What is included in the LAN. Organization of the locally computing network of the service center with Internet access. Personal Information Collection Options

General concepts

It is not necessary to talk about the role and importance of a competently organized, flawlessly working local computer network of the enterprise. Often it is livised by the guarantor of a successful business. And vice versa with a bad organization, insufficient attention to the issues of its construction and renewal, collapse comes in the organization of labor in the enterprise. If you rephrase a well-known saying, then you can say: "LAN- like air, it is not noticed when it is, and suffocating when it is not."

Everywhere we are faced with various versions of local computing networks. Often out of the houses LAN, growing up to the scale of the area or a whole city, the computing network becomes urban (MAN).

The local computing network must have a number of properties:

Scalability - At the initial stage, the Organization may invest a minimum of funds for laying local networks that would meet its current goals and tasks. In the future, if necessary, it will always be able to easily expand the networks and connect additional equipment.

Flexibility - for timely response to changing requirements of technology to existing local network It is necessary to have its flexibility. In other words, the network must be adapted for most types of network cables: twisted pairs, coaxial, as well as fiber optic, and it is desirable to support technologies, starting OtherNet, FasteThernet, to GigabitetherNet above.

fault tolerance - The system of local networks mandatory includes backup lines in case the main causes of the reasons fail. For example, you can connect the server (server farm) to several switches / routers having spare paths - with one concentrator / router failure, you can always quickly go to another in automatic mode, without interrupting the communication session.

Reliability - Long-term use of a local network in accordance with the increasing need for it implies the need to search for optimal options to increase its reliability, as forced downtime costs to organize too expensive when there is a valuable every minute. Therefore, it is impossible to neglect existing software and hardware and tools that allow to increase the reliability of local networks.

Protection - An important property is the security of networks from an unauthorized invasion, as well as internal user actions. It is solved with the help of a set of measures, including software hardware, a hub, switch, router, firewall, a remote access server, as well as administrative measures, which generally makes it possible to fully control the current processes and ensures the safety of the most important data of the organization.

Controllability - The local network must have powerful tools for its monitoring, to quickly detect interference and faults, to eliminate the possible downtime mentioned above. There are many products designed for the operational collection of technical information about the network status and its parameters - an example can serve as NMP, RMON. In addition, it is possible to control the network via a web interface that can be used almost anywhere for remote access.

In the simplest case, the local computing network consists of two computers equipped with a network card connected to an adjustable cable (coaxial or twisted para). It should be remembered that there is a non-standard patch cord in such a scheme, and the so-called crossover. And of course you need to not forget that the distance is interfrodent to be no more than 100 m.

The solution when the LANSTOTIC of the two-panel can be implemented and on wireless technology, in this case both computers are equipped with wireless network cards (adapters) and are connected in Point-to-point mode.

Network fee Also known as a network card, a network adapter, an Ethernet adapter, NIC (English.NetworkInterface Controller) -Periferial device that allows the computer to interact with other network devices.

SNMP (eng. Simplenetworkmanagement Protocol - Protocol simple control Networks) is a communication network management protocol based on architectureTCP / IP.

RMON-protocol for monitoring computer networks The extension of the SNMP, which is based on the SNMP basis, is the collection and analysis of information on the nature of the information transmitted over the network. Like the CSNMP, the collection of information is carried out by hardware and software agents, the data from which is received by the computer where the network management application has been installed. The distinction of its predecessor consists, first of all, in the nature of the information collected-if the information is characterized by only events that occur on the device where the agent is installed, then that the data obtained has characterized traffic between network devices.

The above-mentioned method of organizing the network of the computer is simple, and does not require special costs, such an implementation of the LAN, meets more and less. However, today's realities are such that there are tens and hundreds of computers and network devices in their composition (switches, gateways, print servers, servers, network devices storage of information, etc.), moreover, practically impressive way out global Network Internet.

The organization of the local network (still donoyakes of the local network) is mandatory begins with the definition of key points. Here is some of them:

· Determining the number of stations (ports, hosts) of the future network;

· Operational data warehouse planning;

· Expected software;

· Estimated services (IP telephony, video observation, etc.);

· Restability of a single information space for the company's structural divisions;

· The probability of using a local network to build a unified corporate information platform (intranet).

There are several options for organizing a local network. As a data transmission environment, a twisted UTP / STP cable can be used (usually category 5E and above) or fiber optic cable. An organization of local networks is possible with wireless technology. In this case, building and configuring the local network will vary greatly depending on the technology used - wireless and wired.

Building a local network will be largely due to its size and method of placing computers. Among other factors affecting the organization and configuration of the local network, it is worth noting the presence of servers, the number of jobs, as well as the number of buildings in which the LAN is functioning.

At the stage of creating a local network and setting up a local network, it is important to have a clear idea of \u200b\u200bthe network architecture (topology). The network topology depends on the location of the PCI of their functional purpose. The choice of topology in the process of creating a local network and setting up the local network is individually - under the specific object of its own architecture.

To carry out the local network, network equipment required for each option is selected, and preferably from one reliable manufacturer.

D-Link offers the entire spectrum of active network equipment for building (upgrading) local computing networks, any level of complexity. In addition, it is important that the fact of the presence of widely extensive service maintenance of the D-Link equipment is important.

After all key points related to the organization of the future network are embarking on the creation of a cable system (in case wired solution LAN).

