Combining computers in a local network

The local network — combining several computers located at a short distance from each other (usually within the same building) for the joint solution of information, computing, educational and other tasks. In a small local network there can be 10-20 computers, in a very large one - about 1000.
Purpose local networks
Sharing common hardware (printer drives, modems)
· real-time data exchange
information system of an enterprise (institution)
Organization local networks.
Although there are many different ways to connect computers, there are essentially two types of computer networks: peer-to-peer network and client-server network.
peer-to-peer network is an association of equal computers. Typically, a peer-to-peer network unites no more than 10 computers and is organized in homes or small offices.

Client server network more common in organizations such as a school, business, or library rather than in the home. In this type of network, one computer, called the server, is the heart of the network. It stores information and resources and makes them available to other computers on the same network. Other computers that use the network to obtain this information are called clients.

Client-server networks are the best option for networking more than ten computers. They are more expensive, but in cases where you need to store a large amount of information, this is the best choice.
Models of various network configurations
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Topologies local networks
Local networks depending on the purpose and technical may have different configurations. The general scheme of connecting computers in a local network is called the network topology. Network topologies can be different. Most often, local networks can have a "bus" and "star" topology. In the first case, all computers are connected to one common cable (bus), in the second case, there is a special central device (hub), from which "beams" go to each computer, i.e. each computer is connected to its own cable.
IN tire topology, computers are connected to a common channel (bus) through which they can exchange messages.

The bus-type structure is simpler and more economical, since it does not require an additional device and consumes less cable. But it is very sensitive to cable system failures. If the cable is damaged in at least one place, then there are problems for the entire network. The fault location is difficult to locate.
IN radial topology ("star" topology) in the center there is a concentrator that sequentially communicates with subscribers and connects them with each other.

In this sense, the "star" is more stable. A damaged cable is a problem for one particular computer; it does not affect the operation of the network as a whole. No troubleshooting required
IN annular topology information is transmitted over a closed channel. Each subscriber is directly connected to the two closest ones, although in principle it is able to contact any subscriber in the network.

In a network having a "ring" type structure, information is transmitted between stations along the ring with hopping in each network controller. Reception is carried out through buffer drives made on the basis of random access memory devices, therefore, if they fail in one network controller, the operation of the entire ring may be disrupted. The advantage of the ring structure is the ease of implementation of devices, and the disadvantage is low reliability.
hybrid a topology is a combination of different topologies in a single network. For example, you can connect multiple star networks with a single cable.
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Equipment local network
How do computers communicate with each other?
The operation of the network is based on the fact that all elements of the equipment are connected to each other in one way or another. Each computer and equipment, such as printers, scanners, laptops, is connected using a cable of various sizes, satellite communications or telephone lines. Today, there are even wireless networks that connect computers using radio waves.
LAN equipment generally includes:
computers (servers and workstations);
network boards (adapters);
· channels of connection;
special devices that support the functioning of the network (routers, hubs, switches).
Each computer connects to the network using a network card − adapter.
The network card is connected to the network cable. If radio or infrared communication is used, no cable is required. In modern local networks, two types of network cables are most often used:
Unshielded twisted pair
fiber optic cable.
Typically, the choice of a cable for a network depends on the following indicators: the cost of installation and maintenance, data transfer rate, limitation on the distance of information transfer without additional repeater amplifiers (repeaters), data transfer security.
is a set of eight wires twisted in pairs in such a way as to provide protection against electromagnetic interference.

Twisted pair is the cheapest type of cable. Twisted pair allows a maximum transmission rate of up to 10 Mbps. The cable length should not exceed 1000 meters, and the data transfer rate will not exceed 1 Mbps. Shielded twisted pair is used to improve noise immunity. Each twisted pair connects only one computer to the network, so the connection failure affects only this computer, which allows you to quickly find and fix faults.
fiber optic cables transmit data in the form of light pulses along glass wires. Fiber optic cables provide the highest transmission speed; they are more reliable, as they are not subject to electromagnetic interference.
Optical cable is very thin and flexible, making it easier to transport than heavier copper cable. The data transfer rate over an optical cable is hundreds of thousands of megabits per second, which is about a thousand times faster than over twisted pair wires.

