A local area network is a concept familiar to many firsthand. Almost every enterprise uses this technology, so it can be argued that every person has come across it in one way or another. Local networks significantly accelerated production processes, thereby giving a sharp jump to their further use around the globe. All this makes it possible to predict the further growth and development of such a data transmission system, up to the introduction of a LAN in every, even the smallest enterprise.
A local area network is a number of computers interconnected by special equipment that allows for a full-fledged exchange of information between them. An important feature of this type of data transmission is the relatively small territory for the location of communication nodes, that is, the computers themselves.
Local networks not only greatly facilitate the interaction between users, but also perform some other functions:
A local area network can be represented by two models: a peer-to-peer network and a hierarchical one. They differ in the way communication nodes interact.
A peer-to-peer network is based on the equality of all machines, and data is distributed between each of them. Essentially, a user of one computer can access the resources and information of another. The efficiency of the peer-to-peer model directly depends on the number of working nodes, and its security level is unsatisfactory, which, coupled with a rather complicated management process, makes such networks not very reliable and convenient.
The hierarchical model includes one (or more) main server, where all data is stored and processed, and several client nodes. This type of network is used much more often than the first, having the advantage of speed, reliability and security. However, the speed of such a LAN largely depends on the server, which under certain conditions can be considered a disadvantage.
Designing a local area network is a rather complicated process. It begins with the development of a technical task, which should be carefully considered, since shortcomings in it threaten subsequent difficulties in building a network and additional financial costs. Primary design can be done using special configurators that will allow you to choose the optimal network hardware. Such programs are especially convenient in that you can correct various values and parameters directly during operation, as well as draw up a report at the end of the process. Only after these steps will it be possible to proceed to the next stage.
This stage consists in collecting data about the enterprise where it is planned to install a local area network, and analyzing the information received. Quantity is determined:
An important point is the availability of data on the paths of laying highways and planning a specific topology. In general, it is necessary to adhere to a number of requirements that the IEEE 802.3 standard imposes. However, despite these rules, it may sometimes be necessary to calculate propagation delays or consult network equipment manufacturers.
When choosing a method for placing communication nodes, it is necessary to remember the basic requirements for local networks:
The network topology is the physical layout of the network, significantly affecting the main characteristics. Three types of topologies are mainly used in modern enterprises: "Star", "Bus" and "Ring".
The star topology is the most common and has many advantages over the others. This method of installation is highly reliable; if any computer fails (except for the server), it will not affect the operation of the others.
Topology "Bus" is a single backbone cable with connected computers. Such an organization of a local area network saves money, but is not suitable for combining a large number of computers.
The "Ring" topology is characterized by low reliability due to the special arrangement of nodes - each of them is connected to two others using network cards. The failure of one computer leads to a shutdown of the entire network, so this type of topology is used less and less.
The local area network of an enterprise also includes various technologies, equipment and cables. Therefore, the next step will be the selection of all these elements. The decision in favor of this or that software or hardware is determined by the purpose of creating a network, the number of users, the list of programs used, the size of the network, and its location. Currently, fiber optic backbones are most often used, which are distinguished by high reliability, speed and availability.
Cables are used in networks to transmit signals between workstations, each of them has its own characteristics, which must be taken into account when designing a LAN.
The network equipment of local area networks includes many elements, the most commonly used among which are:
The hardware of the local area network necessarily includes the server and client parts.
The server is powerful computer, which has a high network significance. Its functions are to store information, databases, serve users and process program codes. Servers are located in special rooms with controlled constant air temperature - server rooms, and their body is equipped with additional protection from dust, accidental shutdown, as well as a powerful cooling system. As a rule, only system administrators or business leaders.
A workstation is a normal computer connected to the network, that is, it is any computer that requests services from the main server. To provide communication on such nodes, a modem and a network card are used. Since workstations usually use server resources, the client part is equipped with weak memory bars and small hard drives.
