitable attenuation of high-frequency signals; in these cases, you have to resort to additional technical (digital-to-analog conversions) and software (error correction protocols, etc.) solutions.

Characteristic feature LS - availability of a high-speed communication channel connecting all subscribers for transmitting information in digital form. Exists wired and wirelesschannels. Each of them is characterized by certain values \u200b\u200bof parameters essential from the point of view of drug organization:

Data transfer rates;

Maximum line length;

Interference immunity;

Mechanical strength;

Convenience and ease of installation;

Cost.

Currently commonly used four types of network cables:

Coaxial cable;

Unprotected twisted pair;

Protected twisted pair;

Fiber optic cable.

The first three types of cables carry an electrical signal over copper conductors. Fiber optic cables carry light through glass fibers.

Wireless communication on microwave radio waves can be used to organize networks within large rooms such as hangars or pavilions, where the use of conventional communication lines is difficult or impractical. In addition, wireless links can connect remote LAN segments at distances of 3-5 km (with a wave-channel antenna) and 25 km (with a directional parabolic antenna), subject to line of sight. Wireless networking is significantly more expensive than conventional networking.

For organizing training LANs, twisted pair is most often used, like itself! cheap because the requirements for data transfer rate and line length are not critical.

To communicate with computers using LAN communication lines, you need network adapters (or, as they are sometimes called, network playou). The most famous are: adapters of the following three types:

ArcNet;

Topic 9. Telecommunications

Lecture plan

1. Telecommunications and computer networks

2. Characteristics of local and global networks

3. System software

4. OSI model and communication protocols

5. Data transmission media, modems

6. Possibilities of teleinformation systems

7. Possibilities of the World Wide Web

8. Prospects for creating an information highway

Telecommunications and computer networks

Communication is the transfer of information between people, carried out using various means (speech, symbolic systems, communication systems). As the development of communication, telecommunications appeared.

Telecommunication is the transmission of information over a distance using technical means (telephone, telegraph, radio, television, etc.).

Telecommunications are an integral part of the industrial and social infrastructure of the country and are designed to meet the needs of individuals and legal entities, government bodies in telecommunications services. Thanks to the emergence and development of data transmission networks, a new highly efficient way of interaction between people has appeared - computer networks. The main purpose of computer networks is to provide distributed data processing, to increase the reliability of information and management solutions.

A computer network is a collection of computers and various devices that provide information exchange between computers in a network without using any intermediate storage media.

Moreover, there is a term - a network node. A network node refers to a device that is connected to other devices as part of a computer network. Nodes can be computers, special network devices such as a router, switch or hub. A network segment is a part of the network bounded by its nodes.

A computer in a computer network is also called a "workstation." Computers in a network are subdivided into workstations and servers. At workstations, users solve application problems (work in databases, create documents, do calculations). The server serves the network and provides its own resources to everyone network nodes including workstations.

Computer networks are used in various fields, affect almost all spheres of human activity and are an effective tool for communication between enterprises, organizations and consumers.

The network provides faster access to various sources of information. Network usage reduces resource redundancy. By linking several computers together, you can get a number of advantages:

· Expand the total amount of available information;

· To share one resource by all computers (common database, network printer, etc.);

· Simplifies the procedure for transferring data from computer to computer.

Naturally, the total amount of information accumulated on computers connected to a network is incomparably larger than one computer. As a result, the network provides a new level of employee productivity and effective communication between the company and manufacturers and customers.

Other purposes of a computer network is to provide efficient presentation of various computer services to network users by organizing their access to resources distributed in this network.

In addition, the attractiveness of networks is the availability of e-mail and work scheduling programs. They enable managers of large enterprises to interact quickly and efficiently with a large staff of their employees or business partners, and planning and adjusting the activities of the entire company is carried out with much less effort than without networks.

Computer networks as a means of realizing practical needs find the most unexpected applications, for example: sale of air and railway tickets; access to information from reference systems, computer databases and data banks; ordering and buying consumer goods; payment of utility bills; exchange of information between the teacher's workplace and students' workplaces (distance learning) and much more.