An optical fiber line is the most expensive type of connection today, but the speed of information propagation in it reaches several gigabits per second with an allowable distance of up to 50 kilometers. At the same time, communication lines built on the use of optical fiber are practically insensitive to electromagnetic interference.
Where to "plug" the cable in the computer? You need an intermediate (interface) device, which is called a network card or network adapter, and in English speech NIC- Network Interface Controller.
, or NIC, is an embedded device that allows you to connect your computer to a network. Each computer has software installed that allows it to communicate with other computers.

Wireless communication on radio waves can be used to organize networks within large premises where the use of conventional communication lines is difficult or impractical. In addition, wireless lines can connect remote parts of the local network at distances up to 25 km (subject to line of sight).
In addition to cables and network adapters, twisted-pair LANs use other network devices such as hubs, switches, and routers.
concentrator(also called a hub) - a device that combines several (from 5 to 48) branches of a star-shaped local network and transmits information packets to all branches of the network in the same way.

(switch) does the same, but, unlike the hub, ensures the transfer of packets to the specified branches. This provides optimization of data flows in the network and increased security against unauthorized intrusion.

(router) - a device that transfers data between two networks, including between local and global networks. The router, in fact, is a specialized microcomputer, has its own processor, RAM and permanent memory, operating system.

interface device that connects two different types of networks. It receives the information, translates it into the required format, and then forwards the translation to its destination.

Shared External Devices include external memory drives connected to the server, printers, plotters and other equipment that becomes available from workstations.
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Organization transmission network data
A necessary condition for the operation of a single local area network is the use network operating system. Such operating systems ensure the sharing of not only network hardware resources (printers, drives, etc.), but also distributed collective technologies when performing a variety of jobs. The most widely used network operating systems NovellNetWare, linux And Windows.
Computers can communicate with each other because there are sets of rules, or protocols which help computers understand each other. Protocols are necessary for the communication process to proceed without errors. Protocols help define how information is sent and how it is received.

Why do we need local networks, and what are they? How to connect several computer devices to one Internet channel at once? What equipment is required to build a home network? You will receive answers to all these and other equally important questions in this material.

Introduction

Before you learn how to independently design and configure home local networks, let's immediately answer the most important question: "Why are they needed?".

By itself, the concept of a local network means combining several computers or computer devices into a single system for exchanging information between them, as well as sharing their computing resources and peripheral equipment. Thus, local networks allow:

Exchange data (movies, music, programs, games, etc.) between network members. At the same time, to watch movies or listen to music, it is absolutely not necessary to record them on your hard drive. The speeds of modern networks allow you to do this directly from a remote computer or multimedia device.

Connect simultaneously several devices to the global Internet through one access channel. This is probably one of the most requested features of local area networks, because today the list of equipment that can use a connection to the World Wide Web is very large. In addition to all kinds of computer equipment and mobile devices, TVs, DVD / Blu-Ray players, multimedia players and even all kinds of household appliances, from refrigerators to coffee makers, have now become full members of the network.

Sharing computer peripherals , such as printers, MFPs, scanners, and network attached storage (NAS).

Sharing the computing power of computers of network participants. When working with programs that require complex calculations, such as 3D visualization, you can use the free resources of other computers on the network to increase performance and speed up data processing. Thus, having several weak machines connected to a local network, you can use their total performance to perform resource-intensive tasks.

As you can see, creating a local network, even within the same apartment, can bring a lot of benefits. Moreover, the presence of several devices at once at home that require an Internet connection is not uncommon for a long time, and combining them into a common network is an urgent task for most users.

