How to create a local area network between two computers. Do-it-yourself local network: General rules for building a home network and its main components Connecting a PC to a network
1. Types of computer networksOne of the most significant achievements of the last century is the development of information technologies - computer technologies for storing, converting and transmitting information. The most important role in the informational leap of mankind was played by the creation of communication computer networks.
A set of computers interconnected by information transmission channels and distributed over a certain territory is called a computer network. Numerous computer networks that currently exist are usually divided according to the so-called territorial basis. According to this gradation, networks are:
GAN(Global Area Network - global network), a common planetary connection of computer networks - the Internet;
WAN(Wide Area Network - a large-scale network), a continental association of computer networks at the state level;
MAN(Metropolitan Area Network - long-distance network), long-distance and regional association of computer networks;
LAN(Local Area Network - local area network) a network connection that usually operates within the walls of one organization.
WAN and MAN– regional networks. The division into WAN and MAN computer networks is currently very arbitrary, since now each regional network is, as a rule, part of a global network.
Many organizations interested in protecting information from unauthorized access (for example, military, banking, etc.) create their own, so-called corporate networks. A corporate network can unite thousands and tens of thousands of computers located in different countries and cities (an example is the network of Microsoft Corporation, MSN).
2. Local computer network
An important distinguishing feature of any local area network is that it is not necessary to use the telephone network to connect computers in such a network - the computers are located close enough to each other and are connected by a cable. Local networks in production practice play a very important role. Through the LAN, the system combines personal computers located at many remote workstations that share equipment, software and information. Workplaces of employees are no longer isolated and are combined into single system. Consider the advantages obtained by networking personal computers in the form of an intra-industrial computer network.
Resource Sharing: Resource Sharing allows you to use resources sparingly, such as controlling peripherals such as a laser printer, from all connected workstations.
Data separation: data sharing provides the ability to access and manage databases from peripheral workstations that need information.
Separation of software: separation of software, provides the ability to simultaneously use centralized, previously installed software.
Processor Sharing: Processor sharing allows processing power to be used by other systems on the network. The opportunity provided lies in the fact that the available resources are not "attacked" instantly, but only through a special processor available to each workstation.
Multi-User Mode: The multi-user features of the system facilitate the simultaneous use of centralized applications previously installed and managed, for example, if a user of the system is working on other jobs, then the current work in progress is relegated to the background.
Email: via Email there is an interactive exchange of information between the workstation and other stations installed in the computer network.
3. Local network components
A local network usually consists of the following components:
1. File Server- a central machine with a large disk memory.
2. Workstations- many computers connected to the central machine (file server).
3. Network boards. In each computer that we are going to connect to the local network, an additional network controller card should be installed. Its purpose, like any other controller, is to convert the signals coming from the network into signals coming to the computer blocks, as well as to perform the reverse operation. The network card is inserted into a free slot on the motherboard, and a coaxial cable is connected to its socket, located on the back of the system unit. The server needs a high performance network card, i.e. its performance should be greater than the performance of network cards for local workstations.
4. Connection cable. The cable connects the network boards of workstations (computers) to each other. Cable systems are the basis of communications. When choosing the type of cable, the following indicators are taken into account:
o installation and maintenance cost,
o information transfer rate,
o restrictions on the value of the distance of information transmission,
o security of information transfer.
The main indicators of three typical media for information transfer are shown in the table.
5. Periphery equipment. Peripheral equipment (for example, a laser printer, plotter, and others) is connected to the file server.
6. Computer network operating system. Just like any computer system needs an operating system, a LAN needs its own operating system. On the file server, you need to install a special driver program to manage the network. When the network boots up, the network driver must be enabled first. The network driver should be installed on all other computers on the network, but on the server it is installed in its full form, and all network parameters are set there. Of the most popular network programs, it should be noted programs (and their corresponding networks) from Novell, Microsoft - Windows / NT, as well as a domestic invention - the Iola network.
7. Application software must be designed specifically for computer networks. It is necessary to provide the ability to control access to the available system resources from all connected workstations.
4. Topology of local networks
The most important characteristic of a local area network is its topology, in other words, the way computers are connected to each other. The type of topology determines the performance and reliability of the network of workstations, for which the access time to the file server is also important.
