The concept of a local area network (LAN). Local network - what is it and why is it needed? How lvs stands for

The very name of the Local Area Network already contains the purpose, functions and limitations of the system. Let's break down the name into its components. Local, formed from the English local - local, that is, the network is tied to a specific geographic place and has territorial restrictions, computing, is associated with the composition of the network (computing equipment, software) and its purpose, network- implies the integration of computing equipment and software in a certain area (local) into a network (by means of cables).

Thus, we can formulate the definition of a Local Area Network (LAN) - a system of interconnected computing resources (computers, servers, routers, software, etc.), distributed over a relatively small area (office or group of buildings), serving for reception and transmission, storage and processing of information of various kinds.

Different local area networks can function separately or be interconnected by means of communications, for example, in enterprises with a branch network in different cities. Thanks to this connection, the user can interact with other workstations connected to this local area network. There are local networks, the nodes of which are geographically dispersed over distances of more than 12,500 km (space stations and orbital centers), but they are still classified as local.

The purpose of a LAN is to provide joint and simultaneous access of a certain group of persons to data, programs and equipment (computers, printers, plotters, storage and processing devices for files and databases) and data transmission (electronic graphics, word processing, e-mail, access to remote databases data transmission, digital voice transmission).

For example: a manager accepts an order and enters it into a computer, then the order goes to the accounting department and an invoice is formed there, at the same time information can come to the legal service to create an agreement.

LAN characteristics:

• High-speed channels (1-400 Mbit / s), belonging mainly to one user;
• The distance between workstations connected to a local network usually ranges from several hundred to several thousand meters;
• Data transfer between stations of computer users;
• Decentralization of terminal equipment, such as microprocessors, displays, cash registers, etc.
• Data transmission to subscribers connected to the network via a common cable;

The main functions of a LAN are:

• Providing simultaneous access to networked equipment, software and information;
• Minimizing the risk of unauthorized access to information and network resources;
• Differentiation of access to information and network resources;
• Ensuring fast and confidential exchange and simultaneous work with information for a certain circle of people;
• Control over information flows, including incoming and outgoing;
• Delineation of control functions and responsible persons at each node (for each node is responsible System Administrator performing service and, as a rule, control functions);
• Optimization of costs for software and equipment due to their collective use (for example, one printer for several departments, etc.)

As a result of the use of LANs, personal computers located in many remote workplaces. Workplaces of employees are no longer isolated and are consolidated into unified system which has its own special Benefits:

• Possibility remote access to hardware, software and information;
• Optimization of processor resources;
• Less number and rate of errors compared to a network based on telephone channels;
• The bandwidth is higher than that of the global network;
• Possibility of reconfiguration and development by connecting new terminals

Application area local area networks are very wide, currently there are such systems in almost every office (for example, one printer is installed on several computers, or several computers use one software, for example, 1C: Accounting, etc.). Every day, the flows of information are growing, the software used is more complex and functional, the geography of the activities of organizations is expanding. The use of LAN facilities becomes not only desirable, but necessary for the successful operation and development of business, science, teaching students, schoolchildren, training and retraining specialists, performing government programs and functions, etc.

The structure of the network functioning.

The structure of a local network is determined by the management principle and the type of communication; it is often based on the structure of the organization served. Types of topology are used: bus, ring, radial, tree. The first two types are most common, due to effective use communication channels, ease of management, flexible expansion and change options.

Bus topology- all computers are connected in a chain by connecting to a trunk cable segment (trunk), terminators are placed at its ends to damp the signal propagating in both directions. The computers on the network are connected by a coaxial cable with a tee connector. Network bandwidth - 10 Mbit / s, for modern applications actively using video and multimedia data, this is not enough. The advantage of this topology is low wiring costs and unified connections.

The bus topology is passive. Failure of one computer does not affect network performance. Damage to the backbone cable (bus) leads to signal reflection and the entire network becomes inoperative. Switching off and especially connecting to such a network requires a bus break, which disrupts the circulating flow of information and freezes the system.

Tree topology- a more advanced configuration of the "bus" type. Several simple buses are connected to a common backbone bus through active repeaters or passive multipliers.

Star topology(star) - is the fastest of all topologies, information between peripheral workstations passes through the central node of the computer network. Central control node - the file server can implement an optimal protection mechanism against unauthorized access to information. The entire computer network can be controlled from its center.