Intranet (English. INTRANET is also used to intranet ) - Unlike networkinet, it is internal private network Organizations. As a rule, an intranet is an internetune of miniature, which is built on using the exchange protocol and sharing some part of the information within this organization. These can be lists of employees, lists of partner phones and customers. Most often, under this term, only the visible part of the organization is only visible to the internal website. Analyznaya on the Basic HTTP and HTTPS protocols and the client-server principle, an intranet site is available from any computer. Thus, intranet is like a "private" Internet, limited by the virtual space of a separate organization. Intranet allows the use of public communication channels included in the Internet, (VPN), but it provides protection for transmitted data and measures to curb the penetration from outside to corporate nodes.

Structured Cable System (SCS)

Cable system - This is a system, the elements of which are cables and components that are associated with the cable. All applies to cable components passive switching equipment serving for connecting or physical termination of the cable - telecommunication sockets at workplaces, cross and Switching Panels (jargon patch panels ) In telecommunication rooms, couplings and splines.

Recently, when organizing a LAN, in relation to the cable system, the term is most often used. structuralCable system (SCS).

Structured Cable System (SCS) - The basis of the information infrastructure of the enterprise, which allows you to reduce multiple information services for various purposes: local computing and telephone networks, security systems, video surveillance, etc.

SCS it is a hierarchical cable system of a building or group of buildings, divided into structural subsystems. It consists of a set of copper and optical cables, cross-panels, connecting cords, cable connectors, modular sockets, information sockets and auxiliary equipment. All listed items are integrated into unified system and are operated according to certain rules.

Term "Structured" means a robust side, the ability of the system to maintain various telecommunication applications (voice, data and video transmission), on the other hand, the possibility of using various components and products of various manufacturers, and strings - the ability to implement the so-called multimedia environment in which several types of transmitted media are used - Coaxial cable, UTP, STP and optical fiber. The structure of the cable system determines the infrastructure of information technologies (from English, Information Technology), it is she who dictates the content of a specific cable system project in accordance with the requirements of the end user, regardless of active equipment that can be applied subsequently.

Typical installation works SCVNCC:

· Installation of cable channels (boxes, trays, corrugation, pipes, etc.);

· Punching holes in the walls;

· Cable gasket in cable channels;

· Setting out rosettes and seal the cable modules of sockets;

· Assembly and installation of the mounting cabinet;

· Installation and packing of patch panels and organizers.

Stages of mounting SCS:

· Studying an object for mounting SCS;

· Technical project development;

· Selection of the necessary equipment and installation at the facility;

· Testing and certification, delivery of work to the customer;

· After installation support and training

Components SCS

When creating emphasize. Cables ,connectors ,sockets and patch cords used in computing networks. In brief remark:

Copper unshielded UTP cable (eng. Unshieded twisted pair) depending on the electrical and mechanical characteristics, 5 categories are divided into 5 categories (Category 1 - Category5).

Shielded twisted pair of STP (eng. S hieldedtwisted pair) well protects the transmitted signals from external interference, as well as less radiates electromagnetic oscillations internally, which protects, in turn, network users from harmful radiation health. Special place occupied cables categories 6 and 7, which industry began to produce relatively recently. For a Category 6 cable, the characteristics are determined to a frequency of 200 MHz, and for Cable Cables 7 to 600 MHz. Category 7 cables are necessarily shielded, both each pair and the entire cable in the whole. Kabelcategory 6 can be both shielded and unshielded. The main purpose of these cables is support for high-speed protocols on cable segments of a larger length than the UTP Category 5 cable.

8p8c (8 Position 8 Contact) , often erroneously called RJ45 or RJ-45 - The unified connector used in telecommunications has 8 contacts and a latch.

InformantsAs a rule, universal, they serve as a point in the cable system for all office equipment, including not only the computer and other peripheral devices, but also the phone (i.e., it is possible to connect the cord with the RJ-11 (12).

Switching panel (cross-panel, patch panel) - One of the components of the structured cable system (SCS). It is a panel with a plurality of connecting connectors located on the front side of the panel. On the back of the panel there are contacts intended for fixed connections with cables, and connected with electrically connections. Switching panel refers to passive network equipment. Switching panels can be fixed or dialing. If in the first case, all connectors are performed by the same type, then in another case you can implement a hybrid switching panel containing connectors different types, including copper type RJ45 of different categories, fiber-optic connectors of various types, coaxial (for example, type BNC) and others. Types of installed sneakers depend on the type of task solved. The most common type of this type of devices, in modern technologies, is a 24-port fixed switching panel with not shielded connectors of the RJ45 category 5E or 6. From the back of the panel there are so-called IDC connectors (eng. Insulator Displacement Connector, connectivity insulation ).

Picture 78 . Elements SCS

There are two typical ways to use switched panels.

In the first case, the switching panel is used as a switching point between the ports of active network equipment (ASO) and workplaces ports, through the cable of the Horizontal SCS subsystem. Switching is carried out by switching cords from the panel to the ASO ports.

In the second case, the so-called double port representation, the switching panels are used in pairs, one of the panels represents the ASO ports, and the second is the ports of jobs. Switching is carried out by switching cords between panels.

Together with the switching panel it is advisable to use cable organizers To streamline suitable and existing cables.