There are networks with the topology " Star when all other machines on the same network connect to the central machine. A clear disadvantage of such a network organization is the limited number of machines connected to the server and the inoperability of the entire network when the server fails.
There are networks with topology " Ring”, when all computers are connected in series in a ring and any of them can become a server. The disadvantage of this configuration is that it is difficult to include new users in the network.
Currently, networks with a topology called common bus and with the so-called tree topology. Any of the machines included in such networks can become a server; in addition, almost unlimited network expansion is possible - the connection of new users does not entail configuration changes.
Along with the well-known topologies of computer networks in practice, it is also used combined.
5. Means of interaction in local networks
In each local network, there is always the possibility of exchanging text messages and files between users, which is an important advantage for any organization.
Physically, data exchange in the network is carried out as follows: each of the machines included in the network has its own number - an identifier; information from a particular computer enters the network in the form of separate portions, they are called packets. Packets are supplied with information about which machine on the network they are intended for. Then the packet moves freely through the network, comparing its number with the identifier of each specific machine. If they match, the message is transmitted to the given machine. It should be noted that the distribution of data and messages over the network is possible simultaneously for all users of this network: you can, for example, send a message not to one specific user, but to a group of users or to all network users at the same time, including yourself.
With the advent of a new class of personal computers - portable computers "Notebook" the question arose of how these computers can be connected to each other in a local network. The problem was solved in 1992 with the advent of wireless LANs. Some of these networks operate on the basis of information transfer between computers in the microwave range (SHF). Some disadvantage of this method of communication is the interference created by other devices operating on the same frequency. Another way to organize wireless local area networks is to transmit information using infrared rays. It is clear that an important limitation when working in such a network is the presence of a constant line of sight between the computer - the transmitter and the computer - the receiver of information.
Currently, there are local networks operating on the same principle and with the same software on which the global Internet operates. These local networks are collectively known as the Internet.
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_1.jpg" alt=">Connecting computers to a local network. Organization of user work in local computer networks . Performed:"> Объединение компьютеров в локальную сеть. Организация работы пользователей в локальных компьютерных сетях. Выполнила: Преподаватель ГБОУ СПО «Самарский техникум кулинарного искусства» Иванова Н.Б.!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_2.jpg" alt=">A computer network is a connection between computers to exchange information and share resources ( printer, modem,"> Компьютерная сеть – соединение компьютеров для обмена информацией и совместного использования ресурсов (принтер, модем, дисковая память и т.д.).!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_3.jpg" alt=">Local Area Network"> Локальная сеть Локальная сеть объединяет компьютеры установленные в одном помещении (учебный класс, офис и т.п.), в одном здании или в нескольких близко расположенных зданиях. Обычно компьютеры локальной сети расположены на расстоянии не более одного километра. При увеличении расстояния используется специальное оборудование.!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_4.jpg" alt=">Local networks are divided into: peer-to-peer; networks"> Локальные сети по способу взаимодействия компьютеров подразделяются на: одноранговые; сети с выделенным сервером.!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_5.jpg" alt=">Client is a task, workstation or computer network user. In progress customer data processing"> Клиент - задача, рабочая станция или пользователь компьютерной сети. В процессе обработки данных клиент может сформировать запрос на сервер для выполнения сложных процедур, чтения файлов, поиск информации в базе данных и т.д. Сервер, определенный ранее, выполняет запрос, поступивший от клиента. Результаты выполнения запроса передаются клиенту. Сервер обеспечивает хранение данных общего пользования, организует доступ к этим данным и передает данные клиенту.!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_6.jpg" alt=">Peer-to-Peer LAN In a peer-to-peer LAN, all computers are peers. Shared devices may"> Одноранговая локальная сеть В одноранговой локальной сети все компьютеры равноправны. Общие устройства могут быть подключены к любому компьютеру в сети.!