The cable connection is fairly straightforward as each workstation is only connected to the central site. The cost of cabling is quite high, especially when the central site is not geographically located at the center of the topology. When expanding computer networks, the previously made cable connections cannot be used: a separate cable must be laid to the new workplace from the center of the network.

In the case of a serial LAN configuration, each device connected to physical environment transmits information to only one device. This reduces the requirements for transmitters and receivers, since all stations actively participate in the transmission.

Ring topology(ring) - computers are connected by segments of a ring-shaped cable, essentially identical to the bus cable, with the exception of the need to use "terminators". In the event of a malfunction of one of the network segments, the entire network fails.

Signals are transmitted in one direction only. Each station is directly connected to two neighboring ones, but listens to the transmission of any station. The ring is made up of several transceivers and the physical medium connecting them. All stations can have equal access rights to the physical medium. In this case, one of the stations can act as an active monitor serving the exchange of information. Routing cables from one workstation to another can be quite difficult and expensive, especially if the workstations are geographically located far from the ring (for example, in a line).

The main problem with a ring topology is that each workstation must actively participate in the transfer of information, and if at least one of them fails, the entire network is paralyzed. Faults in cable connections are easily localized. Connecting a new workstation requires turning off the network, since the ring must be open during installation. There is no limit to the length of a computer network, since it is ultimately determined solely by the distance between two workstations.

Computers can be connected to each other using various access media: copper conductors (twisted pair), optical conductors (optical cables) and through a radio channel (wireless technologies). Wired, optical connections are established via Ethernet, wireless - via Wi-Fi, Bluetooth, GPRS and other means. Most often, local networks are built on Ethernet or Wi-Fi technologies. It should be noted that Frame Relay and Token ring protocols were previously used, which today are increasingly rare, they can be seen only in specialized laboratories, educational institutions and services.

Components for building a simple local network are used:

• Adapter (network adapter) - a device that connects a computer (terminal) with a network segment;
• Bridge (bridge) - a device that connects local or remote network segments;
• Router (router) - a device for limiting broadcast traffic by dividing the network into segments, ensuring the protection of information, managing and organizing backup paths between broadcast areas;
• The switch is a narrow-purpose device that effectively segments the network, reduces collision areas and increases throughput each terminal station.
• Blocks uninterruptible power supply- devices for ensuring the operability of the system in cases of disconnection of the main power source.

Installation of Local Area Network (LAN)

The choice of the type of topology, access environment and composition of the Local Computer System depends on the requirements and needs of the Customer. Modern technologies allow you to develop an individual option that meets all the requirements and tasks.

Laying LAN cables, like other types of cable networks, can be carried out different ways... When choosing a method of installation, they are guided by the individual architectural and design features of the building, its technical characteristics, the presence of operating networks and other equipment, the order of interaction of low-current systems with other systems. In principle, two methods can be distinguished - open and hidden. For hidden wiring of LAN cables, the construction of walls, floors, ceilings is used, it looks more aesthetically pleasing, the routes are protected from extraneous influences, access to them is limited, the laying is done immediately in specially prepared places, and the best conditions for subsequent maintenance are provided. Unfortunately, the opportunity to perform work in a hidden way is rare, more often you have to carry out work open way using plastic boxes, vertical columns and trays. Do not forget that there is also a way to lay cables through the air, most often it is used for communication of buildings when it is not possible to lay the cable into channels or if it is too expensive.

Installation of a LAN is a difficult and responsible job. , the quality of its implementation depends on the stability and correctness of the functioning of the system as a whole, the degree of fulfillment of the tasks assigned to it, the speed of data transmission and processing, the number of errors, and other factors. This must be treated very thoroughly and seriously, since any network is the basis (skeleton and circulatory system) of the whole organism from low-current systems responsible for a large number of functions (from Email to the safety of the object). Each subsequent intervention in the operation of the existing system (expansion, repair, etc.) requires time and money, and their number directly depends on the parameters originally laid down in the system, the quality of the work performed, the qualifications of developers and performers. Saving money at the stage of designing and installing a LAN can turn into much higher expenses at the stage of operation and upgrade

A local computer network is also called a local computer network, since it serves to unite network devices into a small group. The interconnection of network devices can be carried out not only using cables, but also using wireless technologies.

