A local area network is also called a local area network, as it serves to connect network devices into a small group. Connecting network devices can be done not only using cables, but also using wireless technologies.

LAN purpose

Consolidating network devices is its main purpose. Using a LAN, users can exchange data, connect to shared printers and print documents, store data on a common server or on their computer, with the ability for other LAN users to access it.

LAN volume

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

Types of LAN

Peer-to-peer local network

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

Server based local network

This is a more common type of LAN, more productive and reliable. The server can be either a regular computer or a special one, the characteristics and software of which are designed specifically for these purposes. The server can perform a lot of functions: store LAN user data, assign rights and limit access to users, determine optimal routes when transmitting 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. Tire- This is a serial connection of computers into a network using a common cable.

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

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

LAN (local area network) is a system for connecting various telecommunication devices located both in close proximity and remotely. A LAN can connect several personal computers, servers, printers, scanners, etc. into one network.

Devices communicate using various means of access: copper cable (twisted pair), fiber optic cable or wireless channel communications.

Sometimes work groups are created within the same local network, uniting several devices under a common name.

Most often, a LAN is used to create a single information space in various government and commercial organizations. Network administrators are responsible for the operation of the local network or a certain part of it. They ensure stable operation of the network, configure equipment and software.

LAN functions

1.Providing access to electronic document management systems and the Internet.

2. Providing public access and sharing of files and folders on the network.

3. Data storage, backup and protection.

4. Providing access to multiple computers for office equipment, such as a printer or scanner.

5. Networking of devices located at a considerable distance from each other. For example, a LAN can unite geographically dispersed branches of one company.

Connecting devices on a LAN

Computers can be connected to each other either using a cable system or wirelessly. In the first case, the devices are connected using copper or fiber optic conductors and Ethernet packet data transfer technology.

If the conductor is a wireless radio channel, then technologies such as GPRS, Wi-Fi, and Bluetooth are used. One local network can connect to another through gateways, and also have access to global network Internet.

The most popular technologies for building local networks today are Wi-Fi and Ethernet. To build a LAN, devices such as wireless access points, routers, network adapters, switches, modems, etc.

LAN properties

Firstly, a local area network allows you to connect additional equipment without changing the software and technical parameters of the entire network. Secondly, if one computer fails, the entire network continues to work, and access to the necessary information can still be obtained. Thus, due to technical problems of one device, the work of the entire office will not stop. In addition, thanks to the LAN, you can differentiate the level of access to network resources individual devices.

LAN structures

The LAN structure refers to the method of connecting network elements. Here are the main types of such connections.

1. "Tire". Information is transmitted over a single linear communication channel. Data is available to all workstations on the network.

2. "Star". Using a coaxial cable, all network elements are connected to one concentrating device (hub). Information from one workstation goes to the hub, and from there it becomes publicly available to all other computers.

3. "Ring". Computers on the network are connected to each other in series and form a ring. Information flows in a circle from the first workstation to the last.

4. Tree structure is a combination of two or all of the above communication methods.

LAN is a technology that provides convenient and fast exchange of information between several devices. Using local networks, you can store, backup and protect data. Therefore, LANs are now available in almost all offices of companies, banks and industrial enterprises.

LAN SCS and fiber optic lines. Correlation and mutual difference. Concept and general description

To understand the relationship between SCS LANs (local area networks and structured cable networks), you should know about this type of network as fiber optic lines. A fiber-optic transmission line or fiber-optic communication line, traditionally called by the abbreviation FOCL, is a communication channel (line) that transmits information through optical fiber, a special material that differs from others in its extremely low degree of signal attenuation over a distance. This property of fiber optics allows it to be used in backbone networks to transmit data over vast distances.

SCS stands for structured cabling system. The information structure of the entire company is as effective as the SCS is organized correctly. SCS as a complex of numerous elements includes the following elements

• LAN (local computer network);
• video surveillance systems, alarm systems, other security systems;
• engineering infrastructure and other low-current networks

A local area network (LAN) as part of an SCS is used to transmit, process and store data within a certain space (enterprise, division, office). A properly prepared LAN project within the framework of SCS, properly implemented, provides high network throughput in conjunction with the ability to control data, manage network access and centralize remote control connected equipment.