Basic principles of building a local network

Most often, local networks use two main types of data transfer between computers - by wire, such networks are called cable networks and use Ethernet technology, as well as using a radio signal over wireless networks built on the basis of the IEEE 802.11 standard, which is better known to users under the name Wi -Fi.

To date, wired networks still provide the highest throughput, allowing users to exchange information at speeds up to 100 Mbps (12 Mbps) or up to 1 Gbps (128 Mbps) depending on the equipment used (Fast Ethernet or Gigabit Ethernet). And although modern wireless technologies, purely theoretically, can also provide data transfer up to 1.3 Gb / s (Wi-Fi 802.11ac standard), in practice this figure looks much more modest and in most cases does not exceed 150 - 300 Mb / s. The reason for this is the high cost of high-speed Wi-Fi equipment and the low level of its use in current mobile devices.

As a rule, all modern home networks are arranged according to the same principle: user computers (workstations) equipped with network adapters are interconnected through special switching devices, which can be: routers (routers), switches (hubs or switches), points access or modems. We will talk in more detail about their differences and purposes below, but for now just know that without these electronic boxes, it will not work to combine several computers at once into one system. The maximum that can be achieved is to create a mini-network of two PCs by connecting them to each other.

At the very beginning, you need to determine the basic requirements for your future network and its scale. After all, the choice of the necessary equipment will directly depend on the number of devices, their physical placement and possible connection methods. Most often, a home local area network is combined and it can include several types of switching devices at once. For example, stationary computers can be connected to the network using wires, and various mobile devices (laptops, tablets, smartphones) can be connected via Wi-Fi.

For example, consider a diagram of one of the possible options for a home local network. It will involve electronic devices designed for different purposes and tasks, as well as using a different type of connection.

As can be seen from the figure, several desktop computers, laptops, smartphones, set-top boxes (IPTV), tablets and media players and other devices can be combined into a single network at once. Now let's figure out what kind of equipment you need to build your own network.

Network Card

A network card is a device that allows computers to communicate with each other and exchange data on a network. All network adapters by type can be divided into two large groups - wired and wireless. Wired network cards allow you to connect electronic devices to a network using Ethernet technology using a cable, and wireless network adapters use Wi-Fi radio technology.

As a rule, all modern desktop computers are already equipped with Ethernet network cards built into the motherboard, and all mobile devices (smartphones, tablets) are equipped with Wi-Fi network adapters. At the same time, laptops and ultrabooks are mostly equipped with both network interfaces at once.

Despite the fact that in the vast majority of cases, computer devices have built-in network interfaces, sometimes it becomes necessary to purchase additional boards, for example, to equip the system unit with a Wi-Fi wireless communication module.

According to their constructive implementation, individual network cards are divided into two groups - internal and external. Internal cards are designed to be installed in desktop computers using interfaces and their corresponding PCI and PCIe slots. External boards are connected via USB connectors or outdated PCMCIA (laptops only).

Router (Router)

The main and most important component of a home local network is a router or router - a special box that allows you to combine several electronic devices into a single network and connect them to the Internet through a single channel provided by your provider.

A router is a multifunctional device or even a minicomputer with its own built-in operating system that has at least two network interfaces. The first one is LAN (Local Area Network). ) or LAN (Local Area Network) is used to create an internal (home) network, which consists of your computer devices. The second - WAN (Wide Area Network) or WAN (Global Computing Network) is used to connect a local area network (LAN) to other networks and the World Wide Web - the Internet.

The main purpose of devices of this type is to determine the paths (routing) of data packets that the user sends to other, larger networks or requests from them. It is with the help of routers that huge networks are divided into many logical segments (subnets), one of which is the home LAN. Thus, at home, the main function of the router can be called the organization of the transfer of information from the local network to the global network, and vice versa.