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_7.jpg" alt=">Advantages of peer-to-peer networks: low cost; high reliability. Disadvantages peer-to-peer networks:"> Достоинства одноранговых сетей: · низкая стоимость; · высокая надежность. Недостатки одноранговых сетей: · зависимость эффективности работы сети от количества станций; · сложность управления сетью; · сложность обеспечения защиты информации; · трудности обновления и изменения программного обеспечения станций!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_8.jpg" alt=">Dedicated server network Dedicated server network structure">!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_9.jpg" alt=">Network with dedicated server Server ) is a computer distributing"> Сеть с выделенным сервером Сервер (от англ. server - обслуживающее устройство) - компьютер, распределяющий ресурсы между пользователями сети. В сервере установлен мощный процессор, большая оперативная и дисковая память, хранится основная часть программного обеспечения и данных сети, которыми могут воспользоваться все пользователи сети.!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_10.jpg" alt=">Network with a dedicated server"> Сеть с выделенным сервером В качестве рабочих станций обычно используются менее производительные компьютеры с меньшей дисковой и оперативной памятью.!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_11.jpg" alt=">In networks with a dedicated server, client-server technology is implemented. On the server server software is installed:"> В сетях с выделенным сервером реализуется клиент-серверная технология. На сервере устанавливается серверное ПО: серверная операционная система; WEB-сервер (организация Интранет); прокси-сервер (обеспечение работы с Интернет рабочих станций); файл-сервер (обеспечение совместного доступа к файлам) и т.п. ПО сетей с выделенным сервером!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_12.jpg" alt=">Client software is installed on the workstation: operating system for workstations;"> На рабочей станции устанавливается клиентское ПО: операционная система для рабочих станций; клиентская часть прикладного ПО и т.п. ПО сетей с выделенным сервером!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_13.jpg" alt="> peer-to-peer networks);"> Наиболее распространены следующие способы соединения компьютеров: шина (как правило используется для одноранговых сетей); звезда (используется для любых локальных сетей). Аппаратное обеспечение сети!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_14.jpg" alt=">Connection type - "bus" The cable runs from one computer to another connecting computers and"> Тип соединения - «шина» Кабель проходит от одного компьютера к другому, соединяя компьютеры и периферийные устройства!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_15.jpg" alt=">Star connection type one central node.">!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_16.jpg" alt=">LAN Components"> Компоненты локальной сети Для организации локальной сети необходимо установить в каждый ПК сетевую плату и соединить все компьютеры с помощью специального кабеля.!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_17.jpg" alt=">LAN Components Sometimes the components necessary for connecting computers are already installed"> Компоненты локальной сети Иногда необходимые для связи компьютеров компоненты уже установлены на системной плате и тогда отдельная сетевая плата не нужна. В этом случае гнездо для сетевого кабеля расположено на задней стенке системного блока.!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_18.jpg" alt=">LAN Components Cables Coaxial cable - transmission rate up to 10 Mbps/ C. Twisted pair"> Компоненты локальной сети Кабели Коаксиальный кабель – скорость передачи до 10 Мбит/с. Витая пара - скорость передачи до 100 Мбит/с.!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_19.jpg" alt=">LAN Components Cable Connectors for Twisted Pair Coaxial Cable">!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_20.jpg" alt=">LAN Components Hubs (HUB or Switch) - serve"> Компоненты локальной сети Концентраторы (HUB или Switch) - служат для соединения компьютеров в сети. Концентратор может иметь !} different quantity connection ports (usually from 8 to 32).
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_21.jpg" alt=">LAN Components The overall network connection speed when using the HUB is determined by the speed"> Компоненты локальной сети Общая скорость соединения в сети при использовании HUB определяется скоростью самой медленной сетевой платы. Для Switch скорость соединения любой пары компьютеров определяется скоростью самой медленной сетевой платы в паре (группе).!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_22.jpg" alt=">Network software For LAN operation"> Программное обеспечение сети Для работы в локальной сети необходимо специальное сетевое программное обеспечение. В операционной !} Windows system already has everything you need to set up the network.
