Local network - what functions does it perform? What functions does a local network server perform: main points

>>Informatics: How it works computer network

How does a computer network work?

Introduction

Having studied the first part of the “Informatics and ICT” course, you have mastered only some sections of this large scientific and applied field. This textbook will introduce you to new sections of the subject and help you acquire new skills in using information and communication technologies.

This school year you will get to know computer networks, which are used to transmit information. Technologies for working with information in computer networks are called communication technologies. As a result, you will fully understand the meaning of the term “information and communication technologies” - ICT.

A very important application of computer technology is information modeling. You will soon learn what a model is, how it is created on a computer and what it is used for. information models, what ICT tools are used for information modeling. These tools include database management systems (DBMS) and spreadsheet processors. Using a DBMS, information repositories are created on a computer, which are called databases. Table processors are used to organize calculations in spreadsheets. If such calculations relate to some real process, then in this case we can say that a mathematical model of this process is implemented in the spreadsheets.

Management is another broad area of use computers. With the help of computers, airplanes, rockets, industrial installations, production teams, economic sectors, etc. are controlled. It turns out that such diverse control options have general laws. They were discovered in the science of cybernetics. You will become familiar with the basic concepts of this science.

Any control occurs according to certain rules, which are called a control algorithm. An algorithm written in a programming language that a computer can “understand” is called computer program. In this part of the course you will learn how to build algorithms and write simple programs in the Pascal programming language.

Inventions various means and tools for storing, transmitting and processing information have been carried out from ancient times to the present day. You will learn about the history of such inventions in the last chapter of the textbook. The history of computers and ICT dates back to the mid-20th century. From this time on, the process of informatization of various areas of human activity begins, and the formation of an information-oriented society takes place. Problems information society studies a branch of computer science called social informatics. You will learn about some issues in social informatics at the end of our course.

So, let's continue our journey across the ocean Computer Science. You visited and explored some of the continents and islands in this ocean in the first part of the journey. But there are still uncharted lands, white spots on the map of the ocean of knowledge. Together with our brave captain - Tochka-RU, you will have to visit these lands and put their detailed description on the knowledge map. Good luck to you on this difficult but very interesting journey!

Chapter 1

Transfer of information in computer networks

Here you will learn:

♦ how computer networks are structured;
♦ what are networks used for?
♦ what is the Internet;
♦ how not to get lost on the Internet.

§ 1. How a computer network works

Main topics of the paragraph:

♦ what is a computer network;
♦ local networks;
♦ global networks.

What is a computer network

You already know that when a computer is running, information is constantly exchanged between its component devices. The transfer of information between the user and the computer is carried out through keyboard, display, printer and other input/output devices. Now you will learn how computers exchange information with each other.

A system of computers connected by information transmission channels is called a computer network.

Local networks

Small computer networks operating within one room, one enterprise, are called local networks (LAN). Usually computers one local network separated from each other by a distance of no more than one kilometer.

A local network allows users not only to quickly exchange data with each other, but also to more efficiently use the resources of networked computers. Such resources could be disk memory, printing device, scanner and other technical means, as well as software and any information in files.

From the point of view of organizing the interaction of individual drug elements, two types of such systems are distinguished:

Peer-to-peer network; in it all connected computers have equal rights;
network with a dedicated server.

A user of a peer-to-peer network can have access to the resources of all computers connected to it (if these resources are not protected from unauthorized access).

In school computer classes, a LAN with a dedicated server is most often used, organized according to the following principle: there is one central machine, which is called a server, and many computers connected to it - workstations. The central machine usually has a large disk memory; devices that are not on workstations are connected to it: a printer, a scanner, a modem for accessing the global network, etc. The server stores software and other information that can be accessed by network users. The name “server” comes from the English “server” and is translated as “serving device”.

Many enterprises operate information systems based on local networks. For example, in a large shopping center, a database containing information about the goods in stock is stored on the server. Workstations are installed in sales departments. At the request of sellers, they receive information from the server about the availability of the desired type of product. WITH workstation Information about the sold product is transmitted to the server. After this, the server makes the appropriate changes to the database.

The basis of the LAN software is the network operating system. The most important task of a network OS is to support such a mode of operation of the LAN so that users working in it can use shared network resources without interfering with each other.

Global networks

Another type of computer networks are global networks. Further we will talk about them.

The global network connects many local networks, as well as individual computers, not included in local networks. The size of global networks is not limited: there can be networks from regional to worldwide.

A global computer network is called a telecommunications network, and the process of exchanging information over such a network is called telecommunications (from the Greek “tele” - “far”, “far” and the Latin “comunicato” - “communication”).

The organization of communications in global networks is similar to the organization telephone communication. Each subscriber's phone is connected to a specific switch node. Communication between switches is organized in such a way that any two subscribers, no matter where they are, can talk to each other. And so telephone network"covers" the whole world. Computer networks work similarly. The personal computer of a network user (it can also be called a subscriber) is connected to a specific network node. The nodes are connected to each other, and this connection operates constantly. In Fig. 1.1 network nodes are designated U1, U2, etc., and subscriber computers are designated A11, A12, etc.