Another important task of a router is to restrict access to your home network from the World Wide Web. Surely you are unlikely to be satisfied if anyone can connect to your computers and take or delete from them whatever they want. To prevent this from happening, the data flow intended for devices belonging to a specific subnet must not go beyond its limits. Therefore, the router from the total internal traffic generated by the members of the local network selects and sends to the global network only that information that is intended for other external subnets. This ensures the security of internal data and saves overall network bandwidth.

The main mechanism that allows the router to restrict or prevent access from the public network (outside) to devices on your local network is called NAT (Network Address Translation). It also provides all users of the home network with access to the Internet by converting several internal addresses of devices into one public external address provided by your Internet service provider. All this makes it possible for computers on the home network to easily exchange information with each other and receive it from other networks. At the same time, the data stored in them remains inaccessible to external users, although at any time access to them can be provided at your request.

In general, routers can be divided into two large groups - wired and wireless. Already by the names it is clear that all devices are connected to the first ones only with the help of cables, and to the second ones, both with the help of wires and without them using Wi-Fi technology. Therefore, at home, it is wireless routers that are most often used, which allow providing Internet and networking computer equipment using various communication technologies.

To connect computer devices using cables, the router has special sockets called ports. In most cases, the router has four LAN ports for connecting your devices and one WAN port for connecting an ISP cable.

In order not to overload the article with redundant information, we will not consider in detail the main technical characteristics of routers in this chapter, I will talk about them in a separate article, visited by choosing a router.

In many cases, the router may be the only component needed to build your own local network, as there will simply be no need for the rest. As we have already said, even the simplest router allows you to connect up to four computer devices using wires. Well, the number of equipment that receives simultaneous access to the network using Wi-Fi technology can even be in the tens, or even hundreds.

If, nevertheless, at some point the number of LAN ports of the router is no longer enough, then to expand the cable network, one or more switches can be connected to the router (we will discuss them below), which act as splitters.

Modem

In modern computer networks, a modem is a device that provides access to the Internet or access to other networks through ordinary wired telephone lines (xDSL class) or using wireless mobile technologies (3G class).

Conventionally, modems can be divided into two groups. The first includes those that connect to the computer via the USB interface and provide access to the network only one specific PC, to which the modem is directly connected. In the second group, LAN and / or Wi-Fi interfaces already familiar to us are used to connect to a computer. Their presence indicates that the modem has a built-in router. Such devices are often called combined, and they should be used to build a local network.

When choosing DSL equipment, users may encounter certain difficulties caused by confusion in its names. The fact is that often in the assortment of computer stores, two very similar classes of devices coexist at once: modems with built-in routers and routers with built-in modems. What is their difference?

There are practically no key differences between these two groups of devices. Manufacturers themselves position a router with a built-in modem as a more advanced option, endowed with a large number of additional functions and with improved performance. But if you are only interested in basic features, such as connecting all computers on a home network to the Internet, then there is not much difference between modem routers and routers where a DSL modem is used as an external network interface.

So, to summarize, a modern modem with which you can build a local network is, in fact, a router with an xDSL or 3G modem acting as an external network interface.

A switch or switch is used to connect various nodes of a computer network and exchange data between them via cables. The role of these nodes can be either separate devices, such as a desktop PC, or entire groups of devices already combined into an independent network segment. Unlike a router, the switch has only one network interface - LAN and is used at home as an auxiliary device, mainly for scaling local networks.

To connect computers using wires, like routers, switches also have special socket-ports. In models focused on home use, their number is usually five or eight. If at some point the number of switch ports is no longer enough to connect all devices, you can connect another switch to it. Thus, you can expand your home network as much as you like.

Switches are divided into two groups: managed and unmanaged. The first, as the name implies, can be controlled from the network using special software. With advanced functionality, they are expensive and not used in the home. Unmanaged switches distribute traffic and regulate the speed of data exchange between all network clients in automatic mode. It is these devices that are ideal solutions for building small and medium-sized local networks, where the number of participants in the exchange of information is small.