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_23.jpg" alt=">Network software ;"> Программное обеспечение сети Для организации локальной сети необходимо: определить имя Рабочей группы; присвоить каждому компьютеру уникальное в данной Рабочей группе имя и IP-адрес, а также установить адрес маски подсети (в некоторых случаях явный IP-адрес и адрес маски подсети можно не устанавливать).!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_24.jpg" alt=">Network Software This window is used to set the computer name and"> Программное обеспечение сети Данное окно используется для установки имени компьютера и Рабочей группы!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_25.jpg" alt=">Network Software These windows are used to set the explicit IP address and subnet mask settings">!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_26.jpg" alt=">This window is used to set the level of access to local computer resources"> Данное окно используется для установки уровня доступа к локальным ресурсам компьютера Режимы доступа к ресурсам сети!}
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_27.jpg" alt=">Local resource. Network users are denied access to computer resources. To ensure availability of local resources"> Локальный ресурс. Запрещается доступ к ресурсам компьютера пользователям сети. Для обеспечения доступности локальных ресурсов нужно установить переключатель в положение !} Shared resource. Shared resource. Allows the use of computer resources (disk memory and peripheral devices - printer, modem) to network users. To do this, you need to allow Share the folder. In this case, it is required to determine the access level. Modes of access to network resources
Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_28.jpg" alt=">Network Access Modes Read only Allows network users to open or copy files"> Режимы доступа к ресурсам сети Только чтение Позволяет пользователям сети открывать или копировать файлы и папки. Полный доступ Позволяет пользователям сети выполнять все операции над файлами, папками (переносить, удалять, редактировать, переименовать и т.п.). Доступ, определяемый паролем Данный режим предоставляет !} different categories users different access rights, such as read-only or full access.
Description of the presentation on individual slides:
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Topic: Combining computers into a local computer network. Organization of work of users in local computer networks. Compiled by: teacher of the SMT FSBEI HE "Kerch State Marine Technological University" Sharatova Natalya Vladimirovna
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A computer network is a collection of computers connected to each other using special equipment, which ensures the exchange of information between the computers of this group and is equipped with special communication software.
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Networks provide users with the opportunity not only to quickly exchange information, but also to collaborate on printers and other peripheral devices, and even to simultaneously process documents.
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The main characteristics of networks include: Bandwidth - the maximum amount of data transmitted by the network per unit of time. Throughput is measured in Mbps. Network response time - the time spent by the software and network devices to prepare for the transmission of information over a given channel. Network response time is measured in milliseconds.
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Computers can communicate with each other because there are sets of rules, or protocols, that help computers understand each other. Protocols are necessary for the communication process to proceed without errors. Protocols help define how information is sent and how it is received. A network protocol is a set of rules for organizing work on a computer network.
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Local area network (LAN - Local Area Network) - a network within an enterprise, institution, one organization. Regional network (MAN - Metropolitan Area Network) - a network within a city or region. Wide area network (WAN - Wide Area Network) - a network on the territory of a state or a group of states.
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workstation (client-machine, workplace, subscriber station, terminal) is a computer that a subscriber of a computer network directly works on. The network of workstations is represented by a set of workstations and means of communication that ensure the interaction of workstations with the server and with each other.
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A server is a computer that performs general computer network tasks and provides services to workstations. A server network is a collection of servers and communications that connect servers to the underlying data network.
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The underlying data communication network is a collection of means for transmitting data between servers. It consists of communication channels and communication nodes.
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A communication node is a set of means of switching and data transmission in one point. The communication node receives the data coming through the communication channels and transmits the data to the channels leading to the subscribers.
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A local area network is a system of interconnected computers operating within the same premises, building, or one organization. Local computer networks
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fast exchange information sharing of peripheral devices (printer, scanner, modem, etc.) simultaneous work with documents Based on the distribution of functions, local computer networks are divided into peer-to-peer and multi-rank
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In a peer-to-peer network, all computers are equal. Peer-to-peer networks are also called workgroups. A workgroup is a small team, so peer-to-peer networks often have no more than 10 computers. Types of LANs A dedicated server is a server that functions only as a server (excluding client or workstation functions). Peer-to-peer network Dedicated server network
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server-based peer-to-peer Computers are peers. Users independently decide which computer resources to make public. A computer used as a repository of shared information resources and allowing connection to shared technical devices. The local network
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Peer-to-peer network Computers in such a network are equal in relation to each other. Each user on the network decides for himself what resources of his computer he will provide for general use. The computer acts as both a client and a server.
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Server (from the English server - service device) - a computer that distributes resources between network users, used as a repository of common information resources and allowing you to connect to technical devices for general access.
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The server can provide various services, of which the following are the most well-known: storage and provision of files (file server); output to a printer (print server); receiving and forwarding fax messages (fax server); receipt, storage and transmission of e-mail messages (mail server); site hosting (web-server).