Switching panels may differ:

but). According to the composition of the connectors

b). By the number of ports

in). By shielding

d). By way of fastening

e). By way of representing ports

Figure 79. Cross-Panel Mounting Example

Switching cord, switching cable or patch cord (from English Patching CORD - connecting cord) - One of the components of the structured cable system. It is an electrical cable to connect one electrical device to another. There may be any types and sizes, on one or both ends of the cable, the connectors connected devices are necessarily present.

The main difference switching cord from cable internal strip - Using a stranded wire, instead of solid. This reduces the transfer characteristics of the cable, but increases flexibility and reduces the minimum radius of the safe cord bending.

Switching cord used in the ambassador pigtail and it is a segment of the cable, terminated on one side by a connector of a certain type. The compound of optical pigtail with a fiber cable is carried out using welding or mechanical deline connections.

Organization SCS

In general, the entire design can be represented in this way: on one of the floors of the building containing workplace With office equipment, along the walls from connected devices and from auxiliary technical means (fire alarm sensors, IDR video surveillance systems.) Horizontal cable wiring is carried out. They converge into a single switting floor assembly (in the same way passing and on the other floors connected to the SCS). From it there is a vertical cable wiring connecting sequentially all the floors. Then the entire cable system is integrated into a common switching center, which can be placed in a special technical room.

All components are plugged with each other and are located in such a way that you can build up the entire system and expand its coverage not only within the multi-storey buildings, structures, but also between real-life objects at a certain distance from each other.

The cable system of the enterprise can be performed in various ways: according to the technology of hidden wiring, in the overhead channels, in space under the raised floor or over the mounted ceiling, etc.

Often, in terms of enterprises, saved on cables, with which the computer is connected to the cable network socket. It should be noted that these patch cords are often the reason for reducing the data transfer rate. They are subjected to the greatest mechanical exposure, while they are made by an unsuitable qualifications. Over time, their parameters deteriorate, which leads to data transfer errors, the appearance of which is quite difficult to notice.

Please note that, according to one of the manufacturers of patch cords, two thirds are not tested. It is difficult to expect the stability of the characteristics of products made in handicrafts, so it is necessary to equip jobs only by professionally performed patch cords.

Each user's working place must be equipped with a power outlet with grounding and information sockets. In small organizations, outlets of existing wiring are usually used. It should be borne in mind that the distance between the power and information sockets of one workplace according to the standard should not exceed 1 m. In addition, if necessary, the intersection of the power cable is necessary, it is necessary to perform at right angles. Often to minimize the effect of the power cable, special cables with shielding are used.

One of the powerful sources of electric interference is luminescent lamps. When laying informational cables, they often do not pay attention to their proximity to such lamps, for example, when installing new tracks over a false ceiling. To reduce the influence of this source, no interference should not be allowed to lay the information cable closer than 15 cm from the fluorescent lamp.

When placing a large number of users in a room that is not equipped with a sufficient amount of power outlets, power and information cables are frequently carried out to the workplace in one channel. According to the standard, if both cables are laid in a common channel, a solid partition should be provided between the power and information compartments.

Modern equipment connected to computer networks often consumes quite a bit of energy. Considering that only two pairs of conductors of twisted pair of four available are used in the data transfer data standards 10/100 Mbps. It is often possible to significantly save on the cable laying if you apply the equipment of the equipment by Ethernet cable. (Power Over Ethernet, PoE).

There are several options to ensure Roe.

The first is to use special switches or already having a function, or supporting it (switches allow the installation of an additional power supply, after which the provision of services is provided). This method is used in the presence of a significant number of ports with a function function, for example, when operating in the organization of IP phones. As an example, the 8-port desktop switch DES-1008PD-LINK with 4 ports.

Figure 80. DES-1008P.

The second method of supplying power through the networkEthernet is in the acquisition of special power supplies included in the "gap" of a network cable (a brown pair of conductors is used to supply the voltage of 48 V. This solution is justified when connecting single devices.

Figure 81. DWL-P200.

DWL-P200 transmits data, and electrical signals to the Ethernet device of one cable.

Special technology is applied in the commutators to check the port. Before serving, special testing is performed on the port, the parameters of the connected equipment are measured and, if it meets the requirements of the Roeing technology, the switch includes power. In the way, in port ports you can safely include conventional devices. When using "mortise" power supplies, especially their cheapest options, you should exclude the possibility of accidentally connecting other equipment.

In accordance with the IEEE 802.3Af Maximum power standard, which can be obtained by the device with a pie port, is 12.95W (with the port must provide power up to 15.4W). Connected devices often consume smaller power, for example, a typical wireless access point consumes About 11W, IP phones - from 2 to 14VTVs depending on the model. In order to save on some models of switches, the total permissible power supply in port router15.4x<количество портов>W In case of exceeding the permissible value of the power consumption, the switch starts to turn off the power of individual ports, given the priorities of the port ports, which the administrator must be assigned manually in accordance with the purpose of the connected equipment.

Fire safety requirements

The basic requirements of fire safety when laying cables in the office are as follows:

cables, Channels, Sockets, etc. must comply with a certain category of fire resistance; This is usually performed using modern ELEMENTS SCS;

power and informational cables when laying in one channel must be separated by a solid partition. The mimic distance from the power cables to information is determined by special standards, depending on the load, but usually should not be less than 12-15 cm;

holes made for laying cables between the rooms should be closed easily removable non-combustible material, for example, cement or low strength plaster, mineral wool, etc.;

when laying cables in space over mounted ceiling, it is unacceptable to use combustible materials.