The equipment of local area networks will not be able to fully carry out its functions without suitable software. The software part includes:
Designing a local area network requires a long and unhurried analysis, as well as taking into account all the subtleties. It is important to provide for the possibility of enterprise growth, which will entail an increase in the scale of the local network. It is necessary to draw up a project in such a way that the LAN is ready at any time to connect a new workstation or other device, as well as the modernization of any of its components and components.
Equally important are security issues. The cables used in the construction of the network must be reliably protected from unauthorized access, and the trunks should be placed away from potentially dangerous places where they can be damaged - either accidentally or intentionally. LAN components located outside the premises must be grounded and securely fastened without fail.
The development of a local area network is a rather labor-intensive process, however, with right approach and due accountability, the LAN will operate reliably and stably, providing uninterrupted user experience.
constitute active devices that provide information transfer between network nodes. The list of such devices includes network adapters, network hubs and switches, bridges and routers.The purpose of network hubs and switches is similar - the connection of several LAN nodes lying within the same segment. The difference is that the hub broadcasts traffic from one node to all available, and the switch - directly to the recipient node. This or that Hardware LAN can be selected depending, first of all, on the information load of the network and the requirements for the security of data transmission. In networks whose nodes are not critical to traffic volumes, hubs are quite enough. Networks that place high demands on data performance and security should be equipped with switches that eliminate the need and ability for network nodes to process information that is not intended for them.
Bridges and routers are LAN hardware, which provides communication between network segments. Routers, unlike bridges operating at the data link layer - the second in the OSI model, use the third layer of the model - network. This allows you to transfer packets taking into account the specifics of protocols, to select the optimal route for transmitting a packet based on the analysis of information received from other routers about the topology and state of the network. The bridge is transparent to all network protocols and, like switches, decides to forward a packet based only on the destination MAC address.
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Structural is a graphical document that displays the physical location and connection of the components of the SCS.
Only qualified specialists officially authorized to work in electrical installations should be trusted.
To combine computers is currently used a large number of various devices(network hardware). In local area networks, network adapters are most commonly used ( network cards), hubs, switches, routers.
Let's take a closer look at each type of equipment.
Network adapter- This is a device necessary to connect a computer to a local network. The network adapter is installed in a free slot (connector) motherboard computer, as well as adapters that perform other functions, such as a video adapter. Network adapters can be classified according to the following criteria:
Depending on the type and capacity of the internal bus used in the computer;
Depending on the type accepted in the network network technology– Ethernet, Token Ring, FDDI, etc.;
Depending on the type of medium (channel) of data transmission - coaxial cable, fiber optic cable, twisted pair cable.
The network adapter is attached to the cable using special connectors, the type of which depends on the type of cable. For example, for a twisted pair cable, an RG-45 type connector is used, which looks like a phone jack. To connect to a coaxial cable, so-called BNC connectors and T-connectors are used. There are network adapters that use the wireless principle of interaction. At present, the three main types wireless transmission data are radio, microwave, and infrared. The most common, at present, option for organizing a wireless local area network is the use of WiFi equipment. WiFi is an abbreviation for "Wireless Fidelity" (wireless communication) and is a wireless access standard that provides information transfer rates up to 54 Mbps.
Every network adapter has a unique internal number, the so-called MAC address, which allows you to uniquely identify the source of information in the network environment.
Various types cables used as carriers, or transmission media. Although wireless technology As data transmissions become more and more popular nowadays, cable remains the main type of carrier for network communications. The most common cable types are:
twisted-pair cable;
· coaxial cable;
· fiber optic cable.
concentrator(multiport repeater, or HUB) is a device used to combine individual workstations (computers) into a local network. Modern hubs usually have 8, 12, 16, 24, or 48 ports (connectors) for connecting computers. All hub ports are equal. When a signal is received from one of the computers connected to it, the hub broadcasts it to all other ports. Thus, a hub is the central connection point for computers on a network.
Switch(switch) is a device that can also be used to combine computers, or different segments of a local network. Unlike a hub, when a switch receives a signal (data packet) from one of the computers connected to it, it does not broadcast it to all other ports, but only transmits it to the port to which the computer that is the recipient of this data packet is connected.
router(router) is a network communication device that performs information routing, i.e. determining the best route for information transfer from source to destination and transferring information along this route. Routers connect several subnets into an internetwork, and therefore the transfer of information from one computer to another is possible along several routes.