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Topology "Bus" A single cable is used along which all computers in the network are connected. The terminator is needed to absorb the transmitted signal at the ends. Simplicity If one computer fails, it will not affect the operation of the others Only one computer can transmit data at a time Breaking the cable causes the network to stop working When a large number of computers, the network is slow terminator terminator
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Tire. A communication channel that connects nodes into a network forms a broken line - a bus. Any node can receive information at any time, and transmit only when the bus is free. Data (signals) are transmitted by the computer to the bus. Each computer checks them, determining to whom the information is addressed, and accepts the data if they are sent to it, or ignores it. If the computers are located close to each other, then the organization of a CS with a bus topology is inexpensive and simple - you just need to lay a cable from one computer to another. Signal attenuation with increasing distance limits the length of the bus, and therefore the number of computers connected to it. Bus topology problems arise - when there is a break (disruption of contacts) at any point in the country; the network adapter of one of the computers fails and starts transmitting interference signals to the bus; you need to connect a new computer.
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Topology "Ring" Signals travel around the ring in one direction and pass through each computer (closed network). The cable has no free end and therefore no terminator is needed Each computer amplifies the signals by passing them on to the next computer If one computer fails, the entire network stops functioning
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Ring. The nodes are connected in a network of a closed curve. Data is transmitted in only one direction. Each node, among other things, implements the functions of a relay. He receives and transmits messages, and perceives only addressed to him. Using a ring topology, you can join a network a large number of nodes, solving the problems of interference and signal attenuation by means of the network card of each node. Disadvantages of the ring organization: a break anywhere in the ring stops the entire network; the transmission time of the message is determined by the successive operation time of each node located between the sender and the recipient of the message; due to the passage of data through each node, there is the possibility of inadvertent distortion of information.
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Topology "Star" Server Network management is centralized (there is a special central device (hub), from which "beams" go to each computer, i.e. each computer is connected to its own cable). If one computer fails, the network remains operational For large networks, cable consumption increases significantly If the server fails, the network stops functioning
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Star. Network nodes are connected to the center by beams. All information is transmitted through the center, which makes it relatively easy to troubleshoot and add new nodes without interrupting the network. However, the cost of organizing communication channels is usually higher here than for a bus and a ring.
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Topology "Tree" A hierarchical connection of nodes emanating from a common root node. There is only one route between any two nodes. high efficiency of use; the failure of one station or cable will not affect the operation of others; saving working time. a large amount of cable is required; reliability and performance is determined by the central node.
28 slide
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The combination of basic topologies - hybrid topology - provides a wide range of solutions that accumulate the advantages and disadvantages of the basic ones. In addition to the problems of creating local computer networks, there is also the problem of expanding (combining) computer networks. The fact is that a computer network created at a certain stage in the development of an information system may eventually cease to satisfy the needs of all users. In the same time physical properties signal, data channels and design features network components impose severe restrictions on the number of nodes and the geometric dimensions of the network.
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Network hardware To organize a local network, you need to install a network card in each PC and connect all computers using a special cable.
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A network adapter is a device required to connect a computer to a local network. Each network adapter has a unique internal number, the so-called MAC address, which makes it possible to uniquely identify the source of information in the network environment.
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Network boards are characterized by: Bit depth: 8 bits, 16 bits and 32 bits. The data bus through which information is exchanged between motherboard and a network card: ISA, EISA, VL-Bus, PCI, etc. A controller chip on which this board is made. Supported network transmission medium. Operating speed: Ethernet 10Mbit and / or Fast Ethernet 100Mbit, Gigabit Ethernet 1000Base-T. MAC address
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The network adapter is attached to the cable using special connectors, the type of which depends on the type of cable. For example, for a twisted pair cable, an RG-45 type connector is used, which looks like a phone jack. There are network adapters that use the wireless principle of interaction. At present, the three main types of wireless data transmission are radio, microwave, and infrared. The most common, at present, option for organizing a wireless local area network is WiFi usage equipment.
34 slide
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Each network adapter has a unique internal number, the so-called MAC address, which makes it possible to uniquely identify the source of information in the network environment.
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Hardware equipment of computer networks Transmission medium Information can be transmitted using physical signals of various nature. These can be electrical signals, electromagnetic radiation, optical signals. Depending on the type of signal, different transmission media are used - wired or wireless. The transmission medium is a physical medium in which the transmission of information signals in the form of electrical, light and other impulses is possible.