The advantages of SCS

The first is the universality of SCS, which is that these systems can successfully be used to build computer networks, telephone lines, security, fire systems, as well as for video surveillance and "wiretaps" of a number of rooms.

The second - as already touched above, is easily expanding, which is of great importance in the rapid scientific and technological breakthrough forward. Thanks to this opportunity, there is a problem in the global restructuring of the established Ranesexve for 25 years when connecting new, more advanced devices.

The third is the reliability of the entire design, provided that all components are made in the same manufacturer that the root eliminates possible interference, and failures in the well-established work of connected equipment.

This technology gradually displaces the traditional cable system, and in the near future we will be able to observe a complete transition of enterprises and organizations of various levels on modern SCS.

Need to diagnose SCS

It is clear that any organization is interested in the uninterrupted work of its employees in the enterprise. And it is clear that simple work on the fault of poor-quality installation, as well as untested for compliance with international standards of structured cable systems, turns around much more losses of both temporary and financial nature, rather than their diagnostics. It is very annoying to know that the inability to work with information in the office is connected only with a small cable break or with a defect of some connector.

And in order not to be in an unpleasant situation, you need to diagnose the SCSN physical level. Another reason for the need to study the physical parameters of the network is the impact of these parameters on the test results of higher levels.

Now there are enough instruments in the market for solving such tasks. We will look at two types of devices: cable testers and SCS analyzers.

Cable testers

These devices are the simplest and relatively inexpensive. They are often used to install cables and assess the quality of the built SCS lines. Externally, there are small boxed devices, with the possibilities to identify cliffs, short circuits lived in a pair and between the cores of different pairs, the erroneous polarity of the pair, when the cores are accidentally confusing and with neighboring sites.

In some models of testers, there is a possibility of setting the wiring, as well as establishing the correspondence between the sockets of the switching panel and jobs, in the latter case, all sockets connected to horizontal line Wiring with numbered plugs. When the tester is connected to one side of the cable, its indicator highlights the plug number. Other testers can send a tone on the cable dwelling for its identification and trace.

SCS analyzers

Unlike the aforementioned cable testers, these instruments have a wider range of functions and are designed to determine not only the simplest defects caused by the absence of contact in the cable.

The analyzers are asked to identify more complex malfunctions resulting from incorrect installation when the rules of cable connections in a line (excessive cable stretching, a small bend radius, etc.). From poor-quality installation suffers from productivity worsen their electrical characteristics.

Using these devices in diagnostics, it is possible to determine the integrity of the chain, a characteristic impedance, power and transient attenuation, a signal propagation delay, line length, DC line resistance, line capacity, and electrical symmetry and noise. Such ample diagnostic capabilities determine the high cost of these devices, so they can be purchased away from anyone who deals with the installation and diagnosis of SCS.

Moscow State Mining University

Department Automated systems Office

Course project

under the discipline "Network of computer and telecommunications"

on the topic: "Designing a local computing network"

Performed:

Art. c. AC-1-06

Yurieva Y.G.

Checked:

prof., d. t. n. Shek V.M.

Moscow 2009.

Introduction

1 Design Task

2 Description of the locally computing network

3 Topology Network

4 LAN Scheme

5 OSI reference model

6 Rationale for selecting a local network deployment technology

7 Network Protocols

8 Hardware and Software

9 Calculation of network characteristics

Bibliography

The local computing network (LAN) is a communication system that combines computers and peripheral equipment in a limited territory, usually no more than several buildings or one enterprise. Currently, LAN has become an integral attribute in any computing systems with more than 1 computer.

The main advantages provided by the local network are the possibility of working together and quickly exchanging data, centralized data storage, shared access to shared resources, such as printers, Internet network and others.

Another major function of the local network is the creation of fault-tolerant systems that continue functioning (albeit not in full) at the failure of some elements included in them. In LAN, fault tolerance is ensured by redundancy, duplication; as well as the flexibility of the work of individual parts of the network (computers).

The ultimate goal of creating a local network in an enterprise or to an organization is to improve the efficiency of the computational system as a whole.

The construction of a reliable LAN, which meets the performance requirements and has the lowest cost, is required to begin with the preparation of the plan. In terms of the network is divided into segments, a suitable topology and hardware is selected.

Topology "Tire" is often called a "linear bus" (Linear Bus). This topology refers to the most simple and widespread topologies. It uses one cable, referred to as the main or segment, along which all network computers are connected.

On the network with the Tire topology (Fig.1.) Computers address the data to a specific computer by passing them through the cable in the form of electrical signals.

Fig.1. Topology "Tire"

Data in the form of electrical signals is transmitted to all computers network; However, only the address of which corresponds to the address of the recipient encrypted in these signals is received. And at each time only one computer can transmit.

Since data data is transmitted only by one computer, its performance depends on the number of computers connected to the bus. What are them more, i.e. than more computerswaiting for data transfer, the slower the network.

However, it is impossible to withdraw a direct dependence between network bandwidth and the number of computers. Since in addition to the number of computers, many factors affect the speed of the network, including:

· characteristics hardware computers online;

· The frequency with which computers transmit data;

· Type of working network applications;

· Type of network cable;

· Distance between computers on the network.

Tire - passive topology. This means that computers only "listen" data transmitted over the network, but do not move them from the sender to the recipient. Therefore, if one of the computers fails, it will not affect the work of the rest. In active topologies, computers regenerate signals and transmit them over the network.