Networks serving some industry of the state (education, science, defense, etc.) are called industry (corporate) networks. If a network exists within a certain region, then it is called regional.

Each regional or industry computer network usually has connections with other networks. For this purpose, one of the network nodes acts as a gateway. It is connected by a communication line with similar nodes of other networks*.

*The need for a gateway only exists if the connected networks use different protocols (agreements). The need for a gateway only exists if the connected networks use different protocols (agreements).

There is a global system of computer networks through which you can establish communications with the most distant corners of the planet. This system is called “Internet” (English: “net” - network; “Internet” - association of networks). We'll talk about the Internet a little later.

Briefly about the main thing

A computer network is a set of computers connected by information transmission lines.

Computer networks are local and global.

In peer-to-peer local networks, all computers have equal rights.

A local network with a dedicated computer includes a server and many workstations. The server is used as a repository for shared information resources, and also contains some technical devices general access.

A global (telecommunications) network is a system of interconnected local networks and computers of individual users. Personal computers users (subscribers) are connected to global network nodes.

There are regional and industry networks. Currently, most of them are united in a global system called the Internet.

Questions and tasks

1. What is a computer network?
2. How does a local network work? What functions does it perform?
3. What is a global network?
4. What is an industry network; regional network?
5. What is the name of the worldwide network, which unites most of the networks existing in the world?
6. Invent various ways connecting four computer servers to a network. Find a method that provides the shortest route for transmitting information between any two subscribers.

I. Semakin, L. Zalogova, S. Rusakov, L. Shestakova, Computer Science, 9th grade
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The term “local network” means a communication system that connects several computers within one room, building or several nearby buildings of one enterprise. Cables, telephone lines, or radio channels can be used to connect computers. Thanks to this association, users: get access to information on all computers connected to the LAN (programs, folders, files); can share modems, printers, scanners […]

gain access to information on all computers connected to the LAN (programs, folders, files);
can share modems, printers, scanners and other peripheral devices.

Main types of local networks

LANs are classified according to various criteria. Let's look at what types of local networks there are, depending on the presence of a control computer:

Peer-to-peer – they are relevant for combining a small number of computers (up to 10) and in cases where increased information security is not required. At the same time, users have equal rights of access to information and independently decide which resources of their computer to open. general access. Such networks are extremely simple to install and operate, but ensure reliable protection the data in them is problematic.
Hierarchical, server-based - such LANs provide high performance and reliability of information storage with a large number of users. They have a central computer - a server (one or more) designed for:

centralized management of LAN, information exchange and resource distribution;
connecting all peripheral devices;
storage special programs, applications and the main part of the LAN information;
developing message transmission routes within the network.

Let's look at what types of local networks there are by type of communication:

Wired - such LANs use twisted pair, fiber optic or coaxial cable as communication channels. Twisted pair consists of 2 twisted conductors. She has a short throughput(up to 1 Mbit/s), but resistant to interference. Twisted pair cables of classes 5, 5e, 6, 6e, 7 have higher throughput (from 100 Mbit/s). Coaxial cable contains a central conductor and an insulating coating, on which another conductor (screen) is applied on top. This can be foil or braided copper wire. Fiber optic cable provides speeds above 10 Gbps. It contains a thin cylinder of glass, on which a shell with a different refractive index is applied.
Wireless - they work with data transmission in the infrared range or via radio channels. Such networks quickly transmit information, but are vulnerable to interference from other sources of the same frequency and unauthorized external access.

What types of local network topology are there?

Classification of local networks by topology (structure) is carried out according to the type of computer connection.

The network configuration can be:

In the form of a bus - when a cable sequentially connects computers to each other. Connection and exchange of information is carried out through single channel connection - bus. This topology is simple and economical and ensures fast information transfer. But when a cable is damaged, problems arise throughout the network, and identifying the location of the fault is not easy.
Star-shaped - when each machine is connected by a separate cable to a server located in the center of the network, which centrally manages the entire network. This structure is more resistant to faults and unauthorized access, does not cause difficulties in determining the location of problems and ensures fast data transfer from workstations to the server. It is widely used when creating a local network. The disadvantages of this structure are low speed data transfer between individual workstations and the dependence of the operation of the entire network on the characteristics of the server.
In the form of a ring - when network machines are sequentially connected to each other and to the server or jointly perform the functions of the server. Such schemes are characterized by ease of management and quick access to data, but if an individual machine fails or a channel failure between 2 nodes occurs, problems arise in the operation of the entire network. To ensure that the communication channel between other computers is not interrupted, special transition connections must be used in such networks.
Mesh – a structure in which communication lines are established with all nearby machines. In such systems, only workstations that intensively exchange information are directly connected. Machines not connected by direct connections exchange data using transit transfers using intermediate computers. This structure is suitable for connecting a large number of machines and is often used when organizing global or large local networks. It is maximally resistant to overloads and failures.
Tree-shaped – is a combination of several topologies (bus-star, star-ring). The base of the LAN tree is at the point where the data communication lines are assembled. Such networks are in demand when it is impossible to organize basic topologies.
Mixed (hybrid) - when creating large LANs, arbitrary connections between workstations are often used, but subnets with a standard structure can be distinguished.