36 slide
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Wireless environment Wired environment In wired environments, computers and other network devices are connected by cables, such as copper (twisted pair, coaxial cable) or fiber optic cables. Data is transmitted in the form of electrical or optical signals. television and radio satellite communications
37 slide
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Coaxial cable - transmission speed up to 10 Mbps Twisted pair - transmission speed up to 100 Mbps Cable types Fiber optic cable - transmission of information over long distances
38 slide
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Network cables Twisted pair cables are one of the components of modern structured cabling systems. It is used in telecommunications and computer networks as a physical signal transmission medium in many technologies such as Ethernet, Arcnet and Token ring. Currently, due to its low cost and ease of installation, it is the most common solution for building wired (cable) local networks.
39 slide
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The simplest design of a coaxial cable includes a copper core enclosed in insulation, a metal shield braid and an outer sheath. In some modifications, an additional layer of foil is present, which means double shielding. The strongest interference is overcome by cables containing four screenings, including two layers of foil and two layers of metal braid. Network cables
40 slide
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fiber optic cable. In a fiber optic cable, digital data is propagated by optical fibers in the form of modulated light pulses. This is a relatively secure transmission method because it does not use electrical signals. So, it is impossible to connect to a fiber optic cable without destroying it and intercept data, which is not immune to any cable that conducts electrical signals. Fiber optic lines are designed to transmit large amounts of data at very high speeds, since the signal in them is practically not attenuated or distorted. An optical fiber is an extremely thin glass cylinder called a core. It is covered with a layer of glass (sheath) with a different refractive index than that of the core. Sometimes optical fiber is made of plastic. Plastic is easier to install, but it transmits light pulses over shorter distances compared to glass fiber. Each fiber only transmits signals in one direction, so the cable consists of two fibers with separate connectors. One of them is for transmitting and the other for receiving. The rigidity of the cable is increased by a plastic coating, and the strength is increased by Kevlar fibers. Network cables
41 slide
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Transmission medium Wireless medium Characteristics of the transmission medium In wireless environments, cables are not used, and data is transmitted over the air, usually in the form of radio signals. One of the main characteristics of the transmission medium is the data transfer rate, which is measured in: bits per second (bps), kilobits per second (Kbps), megabits per second (Mbps) and gigabits per second (Gbps) . The data transfer rate in computer networks is defined as the number of bits transmitted through a certain medium per unit of time.
42 slide
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Wireless connection Uses airborne radio channel; this is convenient as no wiring is required, but more expensive than wired connections Wireless connection
43 slide
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Network interfaces In order for a computer or other device to be connected to a local network, it must be equipped with a network interface (network card) to which a network cable is connected or which will provide communication via a radio channel. Network interfaces are made in the form of boards. A network interface is a piece of equipment designed to connect a computer or other device on a local area network.
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45 slide
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Modems A modem is a device used to connect computers to global networks To connect individual computers and local networks to the global Internet, telephone, cable television networks, and satellite mobile communications can be used. The parameters of the signals transmitted by these communication channels and the signals used in local networks and in the computer itself are different. Therefore, to connect to the global network, a special device is required - a modem. Depending on which communication channel the modem is assigned to, there are modems for telephone lines, television cable lines, satellite modems, modems for mobile communications. Modems are available as stand-alone devices and as boards that plug into slots on the motherboard.
46 slide
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* Modems analog signals digital codes digital codes 101001101 A modem is a device for connecting two computers using a telephone line. Modem (modulator / demodulator) - a device for converting an analog signal into a digital code and vice versa. Exchange rate (bits per second): reception up to 56 Kbps transmission up to 33 Kbps 101001101 modem modem
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48 slide
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Modems Modem CMOTECH High speed wireless modem One of the first usb modems for using mobile Internet.
49 slide
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Modems Thrane Satellite Modem Thrane Explorer 700 TV Cable Modems
50 slide
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Modems Modems for mobile calls Modems for telephone lines
51 slide
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A simple local area network (LAN - Local Area Network) with Internet access consists of network adapters (installed in computers) that are connected to a hub or switch, which in turn is connected to a router. Currently, in the vast majority of cases, Ethernet technology is used to build LAN networks in an office or at home, and twisted pair is used as a network cable.
52 slide
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Hubs, switches, and wireless access points To implement a star network topology, you need a device to which all network computers will connect and which will provide data exchange between them. The function of such "central" devices can be performed by hubs and switches. A hub is a device that transmits received data to all devices connected to it. A switch is a device that determines to whom the received data is addressed, and therefore sends them not to all devices, but only to the recipient. To create wireless networks, wireless access points are used, which function in the same way as hubs.