Depending on the model, the switches can provide a maximum data transfer rate of either 100 Mbps (Fast Ethernet) or 1000 Mbps (Gigabit Ethernet). Gigabit switches are best used for building home networks in which it is planned to frequently transfer large files between local devices.

Wireless access point

To provide wireless access to the Internet or local network resources, in addition to a wireless router, you can use another device called a wireless access point. Unlike a router, this station does not have an external WAN network interface and is equipped in most cases with only one LAN port for connecting to a router or switch. Thus, you will need an access point if your local network uses a regular router or modem without Wi-Fi support.

The use of additional access points in a network with a wireless router can be justified in cases where a large Wi-Fi coverage area is required. For example, the signal strength of a wireless router alone may not be enough to cover the entire area in a large office or a multi-storey country house.

Access points can also be used to organize wireless bridges that allow you to connect individual devices, network segments or entire networks using a radio signal in places where cabling is undesirable or difficult.

Network cable, connectors, sockets

Despite the rapid development of wireless technologies, many local networks are still built using wires. Such systems have high reliability, excellent throughput and minimize the possibility of unauthorized connections to your network from outside.

To create a wired local area network in home and office environments, Ethernet technology is used, where the signal is transmitted over the so-called "twisted pair" (TP-Twisted Pair) - a cable consisting of four copper twisted pairs of wires with each other (to reduce interference).

When building computer networks, mostly unshielded CAT5 cable is used, and more often its improved version CAT5e. Cables of this category allow you to transmit a signal at a speed of 100 Mbps when using only two pairs (half) of wires, and 1000 Mbps when using all four pairs.

To connect to devices (routers, switches, network cards, and so on), the ends of the twisted pair use 8-pin modular connectors, commonly referred to as RJ-45 (although their correct name is 8P8C).

Depending on your desire, you can either buy ready-made (with crimped connectors) network cables of a certain length, called “patch cords” in any computer store, or separately purchase twisted pair and connectors, and then make cables of the required size yourself in the right amount. How this is done, you will learn from a separate material.

Using cables to connect computers to a network, of course, you can connect them directly from switches or routers to connectors on PC network cards, but there is another option - using network sockets. In this case, one end of the cable is connected to the switch port, and the other to the internal contacts of the socket, in the external connector of which you can later connect computer or network devices.

Power outlets can be built into the wall or mounted outside. The use of sockets instead of protruding cable ends will give a more aesthetic look to your workplace. It is also convenient to use sockets as reference points for various network segments. For example, you can install a switch or router in the hallway of the apartment, and then from it thoroughly lay cables to sockets located in all necessary rooms. Thus, you will get several points located in different parts of the apartment, to which you can connect not only computers, but also any network devices at any time, for example, additional switches to expand your home or office network.

Another little thing that you may need when building a cable network is an extension cable, which can be used to connect two twisted pairs with already crimped RJ-45 connectors.

In addition to their direct purpose, extension cords are convenient to use in cases where the end of the cable ends with not one connector, but two. This option is possible when building networks with a bandwidth of 100 Mbps, where only two pairs of wires are sufficient to transmit a signal.

You can also use a network splitter to connect two computers to one cable at once without using a switch. But again, it is worth remembering that in this case the maximum data exchange rate will be limited to 100 Mbps.

Read more about twisted pair crimping, connecting sockets and the characteristics of network cables in a special material.

Now that we've seen the basic components of a LAN, it's time to talk about topology. In simple terms, a network topology is a diagram that describes the locations and how network devices are connected.

There are three main types of network topology: Bus, Ring, and Star. With a bus topology, all computers on the network are connected to one common cable. To combine PCs into a single network using the "Ring" topology, they are serially connected to each other, while the last computer is connected to the first. With a star topology, each device is connected to the network through a special hub using a separate cable.

Probably, the attentive reader has already guessed that to build a home or small office network, the Star topology is mainly used, where routers and switches are used as hub devices.