Reflection of the signal

Data, or electrical signals extended throughout the network - from one end of the cable to another. If you do not take any special actions, the signal, reaching the end of the cable, will reflect and will not allow other computers to transmit. Therefore, after the data is reached by the addressee, the electrical signals must be repayed.

Terminator

To prevent the reflection of electrical signals, terminators (Terminators) absorb these signals are installed at each end of the cable. All ends of the network cable must be connected to anything, for example, to a computer or barrel connotor - to increase the cable length. To any free - nonconnected - the end of the cable must be connected to the terminator to prevent the electrical signals.

Local network in the office

Example of a local network in the office in a schematic form

Location of equipment in the office, possible cable networks for the office. Communication services: telephony, Internet, television.

Organization of telephone communications in the office with the organization IP telephony for remote employees.

Organization telephone network Companies using the Internet. Creating a telephone network with high quality telephone connection. Organization of free telephone calls for customers.

Local network scheme

Features of the local network

An example of a local network is given for a more understandable and informative presentation of the network with the prioritization of the transfer. different species Traffic: Internet, telephone traffic, television.

Local network scheme

In modern conditions, tough competition is important to respond quickly to any changes. Stability of any company, cafe, shop or large corporation Directly depends on the reliability and well-thought-out typology of the local network.

Key benefits of local business networks:

Continuous access of employees to documents, databases directly from the workplace;

Instant sharing reports between departments;

Organization of joint access to office equipment (printers, chamfer, copiers, scanners);

Organization of access to the Internet from all workstations;

The ability to automate routine processes;

Organization of free and protected corporate relations between individual cabinets, buildings.

A competently designed locally computing network at times increases the efficiency of the enterprise, allows you to free up human resources, provides a lot of additional opportunities

Why is the development of a corporate local network to entrust CANMOS?

In small offices, where you need to connect two to three computers, the local network can be organized by your own. But most enterprises are better to trust a specialized company.

Without experience, practical skills and knowledge of the network equipment market, a serious budget is possible without achieving the desired result. Sometimes, the incorrect connection or savings on cable and connectors leads to the fact that the expensive equipment works only by 10-20% of its capabilities. As a result, constant delays, failures, burning ports or the system failure at all.

Without the development of a detailed plan, after completion, it may turn out that they forgot to lay a line for a network printer, and in the router all ports are busy and no ability to connect another device. Since the scaling was not provided in advance, with the expansion of the office "stick new" computers naturally nowhere.

With CANMOS, all network problems will go to the past. For many years we have been providing communication services and design data transmission systems. When developing a network, we:

We think in detail the topology to satisfy all the needs of your enterprise for functionality;

Consider the scaling and convenient addition of new workstations with minimal investment;

Provide protection from external and internal threats;

We guarantee the ease of control.

Typical Local Network Scheme from Canmos

When designing a LAN, preference is given to the Star typology - each node (computers, network printers) Connect to the switch by a separate cable. Such a solution provides:

Independent work of each workstation, which increases the reliability of the network;

The minimum cost and simplicity of adding new devices to the network when expanding the enterprise.

To improve reliability and fault tolerance, simplifying administration, optimizing the loads between the network equipment, the locally computing network is divided into several segments - subnets are connected to each other with high-speed optical channel. In a separate segment, mail servers, file and 1c, PBX are operating.

To simplify administration, computers from different departments, such as accounting, commercial or legal unites in the working groups.

Wireless Network Access provides Wi-Fi access points.

Technically, when laying LAN-networks, the optimal server and network equipment is placed in a separate room, to provide quick access From one place for the administrator of the network. A sockets for RJ-45 and RJ-12 (for IP-16Efony) are displayed near the employees' workplaces.

In the future, depending on the needs of the enterprise, office IP telephony can be deployed on the basis of a finished local network (for a stable connection, prioritization with a speed isolated 64 kb per unit), 1C network. A secure (encrypted) connection to the local network of remote employees can be connected to the VPN channel.

Local computing networks. Types and characteristics of LAN

Local computing network it is a system of distributed data processing, covering a small area (diameter to 10 km) inside agencies, research institutes, universities, banks, offices, etc., this is a system of interconnected and distributed in fixed areas of means of transmission and processing information oriented information oriented National resources - hardware, information, software. LAN can be viewed as a communication system that supports within one building or some limited territory one or more high-speed information transmission channels provided by connected subscriber systems (AC) for short-term use.

In the generalized structure of the LAN A set of subscriber nodes, or systems (their number can be from tens to hundreds), servers and communication subnets (KP).

The main components of the network are cables (transmitting environments), workstations (networkwheel networks), network interface board (network adapters), network servers.

Workstations (PC) In LAN, serve as a rule, personal computers (PCs). On PC users of the network implemented applied tasks, the execution of which is associated with the concept of the computing process.

Network servers - These are hardware and software systems that perform common access network distribution functions that can work and as a regular subscriber system. As a hardware server, a fairly powerful PC, mini-computer, a large computer or a computer designed specifically as a server are used. There may be several different servers to manage network resources, however, there is always one (or more) file server (database server) to control external memory general access and organization of distributed databases (RBD).

Workstations and servers are connected to the cable of the communication subnet using interface cards - network adapters (CA). The main functions of the Ca: the organization of receiving data from (c) PC, negotiation speed of receiving information (buffering), generating a data packet, parallel-serial conversion (conversion), encoding (decoding) data, checking the correctness of the transmission, setting Connections with the required subscriber of the network, the organization of the exchange itself. In some cases, the list of SA functions is significantly increasing, and then they are built on the basis of microprocessors and built-in modems.