Teacher: Maybe someone is already familiar with such a concept as computer networks? If yes, how can you explain it.
Students: Maybe it's a connection of computers.
Teacher: Absolutely right. So toA computer network is a system of computers connected by information transmission channels.Let's look at the screen and write this definition in our notebook.
What do you think a computer network is for?
Pupils: To make it easier to work.
Teacher: Right. However, nThe purpose of all computer networks can be expressed in two words: sharing or sharing. First of all, we mean data sharing. People working on the same project have to constantly use the data created by colleagues. Thanks to the network, these and many other problems are solved.
One of the simplest types of connection isdirect connection of computers.
We know that to interact with external devices, computers have special devices - communication ports. With their help, you can not only connect a computer to a printer, or, for example, to a scanner, but also connect two computers to each other - then they can exchange files.Then the simplest computer network is formed, which is called a direct connection.
But a direct connection has three significant drawbacks:
- it allows you to connect up to 2 computers
- throughput is low
- the length of the direct connection is extremely small (up to 1.5 m for parallel and up to 10 m for serial connection)
Network adapters are used to create more complex connections. If a network adapter is installed on the computer, a so-called network port is formed on it. By connecting the network ports of different computers with each other using cables, computer networks are obtained.
Types of computer networks.
By geographical principle, local and global networks are distinguished.Local area networks unite computers located at a short distance from each other. Global networks can cover vast territories comparable to the size of a state.
Local networks, their main properties.
These networks are small in scale and operate within the same premises, building, enterprise. They are united by a relatively small number of computers (up to 1000 pieces).
Typically, computers on the same local network are separated from each other by a distance of no more than one kilometer.
The use of a local network serves two main purposes:
- Sharing files between network users
- Use of public resources: large disk space, printers, programs, etc.
Basic properties:
- High transmission speed, large bandwidth;
- Low level of transmission errors;
- A precisely defined number of computers connected to the network;
- Has one or more interconnected control centers.
The last parameter, in essence, determines that this is a local network. For example, HP has one of the largest local area networks, whose computers are distributed all over the world. The main difference between such a network and a global one is the presence single center management, which is fundamentally absent in global networks.
LS organization.
From the point of view of organizing the interaction of individual elements in a LAN, two types are distinguished:
1. Peer-to-peer network
All connected computers are equal. The user can access the resources of all computers connected to him. Do not need special software. Peer-to-peer networking is supported by Windows95/98/00.
2. Network with a dedicated file server (main computer).
It is also called a client-server network.. There is one central machine, which is called the server, and many computers connected to it - workstations or clients. The central machine is usually a more powerful machine (it has a large disk memory, a printer, scanner, modem, etc. are connected to it. Direct information is exchanged between the server and the workstation. Of course, in such a system, students can also exchange files, but "transit" through server.
The name "server" comes from the English. and translates as a service device.The server plays the role of a collective storage of files.
The operation of such a network is controlled by the network operating system. Its main purpose is to enable users to work in a LAN without interfering with each other. The most common operating systems for networks with a dedicated server are NOVELL NETWARE, WINDOWS NT.
Topology.
RING: Each computer is connected to each other. Signal, carrying information goes in circles.
BUS: Computers connected in series. All computers are connected to the same cable. The main disadvantage is that a cable break at any point breaks the network.
STAR: Uses a separate cable for each computer, routed from the central device (hub, HUB). More resistant to various cable damage.
SNOWFLAKE: A variation of the "Star". There is one central server for the entire network and several file servers for different workgroups.
Network hardware.
To organize communication, computers were originally connected by coaxial cable. Recently, however, twisted-pair cable, used in laying telephone lines, has become popular. With the decrease in cost, fiber optic cable is also gaining popularity. Along with this, there are cableless network solutions using radio waves, infrared radiation, etc.
The main parameters of communication lines is the bandwidth ( maximum speed transmission of information), noise immunity, cost. Let's write down the relative characteristics of communication lines (see Appendix 1).
Let's try to put our knowledge into practice. What kind of network do we have in the audience?
Students: Local.
Teacher: Right. And why?
Pupils: Because we can transfer information from one computer to any other and we are located within the same building.