Creating a network using the Zvezda topology does not require deep technical knowledge and large financial investments. For example, using a switch that costs 250 rubles, you can network 5 computers in a few minutes, and using a router for a couple of thousand rubles, you can even build a home network, providing several dozen devices with access to the Internet and local resources.

Another undoubted advantage of this topology is good scalability and ease of upgrade. Thus, network branching and scaling is achieved by simply adding additional hubs with the necessary functionality. Also, at any time, you can change the physical location of network devices or swap them in order to achieve more practical use of equipment and reduce the number and length of connecting wires.

Despite the fact that the Zvezda topology allows you to quickly change the network structure, the location of the router, switches and other necessary elements must be thought out in advance, in accordance with the layout of the room, the number of connected devices and how they are connected to the network. This will minimize the risks associated with the purchase of unsuitable or redundant equipment and optimize the amount of your financial costs.

Conclusion

In this material, we examined the general principles of building local networks, the main equipment that is used and its purpose. Now you know that the main element of almost any home network is a router, which allows you to network many devices using both wired (Ethernet) and wireless (Wi-Fi) technologies, while providing all of them with an Internet connection through one single channel.

Switches are used as ancillary equipment to expand the points of connection to the local network using cables, which are essentially splitters. To organize wireless connections, access points are used, which allow using Wi-Fi technology not only to connect all kinds of devices wirelessly to the network, but also in the "bridge" mode to connect entire segments of the local network.

In order to understand exactly how much and what kind of equipment you will need to purchase to create a future home network, be sure to first draw up its topology. Draw a diagram of the location of all network member devices that will need a cable connection. Depending on this, select the optimal location for the router and, if necessary, additional switches. There are no uniform rules here, since the physical location of the router and switches depends on many factors: the number and type of devices, as well as the tasks that will be assigned to them; the layout and size of the room; requirements for the aesthetics of the type of switching nodes; possibilities for laying cables and others.

So, as soon as you have a detailed plan for your future network, you can begin to move on to the selection and purchase of the necessary equipment, its installation and configuration. But we will talk about these topics in our next materials.

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Topic: Combining computers into a local computer network. Organization of work of users in local computer networks. Compiled by: teacher of the SMT FSBEI HE "Kerch State Marine Technological University" Sharatova Natalya Vladimirovna

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A computer network is a collection of computers connected to each other using special equipment, which ensures the exchange of information between the computers of this group and is equipped with special communication software.

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Networks provide users with the opportunity not only to quickly exchange information, but also to collaborate on printers and other peripheral devices, and even to process documents simultaneously.

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The main characteristics of networks include: Bandwidth - the maximum amount of data transmitted by the network per unit of time. Throughput is measured in Mbps. Network response time - the time spent by the software and network devices to prepare for the transmission of information over a given channel. Network response time is measured in milliseconds.

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Computers can communicate with each other because there are sets of rules, or protocols, that help computers understand each other. Protocols are necessary for the communication process to proceed without errors. Protocols help define how information is sent and how it is received. A network protocol is a set of rules for organizing work on a computer network.

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Local area network (LAN - Local Area Network) - a network within an enterprise, institution, one organization. Regional network (MAN - Metropolitan Area Network) - a network within a city or region. Wide area network (WAN - Wide Area Network) - a network on the territory of a state or a group of states.

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A workstation (client-machine, workplace, subscriber station, terminal) is a computer that is directly used by a computer network subscriber. The network of workstations is represented by a set of workstations and means of communication that ensure the interaction of workstations with the server and with each other.

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A server is a computer that performs general computer network tasks and provides services to workstations. A server network is a collection of servers and communications that connect servers to the underlying data network.

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The underlying data communication network is a collection of means for transmitting data between servers. It consists of communication channels and communication nodes.

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A communication node is a set of means of switching and data transmission in one point. The communication node receives the data coming through the communication channels and transmits the data to the channels leading to the subscribers.