In the LAN, twisted pair, coaxial cable and fiber optic cable are used as cable transmitters.

In addition to the specified one, the following is used in the LAN network hardware:

transceivers (transceivers) and repeators (repeaters) - to combine the segments of the local network with a tire topology;

hubs (hubs) - to form a network of arbitrary topology (active and passive hubs are used);

bridges - for combining local networks into a single integer and increase the performance of this whole by adjusting traffic (user data) between individual subnets;

routers and switches - To implement switching and routing functions when managing a schedule in segmented (consisting of interconnected segments) networks. Unlike bridges providing network segmentation at the physical level, routers perform a number of "intelligent" functions when controlling the schedule. Switches, performing almost the same functions as routers, exceed them in terms of performance and have less latency (hardware temporal delay between receiving and sending information);

modems (modulators - demodulators) - to match the digital signals generated by a computer, with analog signals of a typical modern telephone line;

analyzers - to control the quality of network functioning;

network testers - To check cables and find faults in the system of installed cables.

The main characteristics of the LAN:

The territorial length of the network (the length of the total communication channel);

Maximum data transfer rate;

Maximum number AC online;

The maximum possible distance between the workstations on the network;

Network topology;

View of the physical data environment;

Maximum number of data channels;

Signal transmission type (synchronous or asynchronous);

The subscriber access method into the network;

Network software structure;

The possibility of transmitting speech and video signals;

Conditions of reliable networking;

Ability to communicate LANs with each other and with a network more high level;

The ability to use prioritization procedures while connecting subscribers to a shared channel.

To the most typical application areas of LAN relate the following.

Treatment of texts - One of the most common functions of information processing tools used in LANs. Transfer and processing of information on the network deployed at the enterprise (in the organization, university, etc.), provides a real transition to the "paperless" technology, ousting fully or partially writing machines.

Organization of own information systems, Compound automated databases are individual and general, concentrated and distributed. Such databases may be in every organization or company.

Information exchange between the network of the network is an important means of cutting to a minimum of paper document management. Data transfer and communication occupy a special place among network applications, as this is the main condition for the normal functioning of modern organizations.

Ensuring distributed data processing , associated with the union of AWP of all specialists in this organization to the network. Despite the significant differences in the nature and volume of settlements carried out on the AWS specialists of various profiles used in this information, as part of the same organization, is usually located in a single (integrated) database. Therefore, the combination of such arm in the network is appropriate and a very effective solution.

Support for making management decisions, Providing managers and managerial personnel organizations reliable and operational information needed to assess the situation and adopt the right decisions.

Organization email - One of the types of LAN services that allow managers and all employees of the enterprise to promptly receive all sorts of information necessary in its production and economic, commercial and trading activities.

Collective use of expensive resources - The necessary condition for reducing the cost of work performed in the procedure for implementing the above applications of LANs. We are talking about resources such as high-speed printing devices, storage devices of high capacity, powerful information processing tools, application software systems, databases, knowledge bases. Obviously, such funds are inexpedient (due to the low utilization rate and high cost) have in each subscriber network system. Enough if these tools are available on the network in one or more copies, but access to them is provided for all ac.

Depending on the nature of the organization's activities, in which one or more local networks are deployed, the specified functions are implemented in a certain combination. In addition, other functions specific to this organization can be performed.

Types of LAN. To divide the LAN on groups, certain classification features are used.

By destination LANs are divided into informational (information and search), controlling (technological, administrative, organizational and other processes), calculated, information and calculated, documentary information processing, etc.

By type used on the network computer They can be divided into inhomogeneous, where various classes (micro, mini-large) and models (inside classes) are used, as well as various subscriber equipment, and homogeneous, containing the same computer models and the same type of subscriptions.

On management organization Uniform LAN differ on the networks with centralized and decentralized control.

In centralized control networks, one or more machines (central systems or organs), network managers stand out. Disclaimed machines called file servers or database servers are available to all other computers (workstations) of the network. On servers there is a network OS, usually multitasky. Workstations have access to server disks and shared printers, but, as a rule, cannot work directly with other PC disks. Servers can be allocated, and then they only perform network management tasks and are not used as PC, or unproduced when parallel with the network management task performs user programs (this reduces server performance and the reliability of the entire network due to a possible error in the user program which can lead to a network stop). Such networks are characterized by simplication of the interaction functions between the AC LAN, but their use is advisable at a relatively small number of the AU on the network. In centralized control networks, most of the information and computational resources are concentrated in the central system. They also differ also a more reliable information security system.

If the information and computational resources of the LAN are uniformly distributed by a large number of AC, centralized management is ineffective due to a sharp increase in the service (managing) information. In this case, networks are effective with decentralized (distributed) control, or peer-to-peer. In such networks there are no dedicated servers, the network management functions are transmitted in turn from one PC to another. Workstations have access to disks and printers of other PCs. This facilitates the joint work of user groups, but the network performance is somewhat low. Disadvantages of peer-to-peer networks: the dependence of the efficiency of the network functioning on the number of speakers, the complexity of the network management, the complexity of ensuring information protection from unauthorized access.