So, if we arrange the above-described types of networks in order of their scale, we will get the following picture - an extended and large-scale fiber-optic line is connected to an enterprise SCS, which, in turn, includes a LAN.

Subsequent installation of LAN SCS and fiber optic lines. Stages of creating networks.

Both fiber-optic lines, SCS, and LAN are designed and created on the basis of common principles. The process of constructing each type of network can be divided into two large stages - design and installation of SCS, LAN or fiber optic lines. Let's look at them in order.

1. Design. The design of a system, be it SCS or LAN, contains an explanatory note, documentation, technical and graphic parts, and a package of permits.

The explanatory note drawn up when designing a fiber-optic line, structured cabling system or LAN contains a general description and characteristics of the object as a whole, defines its purpose, establishes general technical requirements related to the installation of the network.

The cable log, which contains a numbered inventory of all cables, ports and sockets that make up the network, is the main working document.

The technical part is primarily equipment specifications, and the graphic part is various diagrams and floor plans.

1. Installation of SCS or other cable systems. Upon preparation of the project, based on the content of the working documentation, specific work is carried out to install the designed network. Initially, this may be preliminary work - construction, land. The object (building, structure, as well as land) is prepared for the installation of a LAN SCS or fiber-optic line - land channels are dug, cable channels are laid, holes are drilled.

Then the installation and installation of cables takes place, technical devices, setup is in progress. Commissioning is in progress.

Evidence and documentary evidence of a high-quality and fully completed process of creating a fiber-optic network, SCS or LAN is a protocol signed by the customer and the contractor. Only experienced and highly qualified specialists in the field of design and installation of SCS and other cable networks can guarantee a high level of quality of network construction, stable and efficient operation.

According to tradition, the cat is the first to be let into the house. For organizations, the role of “cat” is sometimes played by a local area network. Without it, a rare company will start work in a new office.

Installation of a LAN (Local Area Network, or LAN, that is, Local Area Network is a necessary condition for efficient work a modern company in which one cannot do without computers and other electronic devices.

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

What is a local area network?

A 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 the name of a LAN indicates the size of the network. Usually it serves to unite one office or building. Less often - several houses.

The distance between computers on the local network should not exceed 100 meters. This is due to the fact that electrical signal cannot travel long distances via cable. This limitation can be overcome. To do this, active network equipment is installed between computers.

What is a LAN for?

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

• General access in Internet. Thanks to the installation of a local network in the office, it is possible to organize an Internet connection for each employee without any special expenses.
• Communicative. Thanks to the local network, you can configure mail server and organize a mail server or install an instant messaging program.
• Collaboration. Employees can collaborate on documents on the server without creating duplicates or hard copies. The work goes much faster and more organized.
• Sharing access to printers, copiers and scanners. You can save a lot on cost Supplies, having purchased network printer or scanner.
• The network opens up enormous prospects for organizing office work. For example, you can use Corporate information system(CIS).

No, this is not all the capabilities of the network, but what is listed is enough to understand what a powerful tool a well-planned and configured local network can become.

The very name Local Area Network already contains the purpose, functions and limitations of the system. Let's break down the name into its components. Local, derived from the English local - local, that is, the network is tied to a specific geographical location and has restrictions on the territory, computing, is associated with the composition of the network (computing equipment, software) and its purpose, net– implies the integration of computing equipment and software in a certain territory (local) into a network (via cables).

In this way, 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), used for reception, transmission, storage and processing information of various kinds.

Different local area networks can operate separately or be interconnected using communications means, 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 whose nodes are geographically separated over distances of more than 12,500 km (space stations and orbital centers), but they are still classified as local.

The purpose of the LAN is to ensure shared and simultaneous access of a certain group of people to data, programs and equipment (computers, printers, plotters, storage and processing devices for files and databases) and data transfer (electronic graphics, word processing, e-mail, access to remote databases data, digital speech transmission).