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A local area network is a system of interconnected computers operating within the same premises, building, or one organization. Local computer networks

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quick exchange of information sharing of peripheral devices (printer, scanner, modem, etc.) simultaneous work with documents Based on the distribution of functions, local computer networks are divided into peer-to-peer and multi-rank

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In a peer-to-peer network, all computers are equal. Peer-to-peer networks are also called workgroups. A workgroup is a small team, so peer-to-peer networks often have no more than 10 computers. Types of LANs A dedicated server is a server that functions only as a server (excluding client or workstation functions). Peer-to-peer network Dedicated server network

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server-based peer-to-peer Computers are peers. Users independently decide which computer resources to make public. A computer used as a repository of shared information resources and allowing connection to shared technical devices. The local network

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Peer-to-peer network Computers in such a network are equal in relation to each other. Each user on the network decides for himself what resources of his computer he will provide for general use. The computer acts as both a client and a server.

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Server (from the English server - service device) - a computer that distributes resources between network users, used as a repository of shared information resources and allows you to connect to technical devices for general access.

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 The server can provide various services, of which the following are the most well-known: storage and provision of files (file server); output to a printer (print server); receiving and forwarding fax messages (fax server); receipt, storage and transmission of e-mail messages (mail server); site hosting (web-server).

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Topology "Bus" A single cable is used along which all computers in the network are connected. The terminator is needed to absorb the transmitted signal at the ends. Simplicity If one computer fails, it will not affect the operation of the others Only one computer can transmit data at a time Breaking the cable causes the network to stop working When a large number of computers, the network is slow terminator terminator

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Tire. A communication channel that connects nodes into a network forms a broken line - a bus. Any node can receive information at any time, and transmit only when the bus is free. Data (signals) are transmitted by the computer to the bus. Each computer checks them, determining to whom the information is addressed, and accepts the data if they are sent to it, or ignores it. If the computers are located close to each other, then the organization of a CS with a bus topology is inexpensive and simple - you just need to lay a cable from one computer to another. Signal attenuation with increasing distance limits the length of the bus, and therefore the number of computers connected to it. Bus topology problems arise - when there is a break (disruption of contacts) at any point in the country; the network adapter of one of the computers fails and starts transmitting interference signals to the bus; you need to connect a new computer.

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Topology "Ring" Signals travel around the ring in one direction and pass through each computer (closed network). The cable has no free end and therefore no terminator is needed Each computer amplifies the signals by passing them on to the next computer If one computer fails, the entire network stops functioning

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Ring. The nodes are connected in a network of a closed curve. Data is transmitted in only one direction. Each node, among other things, implements the functions of a relay. He receives and transmits messages, and perceives only addressed to him. Using ring topology, you can connect a large number of nodes to the network, solving the problems of interference and signal attenuation using the network card of each node. Disadvantages of the ring organization: a break anywhere in the ring stops the entire network; the transmission time of the message is determined by the successive operation time of each node located between the sender and the recipient of the message; due to the passage of data through each node, there is the possibility of inadvertent distortion of information.

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Topology "Star" Server Network management is centralized (there is a special central device (hub), from which "beams" go to each computer, i.e. each computer is connected to its own cable). If one computer fails, the network remains operational For large networks, cable consumption increases significantly If the server fails, the network stops functioning

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Star. Network nodes are connected to the center by beams. All information is transmitted through the center, which makes it relatively easy to troubleshoot and add new nodes without interrupting the network. However, the cost of organizing communication channels is usually higher here than for a bus and a ring.

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Topology "Tree" A hierarchical connection of nodes emanating from a common root node. There is only one route between any two nodes. high efficiency of use; the failure of one station or cable will not affect the operation of others; saving working time. a large amount of cable is required; reliability and performance is determined by the central node.