Purpose of LAN

Consolidation of network devices is its main purpose. With the help of a LAN, users can exchange data, connect to shared printers and print documents, store data on a shared server or on their computer, with the ability to access them by other LAN users.

LAN volume

Typically, a local area network extends to an office, home, premises or building. A LAN can even connect several buildings, however, if you use a twisted pair cable to connect buildings, the distance (cable length) should not exceed 100 meters. Otherwise, data transmission delays may occur. Twisted pair rarely hesitate to connect two or more buildings into one LAN. Most often, an optical cable and associated equipment are used to accomplish this task.

LAN types

Peer-to-peer LAN

A peer-to-peer local area network is used to connect a small number of computers (up to 10 pieces). In a peer-to-peer local area network, each user of his computer makes a decision about access to data for other users of the network. This LAN is also called peer-to-peer.

The local network server based

This is a more widespread type of LAN, more efficient and reliable. The server can serve as regular computer, and special, whose features and software are designed specifically for these purposes. The server can perform a lot of functions: store the data of LAN users, assign rights and restrict access to users, determine optimal routes when sending messages, and much more.

LAN topology / structure

The topology of a local area network determines the structure of how computers will connect to each other.

1. Bus is a serial connection of computers to a network using a common cable.

2. Star is a parallel connection of computers. Each computer is connected with a cable to one device - a hub or hub.

3. Ring- computers are connected by a cable in an inseparable ring. Failure of any computer or cable break - will lead to inoperability of the LAN.

V modern world LANs have become more than just necessary - they are actually necessary to achieve good levels of productivity. However, before you can start using such a network, you must create and configure it. Both of these processes are quite difficult and require maximum concentration, especially the first one. An improperly designed and configured LAN will not work at all, or it will function completely differently, so the creation of a local network should become the focus of the person doing this.

What is a local network

Typically creating similar systems communication is caused by the need for collective use of data by users who work on remote computers. LAN not only allows for almost instant information exchange and simultaneous work with files, but also allows you to use network printers and other devices remotely.

A local network is a full range of software and hardware resources aimed at creating a single information space... In fact, this is a number of computers located at a distance from each other and connected by a communication line - a cable. The main difference between a LAN and other types of networks is short distance where the workstations are located.

Pre-project preparation and design

Before creating a local network, you must first design it, that is, plan the process of its creation. This stage is one of the most significant, since the LAN includes great amount components and assemblies.

Initially, a technical assignment is drawn up on the basis of primary data, identifying several points:

• Functions and tasks of the LAN.
• Selected topology.
• List of available equipment.

Only after deciding on these points, you can start designing. The project itself should contain LAN diagrams, points of arrangement of network equipment, a list of required software and hardware.

The local network is complex mechanism, but if it is designed correctly, and the equipment is selected in accordance with the requirements, in this case, the likelihood of problems in the operation of the communication mechanism becomes minimal.

Required hardware

There is a list of equipment without which no LAN can function. It includes:

• Data transmission lines. Most commonly used coaxial cable and fiber optic. At the same time, the length of the coaxial cannot exceed several hundred meters, however, if it is necessary to extend the network over long distances, special repeaters are used - signal repeaters that do not allow it to fade.
• Communication equipment: network cards (devices that perform duplex exchange of information between a computer and a data transmission medium), hubs (divide the network into separate segments, structuring the network physically), routers (take on the choice of the packet transmission route), switches (logically divide the LAN into segments, combining several physical circuits), repeaters (provide signal recovery, allowing you to increase the length of the transmission medium), transceivers (amplify the signal and convert it into other types, allowing you to use different data transmission media).

List of software tools

No LAN is complete without software... Must-have programs for a local area network include:

• Operating systems of worker nodes. The most frequently used operating system remains Windows 7, although Windows XP is not losing ground either.
• Network operating systems installed on servers are the basis of a LAN, since it is impossible to configure a local network without them. Exactly these software take control of all data flows between the main nodes and the secondary nodes, providing the ability to share network resources. As a rule, the operating systems of Microsoft Corporation are used: Windows Server 2003 or 2008.

• Network services and applications that provide users with the ability to access deleted files, printing documents on a network printer, viewing work nodes located on the network, as well as sending e-mails... These services are implemented using software.