Now you know what types of local networks exist, how they differ from each other, what are the advantages and disadvantages of each individual type. To decide on the choice of LAN that suits you, consult with our specialists. You can also instruct us

Do you want to optimize your company's work as much as possible? You just need to install local computer network. This will allow employees to use the computer equipment, databases and programs needed in their work. Regardless of the location of the workplace, team members will be able to transmit information, forward email etc.

Main functions and advantages of LAN

The main functions of a LAN are identified. This:

prompt delivery of documentation (in electronic form) to all branches of the organization;
constant communication between the team. The LAN will ensure communication between employees located in
head office and branches;
the ability to access office equipment (printers, faxes, modems) from different points office;
automation of the use of all databases (archives, storage);
providing public access to the Internet;
remote communication (teleconferences). This is important for meetings and conferences;
possibility of remote network administration.

Current LAN installation price available on the website of the company providing such a service. Please read the price list carefully before submitting your application.

After installing the LAN, you get the opportunity to quickly receive and send any information. Plus, by connecting all computers to a single communication network, the overall speed of work significantly increases.

What does LAN installation involve? The work consists of several stages:

visit of a specialist to the site;
system design;
selection of necessary equipment;
direct installation work;
adjustment and configuration of equipment;
testing and delivery.

LAN installation should only be carried out by professionals. This process requires strict adherence to technology. The slightest mistake will lead to the fact that the office equipment simply will not function. This is unacceptable downtime in the company's work and losses.

Firms offering LAN installation must have a license to engage in such activities. An important factor is the minimum time frame within which the work will be completed. After the installation is completed, it is wiser to conclude a contract for system maintenance.

After connecting the computers to unified network, you will immediately feel the difference. The work will be done much faster. LAN capabilities allow you to connect devices to it in different offices, cities and even countries.

About the fact that all modern world is a giant virtual web known to, perhaps, every schoolchild. The times when the exchange of information was carried out on the “hand to hand” principle, and the main data carrier was a stamped paper folder, are in the distant past, but now countless virtual highways connect all points of the planet into a single information system– computer data transmission network.

What is a computer network?

In a general sense, a computer data network is a communication system of various computer technology(including PC and user office equipment) necessary for automatic exchange data between end users, as well as remote control functional units and software this network.

There are a great many ways to classify computer networks (by architecture, type of transmission medium, network operating systems etc.), however, delve into the jungle of theory network technologies we won’t: particularly inquisitive users will always be able to find this information in educational literature. Here we will limit ourselves to the simplest classification of networks depending on their length.

So, computer networks are divided on a territorial basis into local and global:

A global computer network is a data transmission network that covers the entire world (or individual large regions) and unites an unlimited number of unconnected subscribers.

A local computer network is a collection of PCs and network equipment, designed to transmit data to a finite number of users. By the way, the term “local network” was assigned to the system in those days when the capabilities of the equipment did not allow organizing such communications for subscribers remote over long distances, but now local computer networks are used both for organizing local communications (within one building or organization), This covers entire cities, regions and even countries.

Types of computer networks

According to the method of organizing communication between subscribers, the topology of computer networks distinguishes the following local network schemes:

Where the network nodes are computers, office equipment and various network equipment.

More complex topologies (such as tree network, mesh network, etc.) are built by various connections of the three elementary types of local network.

Local network functions

We will not talk about the purpose of global networks and how the Internet benefits the world: the main functions of the World Wide Web are already well known to every user, and detailed description More than one book could be devoted to all the possibilities of the network.

At the same time, home networks are unfairly deprived informational attention, and many users do not understand why they need a local network at all.

So, the main functions of a local network:

- Optimization of the workflow. Thus, a home local network, organized, for example, in an office, provides all its employees with the opportunity to remotely exchange data, as well as sharing all types of office equipment;
- Communication. Of course, local networks will not be able to completely replace “Internet connection”, but in cases where you need to organize your own, closed from external users, communication channel (for example, a forum for corporate employees), local networks are simply irreplaceable;

- Possibility of remote administration. Thus, a corporate local network allows one specialist to provide technical support several dozen different devices;
- Saving. Agree, it is more logical to pay for an Internet connection once and provide all employees of the organization (user devices) with the opportunity to free access, than to pay for access to world wide web each employee (gadget) individually;
- Games, security of data exchange, user comfort and much more.

Thus, the local network is very, very useful tool in any field of activity. In fact, it was local networks that replaced the well-known “pigeon mail” both at any enterprise and between friends (after all, this is a much more functional alternative to tapping on the battery and “cactus” signals on the windowsill). And our lessons will help you not only create a local network from scratch with your own hands, but also solve much more complex administration issues corporate networks and settings different types network equipment.