Data transfer rate In the general channel distinguish:

LAN with a small bandwidth (units of megabits per second), in which a vibrant steam or coaxial cable is used as a physical transmitting medium;

LAN with medium bandwidth (dozens of megabits per second), in which a coaxial cable or twisted pair is also used;

LAN with high bandwidth (hundreds of megabits per second), where fiber optic cables are used (light guides). By topology, those. Configurations of elements in the LAN network are divided: on, total tire, ring, star, etc. By topology . Configurations of elements in TVS, networks can be divided into two classes: broadcast (Fig. 1) and successive (Fig. 2). Broadcast configurations and a significant part of consecutive configurations (ring, a star with an "intelligent center", hierarchical) are characteristic of LAN. For global and regional networks, an arbitrary (cellular) topology is the most common. Found the use of hierarchical configuration and star.

Fig. 1. Broadcast Network Configurations: A - Total Bus;

b - tree; B - Star with the Passive Center

Fig. 2. Sequential configurations of networks A - arbitrary (cellular), b - hierarchical; in - ring, g - chain; D - Star with "Intellectual" Center

Virtual LAN

Virtual local computing network (VLVS) is called a logically combined group of LAN users as opposed to a physical association based on the territorial sign and network topology. Such networks completely eliminate physical barriers on the basis of the formation of the Investments' Working Groups on a higher-level network, but it is especially true on the scale of the corporate computing network (KVC), since the possibility of combining physically dispersed employees of the company to the Group's integrity preservation within their groups. This ensures a high organizational flexibility in managing the company. The VLVS technology allows network administrators to group different users of the FCS, jointly using the same network resources. The splitting of the CCC to the logical segments, each of which is VLVS, provides significant advantages in network administration, ensuring information security, in the management of broadcast transmissions from the virtual network on the corporate network highway.

To organize and ensure the functioning of the VLVS, such main components are used:

High-performance switches designed for logical segmentation of end stations connected to them;

Routers operating on the network level model VOS and ensuring the expansion of virtual interaction with workgroups and increase compatibility with LANs installed;

Transport protocols governing the transmission of TRVS traffic through the highway shared LAN and ATM networks;

Solutions for managing networks that offer centralized management functions, configuring and managing schedule.

These components allow you to merge users into virtual networks based on ports, addresses or protocols.

VLVS, based on ports, is the easiest way to group network devices. With such an organization of a virtual network, all remote devices attributed to certain high-performance network switch ports are combined into one VLVS regardless of their addresses, protocols, applications.

A virtual network based on addresses can support multiple user groups on the same switched port. The corresponding devices of these working groups are combined in a subnet based on their addresses.

In a virtual network based on protocols, are combined into various logic groups of network devices based on IP protocols, IPX, etc. These devices usually work on the network level and are called routers. If they are able to combine work with several protocols, then multiprotocol routers.

In the title, the local computing network has already laid the assignment, function and system limitations. We will analyze the name to the components. Local, formed from the English Local - local, that is, the network is tied to a specific geographical location and has restrictions on the territory, computing, associated with network composition (computing equipment, software) and its appointment, net - implies a combination of computing equipment and software on a certain territory (local) to the network (by means of cables).

In this way, it is possible to formulate a definition of a locally computing network (LAN) - this is a system of interconnected computing resources (computers, servers, routers, software, etc.) distributed by relatively small territory (office or group of buildings), serving for receiving and transfer, storage and processing information of various kinds.

Different locally computing networks can function individually or be interconnected using communications tools, such as enterprises with a branch network in different cities. Thanks to this connection, the user can interact with other workstations connected to this locally computing network. There are local networks whose nodes are separated by geographically at a distance of more than 12,500 km (space stations and orbital centers), but they still belong to local.

The assignment of the LAN is to ensure the joint and simultaneous access of a certain group of persons to data, programs and equipment (computers, printers, charts, file storage and processing devices, and databases) and data transmission (electronic graphics, text processing, email, access to remote bases data, digital speech transmission).

For example: the manager accepts an order and introduces it to the computer, then the order enters the accounting department and there is an invoice, at the same time information may come in legal service To create a contract.

Characteristics of LAN:

• High-speed channels (1- 400 Mb С) belonging to predominantly one user;
• The distance between workstations connected to the local network is usually from several hundred and several thousand meters;
• Transmission of data between computer member stations;
• Decentralization of terminal equipment, which uses microprocessors, displays, cash registers, etc.
• Data transfer to subscribers connected to the network, on a shared cable;

The main functions of the LAN are:

• Ensuring simultaneous access to equipment, software and information, combined into a network;
• Minimizing the risk of unauthorized access to information and network resources;
• Delimitation of access to information and network resources;
• Ensuring fast and confidential exchange and simultaneous work with information to a certain circle of persons;
• Control of information flows, including incoming and outgoing;
• The distinction of control functions and responsible persons on each node (for each node corresponds to the system administrator performing the servicing and, as a rule, control functions);
• Optimization of software and equipment costs due to their collective use (for example one printer into several departments, etc.)

As a result of the use of LAN unite personal computerslocated on many remote workplaces. Employee jobs cease to be isolated and combined into a single system that has its own special advantages:

• The ability to remote access to equipment, software and information;
• Optimization of processor operation resources;
• Fewer errors intensity compared to the telephone database network;
• Bandwidth higher than the global network;
• The possibility of reconfiguration and development by connecting new terminals

Application area Local 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, say 1C: Accounting, etc.). Every day, information flows are becoming more, the software used is comprehensive and functional, the geography of the activities of organizations is expanding. The use of LAN funds becomes not just desirable, but necessary for the successful activity and development of business, science, training of students, schoolchildren, training and retraining of specialists, the fulfillment of government programs and functions, etc.