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

LAN characteristics:

• High-speed channels (1-400 Mbit/s), owned primarily by one user;
• The distance between workstations connected to the local network is usually from several hundred to several thousand meters;
• Data transfer between computer user stations;
• Decentralization of terminal equipment, which uses microprocessors, displays, cash register devices, etc.
• Transferring data to subscribers connected to the network via a common cable;

The main functions of the LAN are:

• Providing simultaneous access to equipment, software and information integrated into a network;
• Minimizing the risk of unauthorized access to information and network resources;
• Restriction 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;
• Separation of control functions and responsible persons at each node (a system administrator is responsible for each node, performing maintenance 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 application, LANs are united personal computers, located at many remote workplaces. Employees' workplaces cease to be isolated and are combined into a single system, which has its own special advantages:

• Opportunity remote access to equipment, software and information;
• Optimizing processor resources;
• Less number and intensity of errors compared to a network based on telephone channels;
• Bandwidth is higher than that of the global network;
• Possibility of reconfiguration and development by connecting new terminals

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

Network functioning structure.

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

Bus topology– all computers are connected in a chain by connecting to the backbone cable segment (trunk), with “terminators” placed at its ends to dampen the signal propagating in both directions. Computers on the network are connected by a coaxial cable with a tee connector. The network bandwidth is 10 Mbit/s, which is not enough for modern applications that actively use video and multimedia data. The advantage of this topology is the low cost of wiring and unification of connections.

The bus topology is passive. The failure of one computer does not affect the functionality of the network. Damage to the backbone cable (bus) leads to signal reflection and the entire network as a whole becomes inoperable. Shutting down and especially connecting to such a network requires a bus break, which disrupts the circulating flow of information and causes the system to freeze.

Tree topology– a more developed “bus” type configuration. 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. The central control node - the file server can implement the optimal protection mechanism against unauthorized access to information. The entire computer network can be controlled from its center.

Cabling is fairly simple as each workstation is only connected to the central hub. Cabling costs are quite high, especially when the central node is not geographically located in the center of the topology. When expanding computer networks, previously made cable connections cannot be used: a separate cable must be laid from the center of the network to the new workplace.

In the case of a sequential LAN configuration, each device connecting to the physical medium transmits information to only one device. At the same time, the requirements for transmitters and receivers are reduced, since all stations actively participate in the transmission.

Ring topology(ring) – computers are connected by segments of a ring-shaped cable, fundamentally identical to a bus, with the exception of the need to use “terminators”. If one of the network segments fails, the entire network goes down.

Signals are transmitted in one direction only. Each station is directly connected to its two neighbors, but listens to the transmission of either station. The ring consists of several transceivers and the physical environment 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 information exchange. Laying cables from one workstation to another can be quite complex 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 on 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 and 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 are becoming less common today; they can only be seen in specialized laboratories, educational institutions and services.

Components of building a simple local network are used:

• Adapter (network adapter) – a device that connects a computer (terminal) to a network segment;
• Bridge – a device connecting local or remote network segments;
• Router – a device for limiting broadcast traffic by dividing the network into segments, ensuring information security, managing and organizing backup paths between broadcast areas;
• The switch is a single-purpose device that effectively segments the network, reduces collision areas and increases the throughput of each end station.
• Blocks uninterruptible power supply– devices to ensure system operability 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 Computing System depends on the requirements and needs of the Customer. Modern technologies allow us to develop an individual option that meets all requirements and objectives.

Laying LAN cables, like other types of cable networks, can be done different ways. When choosing an installation method, they are guided by the individual architectural and design features of the building, its technical characteristics, the presence of existing 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 LAN cables use the construction of walls, floors, and ceilings; this looks more aesthetically pleasing, the routes are protected from extraneous influences, access to them is limited, installation is carried out immediately in special prepared places, and better conditions are provided for subsequent maintenance. Unfortunately, the opportunity to carry out work in a hidden way is rare; more often it is necessary to carry out work in an open way using plastic boxes, vertical columns and trays. Do not forget that there is also a way to lay cables over the air; most often it is used for communication between buildings, when it is not possible to lay the cable in channels or if it is too expensive.

Installing a LAN is a complex and responsible job. , the quality of its implementation determines the stability and correct functioning of the system as a whole, the degree of execution of the tasks assigned to it, the speed of data transfer and processing, the number of errors and other factors. This must be taken very thoroughly and seriously, since any network is the basis (skeleton and circulatory system) of a whole organism of low-current systems responsible for a large number of functions (from Email to the safety of the facility). Each subsequent intervention in the operation of the existing system (expansion, repair, etc.) requires time and money, and their quantity directly depends on the parameters initially built into the system, the quality of the work performed, and the qualifications of developers and performers. Saving money at the stage of design and installation of a LAN can result in much larger expenses at the stage of operation and upgrade