Thanks to the combination of database technologies and computer telecommunications, it became possible to use the so-called distributed databases. Huge amounts of information accumulated by mankind are distributed in various regions, countries, cities, where they are stored in libraries, archives, information centers. Usually, all large libraries, museums, archives and other similar organizations have their own computer databases, in which the information stored in these institutions is concentrated.

Computer networks allow access to any database that is connected to the network. This saves netizens from having to keep a gigantic library and makes it possible to significantly increase the efficiency of work in finding the necessary information. If a person is a user of a computer network, then he can make a request to the relevant databases, receive an electronic copy of the necessary book, article, archival material over the network, see what paintings and other exhibits are in this museum, etc.

Thus, the creation of a single telecommunications network should become the main direction of our state and be guided by the following principles (the principles are taken from the Law of Ukraine "On Communications" dated 20.02.2009):

1. consumer access to public telecommunications services that
   they need to meet their own needs, participate in political,
   economic and social life;
2. interaction and interconnection of telecommunication networks to provide
   communication capabilities between consumers of all networks;
3. ensuring the stability of telecommunication networks and the management of these networks with
   taking into account their technological features on the basis of uniform standards, norms and rules;
4. state support for the development of domestic production of technical
   telecommunication facilities;

5. promotion of competition in the interests of consumers of telecommunications services;

6. increase in the volume of telecommunication services, their list and the creation of new jobs;

7. implementation of world achievements in the field of telecommunications, attraction, use of domestic and foreign material and financial resources, the latest technologies, management experience;

8. assistance in expanding international cooperation in the field of telecommunications and the development of a global telecommunications network;

9. ensuring consumers' access to information on the procedure for obtaining and the quality of telecommunication services;

10. efficiency, transparency of regulation in the field of telecommunications;

11. creation of favorable conditions for activities in the field of telecommunications, taking into account the characteristics of technologies and the telecommunications market.

Computer network (CS) - a set of computers and terminals connected using communication channels into a single system that meets the requirements of distributed data processing.

In general, under telecommunication network (TS) understand a system consisting of objects that perform the functions of generating, transforming, storing and consuming a product, called points (nodes) of the network, and transmission lines (communications, communications, connections) that transfer the product between points.

Depending on the type of product - information, energy, mass - there are respectively information, energy and material networks.

Information network (IS) - a communication network in which information is the product of the generation, processing, storage and use of information. Traditionally, telephone networks are used to transfer sound information, images - television, text - telegraph (teletype). Currently, information integrated service networks, allowing the transmission of sound, image and data in a single communication channel.

Computing network (BC) - information network, which includes computing equipment. Computing network components can be computers and peripheral devices that are sources and receivers of data transmitted over the network.

The sun is classified according to a number of characteristics.

• 1. Depending on the distance between the nodes of the network, the aircraft can be divided into three classes:
  • · local (LAN, Local Area Network) - covering a limited area (usually within the distance of stations no more than a few tens or hundreds of meters from each other, less often by 1 ... 2 km);
  • · corporate (enterprise scale) - a set of interconnected LANs covering the territory on which one enterprise or institution is located in one or more closely located buildings;
  • · territorial - covering a significant geographic area; among the territorial networks, regional (MAN - Metropolitan Area Network) and global (WAN - Wide Area Network) networks can be distinguished, having regional or global scales, respectively.

The global Internet is especially distinguished.

2. An important feature of the classification of computer networks is their topology, which determines the geometric location of the main resources of a computer network and the connections between them.

Depending on the topology of the nodes' connections, there are bus (backbone), ring, star, hierarchical, arbitrary structures.

Among LANs, the most common:

• · bus (bus) - a local network in which communication between any two stations is established through one common path and the data transmitted by any station simultaneously becomes available to all other stations connected to the same data transmission medium;
• · ring - the nodes are connected by a circular data line (only two lines are suitable for each node). The data passing through the ring becomes available to all network nodes in turn;
• · star - there is a central node, from which data transmission lines diverge to each of the other nodes.

The topological structure of a network has a significant impact on its throughput, network resilience to equipment failures, logical capabilities and network cost.