Teacher: And what type of network: peer-to-peer or with a dedicated server, will we classify our network?
Students: Peer-to-peer! With a dedicated server!
Teacher: So, opinions are divided. How to define it? Remember we had lessons when the "master machine" was not even turned on, and you were working at your computers. Could this be the case if this machine was a server? Of course not. So it's a peer-to-peer network. Topology?
Students: Star.
Teacher: How did you determine so quickly and correctly?
Pupils: Because there is a HUB. (The teacher previously, when he explained about the HUB, showed them an example)
Teacher: That's right.
Teacher : I propose to organize 4 groups for the next task. Each group will describe their own version of building a network in a new computer room, make an approximate cost calculation, and justify the advantages and disadvantages of their own version.
So, today we have learned what computer networks are and what they are for, their two main types. We got acquainted with local networks, their organizations and topologies in more detail. In addition, we learned to apply our knowledge in practice.
Your homework will be to know the material in this lesson. In the next lesson, I will ask you, and then we will continue to study this topic, find out how global networks are organized.
And now the lesson is over. Goodbye! You can be free.
Combining computers into a local area network
A local area network (LAN) is a combination of hardware and software that allows you to combine computers into a single distributed system for processing and storing information.
Two computers can be connected with a piece of cable connected to their parallel ports. In this case, no additional hardware and software for such a "network" is required. All the software needed to manage the connection is already in the operating system. With such a connection, one of the computers is assigned as the master, and the other as the slave. From the host computer, you can access all drives and folders on the slave computer that are allowed to be shared. This connection of computers in a network is called a direct connection. To connect more than two computers, a direct connection is not enough. In this case, you need to install a network card in each computer, connect them with cables, and run special programs that control how computers work together. Some networks have a dedicated control computer called a file server. All "regular" computers in such a network are called workstations.
A LAN can include a variety of independent devices: large, small and micro computers, terminals and terminal stations, various peripheral equipment, magnetic tape and disk drives, as well as specialized tools (copiers, plotters, communication devices with objects, etc. .).
The local area network implements the following functions:
1) A wide variety of digital information can be transmitted over a local network: data, images, telephone conversations, emails, etc.
2) Most often, local networks are used to share (that is, share) resources such as disk space, printers, and access to the global network.
3) LANs allow the exchange of information between computers different types. Network subscribers can be not only computers, but also other devices, such as printers, plotters, scanners.
4) Local networks make it possible to organize a system of parallel computing on all computers in the network, which makes it possible to speed up the solution of complex mathematical problems many times over. They can also be used to control the operation of a complex technological system or a research facility from several computers simultaneously.
5) Organizing paperwork, controlling access to information, protecting information. LAN allows you to implement a unified security policy in the enterprise, you can always clearly define access rights to documents and record the actions of employees.
Local area network hardware includes computers with network adapters installed on them, repeaters, hubs, switches, bridges, routers, etc., connected to each other using a cable system or wirelessly.
TO software can be attributed to network OS, system and application programs used for network interaction corresponding transmission protocols.
Peer-to-peer and client-server networks can be distinguished.
In peer-to-peer LANs, all workplaces (computers) have the same capabilities in relation to each other. There is no separation of functions, and computers are simply connected to each other in working group to share files, printers, and Internet access. This is common for workgroups with 10 or fewer computers.
In the client-server model of the user's PC (client) acts as a request source machine, and a more powerful machine (server) is endowed with dispatching functions. This computer typically has the highest performance, communicates over a LAN or WAN, acts as a request service system by managing hard drives, supports shared peripherals such as printers, plotters, streamers, scanners, modems, etc. P.
A server is a computer on a network that provides its services to others, that is, it performs certain functions at the request of others. A server is also a program for a network computer that serves many network clients.
There can be several servers in the network, and it is not at all necessary that the server is the most powerful computer. A dedicated server is a server that deals only with network tasks. A non-dedicated server can be engaged in other tasks besides network maintenance. specific type server is a network printer.
A client is a network subscriber who only uses network resources, but does not give his own resources to the network, that is, the network serves him. The client computer is also often referred to as a workstation. In principle, each computer can be both a client and a server at the same time.
Server and client are also often understood not as computers themselves, but as software applications running on them. In this case, the application that only sends the resource to the network is the server, and the application that only uses the network resources is the client.
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