Network functioning structure.

The structure of the local network is determined by the principle of management and communication type, it is often based on the structure of the serviced organization. Topology types are used: tire, annular, radial, tree. The most common two two types, due to effective use Communication channels, ease of management, flexible expansion and change capabilities.

Topology "Tire" - All computers are binding to a chain, connecting to a trunk cable segment (barrel), "Terminators" are placed at its ends, to clean the signal spreading in both directions. Computers in the network are connected coaxial cable with a tee connector. Network bandwidth is 10 Mbps, for modern applications that actively use video and multimedia data, this is not enough. The advantage of this topology lies in the low cost of posting and unification of connections.

Tire topology is passive. A failure of one computer does not affect network performance. Damage to the main cable (tires) leads to a reflection of the signal and the entire network as a whole becomes inoperable. Turning off and especially connection to such a network requires a tire break, which causes a violation of the circulating flow of information and the system freezing.

Topology "Tree" - A more advanced configuration of the type "tire". Several simple tires are attached to the common trunk bus through active repeaters or passive multipliers.

Topology "Star" (Star) - is the most high-speed of all topologies, information between peripheral workstations passes through the central node of the computing network. Central Control Node - file server It can implement the optimal protection mechanism against unauthorized access to information. The entire computing network can be controlled from its center.

The cable connection is pretty simple, as each workstation is connected only with the central node. The cost of laying cables is high enough, especially when the central node is geographically located not in the center of the topology. When expanding computing networks, previously performed cable connections cannot be used: a separate cable from the center of the network must be used to a new workplace.

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

Topology "Ring" (Ring) - Computers are connected by a cable segments having a ring shape, fundamentally identical to the tire, except for the need to use "Terminators". In the event of a malfunction of one of the network segments, the entire network fails.

Signals are transmitted only in one direction. Each station is directly connected to two adjacent, but listens to the transmission of any station. The ring is several transceivers and the physical environment connecting them. All stations may have equal access rights to the physical environment. At the same time, one of the stations can perform the role of an active monitor serving the exchange of information. The cable laying from one workstation to another can be quite complex and expensive, especially if geographically workstations are located far from the ring (for example, in line).

The main problem with the ring topology is that each workstation should actively participate in sending information, and in case of failure, at least one of them, the entire network is paralyzed. Faults in cable connections are easily localized. Connecting a new workstation requires a network shutdown, as the ring must be open during installation. Restrictions on the length of the computing network does not exist, as it ultimately is determined exclusively by the distance between the two workstations.

Computers can be connected with each other using different access media: copper conductors (twisted pair), optical conductors (optical cables) and through radio channels ( wireless technology). Wired, optical connections are installed via Ethernet, wireless - via Wi-Fi, Bluetooth, GPRS and other means. Most often local networks are built on ethernet technologies or Wi-Fi. It should be noted that the Frame Relay protocols were previously used, Token Ring.that today meet more and less often, they can be seen only in specialized laboratories, educational institutions and services.

Construction components of a simple local network are used:

• Adapter (Network Adapter) - a device connecting the computer (terminal) with a network segment;
• Bridge (Bridge) is a device connecting local or remote network segments;
• Router (Router) - a device for limiting broadcast traffic by splitting the network to segments, ensuring information protection, management and organization of backup paths between broadcasting areas;
• Switch - a narrowing device, effectively segmented network, reduces collision areas and increases throughput Each terminal station.
• Blocks uninterrupted power - Devices to ensure the operation of the system in cases of disconnecting the main power source.

Installation of the locally computing network (LAN)

The choice of the type of topology, the access environment and the locally computing 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.

The laying of LAN cables, as well as other types of cable networks can be carried out. different ways. When choosing a method of installation, it is guided by individual architectural and constructive features Buildings, It technical characteristics, the presence of existing networks and other equipment, the procedure for the interaction of low-current systems with other systems. You can fundamentally allocate two methods - open and hidden. For hidden wiring of LAN cables, the design of walls, floors, the ceilings are more aesthetic, the tracks are protected from extraneous influences, access to them is limited, the gasket is made immediately into special prepared places, the best conditions are provided for subsequent maintenance. Unfortunately, the ability to perform work with a hidden way is rare, more often it is necessary to carry out operating in the open method using plastic boxes, vertical columns and trays. Do not forget that there is still a way of laying cables by air, most often it is used to communicate buildings, when there is no possibility to pave the cable into the channels or if it is too expensive.

Installation of LAN is a complex and responsible work. The quality of its implementation depends the stability and correctness of the functioning of the system as a whole, the degree of execution of tasks assigned to it, the rate of transmission and data processing, the number of errors, etc. Factors. It is necessary to relate to this very thoroughly and seriously, since any network is the basis (skeleton and blood system) of a whole body from low-current systems responsible for a large number of functions (from email to object safety). Each subsequent intervention in the operation of the current system (expansion, repair, etc.), requires the cost of time and means, and their number on direct depends on the parameters initially laid down in the system, the quality of work performed, the qualifications of developers and performers. Saving funds at the design and installation of the LAN, can turn out much larger spending at the stage of operation and abgrade