Local networks
Software computer networks consists of three components:
As a standalone operating system for workstations, as a rule, modern 32-bit operating systems are used - Windows 95/98, Windows 2000, Windows XP, Windows VISTA, Windows 7 (Seven), Windows 8, Windows 8.1, Windows 10.
The following are used as network operating systems in computer networks:
Network operating systems are needed to manage the flow of messages between workstations and servers. They organize collective access to all network resources.
Getting access to the resources of local area networks involves the implementation of three procedures: identification, authentication and authorization:
Most network operating systems have built-in protocol support (TCP/IP, IPX/SPX, NetBEUI):
For users of local area networks, a set of network services is of great interest, with the help of which he gets the opportunity to view a list of computers available on the network, read remote file, print a document on a printer installed on another computer on the network, or send an email message.
The implementation of network services is carried out by software ( software tools). File Service and the print service are provided by the operating systems, while the rest of the services are provided by the network application programs or applications. Traditional network services include: Telnet, FTP, HTTP, SMTP, POP-3.
The Telnet service allows you to organize user connections to the server using the Telnet protocol.
The FTP service allows you to transfer files from Web servers. This service is provided by web browsers ( Internet Explorer, Mozilla Firefox, Opera, etc.)
HTTP - a service designed to view Web pages (Web sites) is provided by network applications: Internet Explorer, Mozilla Firefox, Opera, etc.
SMTP, POP-3 - inbound and outbound services Email. Implemented by mail applications: Outlook Express, The Bat and etc.
PURPOSE AND CLASSIFICATION OF COMPUTER NETWORKS
Services of the global Internet.
Global network Internet. Addressing.
Purpose and classification of computer networks.
INTERNET TECHNOLOGIES
Plan:
Computer network– communication system of computers and computer equipment.
Depending on the territorial location of subscriber systems, computer networks can be divided into three main classes:
Global Area Network (WAN - Wide Area Network) is a system of networked computers located on long distances from each other.
Regional computer network (MAN - Metropolitan Area Network) connects subscribers located at a considerable distance from each other (tens - hundreds of kilometers).
Local area network (LAN, LAN - Local Area Network) unites subscribers located within a small area (2 - 2.5 km.).
Local area network hardware includes workstations, server, communication equipment
Work station- a personal computer connected to the network and providing user access to its resources.
Server- a specialized computer on the network, designed to run service software on it.
To connect a workstation with a communication channel, use network adapter.
Communication channel in a computer network is the physical medium of information transmission.
Communication channels differ in three main properties: bandwidth, noise immunity, cost.
Bandwidth is the maximum data transfer rate over the channel. It is usually expressed in kilobits per second (Kbps) or megabits per second (Mbps).
Consider communication channels.
twisted pair characterized by poor noise immunity and low data transfer rate of 0.25 - 1 Mbps. Low cost.
Coaxial cable has high noise immunity and provides information transfer rate up to 10-50 Mbps.
Fiber optic cable is not affected by electromagnetic fields and has practically no radiation itself. Information transfer rate over 50 Mbps.
Wireless network. Wireless technologies in computer networks are based on coding and transmission of signals in the form of electromagnetic radiation.
The most common standards for data transmission in the radio wave range: Bluetooth, Wi-Fi, GPRS, Wi-Max, 3G, LTE.
There are standards for data transmission in the light range: infrared - IrDa, etc.
Communication equipment:
network hub or hub– network device, designed to combine multiple Ethernet devices on a common network segment. Devices are connected using twisted pair, coaxial cable or fiber.
Currently, hubs are almost not produced - they were replaced by network switch (switches)- devices designed to connect several network nodes within one or more network segments.
Router (router)– a device that provides connection of administratively independent communication networks.
Bridge is a device that connects two networks using the same data transmission methods
Gateway- This is a device that allows you to organize the exchange of data between two networks using different communication protocols.