Creation and installation of a LAN

Installation and commissioning work takes the most time, since a local network will have to be created in several stages:

• Before starting the installation of communication lines and switching devices, you must first prepare the room.
• Further, you can carry out the laying of the cable, as well as the installation of the necessary equipment.
• The server and workstation devices should be connected to the cable communication line.
• After that, the software is installed and configured.

Installation of cable and equipment has a number of features, therefore, if there are difficulties with how to connect a local network, better solution entrust this issue to specialists.

Connecting two computers on a LAN

In some cases, it may be necessary to combine two computers into one network, for example, to create a common information space. This is not very difficult to do if you follow a certain algorithm of actions:

• If necessary, install network adapters in both computers, not forgetting about the drivers.

• Purchase a crimped network cable for connection. If you have the necessary knowledge and skills, crimping can be done on your own - the local network of two computers will not become the worst quality from this.
• Connect both workstations with a communication line.
• Configure the LAN in a specific order.

Algorithm for setting up a local network between two computers for Windows 7

• Select the "Start" menu, then, by right-clicking on the "Computer" icon, enter the "Properties" submenu.
• You need to find in the list "Computer and domain name", and then select the item with changing the settings.
• The working name of the computer must be changed by clicking on the corresponding icons.
• The group name should remain unchanged - "Workgroup", but the computer names are changed to "pc1" and "pc2" for the first and second subscribers, respectively.
• Now you can click OK and restart your computer.

In most cases, you may need to assign each host an individual IP address:

• From the Start menu, select Settings and then Network Connections.
• Right-click to bring up the "Properties" submenu next to the "Local Area Connection" icon.
• In the "General" tab, select "Properties" of the "Internet Protocol" item.
• Make active the line "Use the following IP address" and enter the value 192.168.0.100. Then save the changes made.

Local network and Internet

Work nodes connected to a LAN can be connected to the Internet. A local network, the Internet to which can be connected in two ways, will work at halved speed.

The first way to connect is to use a router that is assigned an identification IP address. And in the second case, you can use a wireless connection.

In this case, a local network is the interaction of two computers, a master and a slave, so the IP address is registered in the gateway of the main one, which is previously connected to the world network.

If the LAN is based on the use of a server, each workstation must have an individual IP address, and the proxy server through which the Internet is accessed is indicated in the browser settings.

Wireless LAN

A wireless local area network (WLAN) is a subset of a LAN that uses high-frequency radio waves to transmit information. WLAN is an excellent alternative to conventional wired communication, offering a number of advantages:

• Improving labor productivity. WLAN makes it possible to use the Internet without being tied to one room. You can freely change your location without losing your internet connection.
• Easy installation and setup, financial savings and reliability - all these factors are due to the absence of a cable communication line.
• Flexibility. Wireless network installation is real where there is no way to stretch the cable.
• Expandability. Network scalability is greatly simplified with wireless network adapters that can be installed on any work node.

WLANs have a certain range, which depends on the characteristics of the network devices and the noise immunity of the building. Typically, the range of radio waves reaches 160 m.

Equipment Needed to Create a Wireless LAN

An access point is used to connect other workstations to the network. This device is equipped with a special antenna that controls the duplex transmission of data (send and receive) using radio signals. Such a point can transmit a signal at a distance of up to 100 m indoors and up to 50 km in an open area.

Access points significantly expand computing power the entire communication system, allowing users to move freely between each of them without losing their connection to the LAN or the Internet. In fact, these radio points act as hubs, providing a connection to the network.

Using access points allows you to scale up your entire WLAN by simply adding new devices. The number of subscribers that one radio point can withstand generally depends on the network congestion, since the traffic is divided equally between each of the users.

Wireless LAN: Windows 7. Configuration Algorithm

First you need to prepare an ADSL modem with WiFi technology, as well as the client points connected to them wireless adapters... After that, you can start building a wireless LAN:

• Connect the modem to the electrical network.
• Launch the WLAN setup wizard on the client device.
• Select the SSID from the list of found wireless networks.

Access point setting:

• The first step is to configure the TCP / IP properties by specifying the IP address and subnet mask.
• After that, specify the value DNS server, since it is not possible to fully configure the local network without this parameter. In most cases, it is enough to make active the item on the automatic assignment of the DNS address.
• It is also mandatory to configure the parameters of the wireless network itself, in which security is important.
• At this stage, you need to configure an Internet connection and filtering for the Windows 7 firewall.
• And the last thing is to connect the wires and check the functionality of the WLAN network.

To create an optimal information space, you can combine the types of networks - cable and wireless, allowing you to take advantage of each of them for the benefit of the enterprise. However, it is important to remember that in our time it is more and more used wireless networks WLANs that have all the benefits of wired networks without their drawbacks.

After completing the creation and configuration of the local network, it is important to provide for its administration and the possibility Maintenance... Even if the LAN installation is perfect, it is almost inevitable that various hardware or software malfunctions occur during its operation, which is why maintenance must be carried out on a regular basis.

By tradition, the first cat is launched into the house. For organizations, the role of a "cat" is sometimes played by a local area network. Without it, a rare company will start working in a new office.

Installation of a LAN (Local Area Network, or LAN, that is, Local Area Network - a prerequisite for effective work a modern company that cannot do without computers and other electronic devices.

But what is a LAN? A white cord that runs along the walls and plugs into your computer? You might be surprised to learn how much is included in the concept of a local area network.

What is a local area network?

LAN is a set of software and hardware for combining computers into a single system for storing and processing information. To put it simply, a local network is everything: computers, modems, servers, routers, switches and other equipment. This is on the one hand. With another - OS and network protocols.

The word "local" in a LAN name indicates the size of the network. Usually it serves to unite one office or building. More rarely, several houses.

The distance between computers in the local network should not exceed 100 meters. This is due to the fact that the electrical signal cannot travel long distances through the cable. This limitation can be combated. For this, active network equipment is placed between the computers.

What is a LAN for?

Here are the main tasks that are solved thanks to the local area network:

• General access in Internet... Thanks to the installation of a local network in the office, you can easily organize an Internet connection for each employee.
• Communicative... Thanks to the local network, you can configure mail server and organize a mail server or install an exchange program instant messaging.
• Collaboration... Employees can collaborate on documents on the server without creating duplicates or hard copies. The work is going much faster and more organized.
• Sharing printers, copiers and scanners. You can significantly save on cost Supplies by acquiring network printer or a scanner.
• The network opens up huge prospects for the organization of office work. For example, you can use the Corporate information system(CIS).

No, these are far from all the possibilities of the network, but the above is enough to understand how powerful a tool a well-planned and configured local network can become.

197110, St. Petersburg, Maly Prospekt PS, 4

+7 (812) 235-17-75, 235-67-14, E-mail: [email protected] www.apc.simetaplus.ru

What is the difference between SCS and Local Area Networks (LAN)?

LAN is computer network, built on the basis of the requirements of one technology that will be used in a given network, most often it is Ethernet and it covers only computers. The main difference between SCS and LAN is its independence from the applications that will be used later, which allows it to support a wide range of applications.

SCS is a broader concept than a LAN, since it covers the transfer of information from a wide range of tasks, such as the transmission of voice, data and video images, thereby allowing integration into a single information structure computer and telephone network, fire and burglar alarms, video surveillance, television, radio, etc. A properly constructed SCS is a reliable and flexible structure with advanced tools for its management, monitoring and expansion.

SCS allows you to quickly and easily change the configuration of the cable system without changing its capital basis.

The advantages of structured cabling systems over conventional ones:

• for data, voice and video transmission, a single cable system(transmission medium);
• long service life that justifies the investment;
• modularity and the ability to change the configuration and expand without replacing the entire existing network;
• allow the simultaneous use of several different network protocols;
• do not depend on changes in technology and equipment supplier;
• use standard components and materials (copper unshielded and shielded twisted cable, fiber optic cable);
• allow the management and administration of a minimum number of service personnel;
• allow combining fiber-optic and copper cables in one network.
• reduction in the cost and time of installation of systems, since the laying of the entire cable infrastructure can be carried out by one, rather than several companies.

Design and installation of SCS are carried out in accordance with the international standard ISO / IEC 11801. The department implements a quality management system for certification for compliance state standard DSTU ISO 9001-2001.

Works are carried out using high quality AMP, R&M components. We carry out 100% testing and certification of the objects being handed over with the provision of a component or system guarantee from manufacturers of passive equipment (15-25 years).