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The combination of basic topologies - hybrid topology - provides a wide range of solutions that accumulate the advantages and disadvantages of the basic ones. In addition to the problems of creating local computer networks, there is also the problem of expanding (combining) computer networks. The fact is that a computer network created at a certain stage in the development of an information system may eventually cease to satisfy the needs of all users. At the same time, the physical properties of the signal, data transmission channels, and design features of network components impose severe restrictions on the number of nodes and the geometric dimensions of the network.

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Network hardware To organize a local network, you need to install a network card in each PC and connect all computers using a special cable.

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A network adapter is a device required to connect a computer to a local network. Each network adapter has a unique internal number, the so-called MAC address, which allows you to uniquely identify the source of information in the network environment.

31 slide

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Network boards are characterized by: Bit depth: 8 bits, 16 bits and 32 bits. The data bus through which information is exchanged between the motherboard and the network card: ISA, EISA, VL-Bus, PCI, etc. The controller chip on which this board is made. Supported network transmission medium. Operating speed: Ethernet 10Mbit and / or Fast Ethernet 100Mbit, Gigabit Ethernet 1000Base-T. MAC address

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The network adapter is attached to the cable using special connectors, the type of which depends on the type of cable. For example, for a twisted pair cable, an RG-45 type connector is used, which looks like a phone jack. There are network adapters that use the wireless principle of interaction. At present, the three main types of wireless data transmission are radio, microwave, and infrared. The most common, at present, option for organizing a wireless local area network is the use of WiFi equipment.

34 slide

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Each 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.

35 slide

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Hardware equipment of computer networks Transmission medium Information can be transmitted using physical signals of various nature. These can be electrical signals, electromagnetic radiation, optical signals. Depending on the type of signal, different transmission media are used - wired or wireless. The transmission medium is a physical medium in which the transmission of information signals in the form of electrical, light and other impulses is possible.

36 slide

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Wireless environment Wired environment In wired environments, computers and other network devices are connected by cables, such as copper (twisted pair, coaxial cable) or fiber optic cables. The data is transmitted in the form of electrical or optical signals. television and radio satellite communications

37 slide

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Coaxial cable - transmission speed up to 10 Mbps Twisted pair - transmission speed up to 100 Mbps Cable types Fiber optic cable - transmission of information over long distances

38 slide

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Network cables Twisted pair cables are one of the components of modern structured cabling systems. It is used in telecommunications and computer networks as a physical signal transmission medium in many technologies such as Ethernet, Arcnet and Token ring. Currently, due to its low cost and ease of installation, it is the most common solution for building wired (cable) local networks.

39 slide

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The simplest design of a coaxial cable includes a copper core enclosed in insulation, a metal shield braid and an outer sheath. In some modifications, an additional layer of foil is present, which means double shielding. The strongest interference is overcome by cables containing four screenings, including two layers of foil and two layers of metal braid. Network cables

40 slide

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fiber optic cable. In a fiber optic cable, digital data is propagated by optical fibers in the form of modulated light pulses. This is a relatively secure transmission method because it does not use electrical signals. So, it is impossible to connect to a fiber optic cable without destroying it and intercept data, which is not immune to any cable that conducts electrical signals. Fiber optic lines are designed to transmit large amounts of data at very high speeds, since the signal in them is practically not attenuated or distorted. An optical fiber is an extremely thin glass cylinder called a core. It is covered with a layer of glass (sheath) with a different refractive index than that of the core. Sometimes optical fiber is made of plastic. Plastic is easier to install, but it transmits light pulses over shorter distances compared to glass fiber. Each fiber only transmits signals in one direction, so the cable consists of two fibers with separate connectors. One of them is for transmitting and the other for receiving. The rigidity of the cable is increased by a plastic coating, and the strength is increased by Kevlar fibers. Network cables

41 slide

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Transmission medium Wireless medium Characteristics of the transmission medium In wireless environments, cables are not used, and data is transmitted over the air, usually in the form of radio signals. One of the main characteristics of the transmission medium is the data transfer rate, which is measured in: bits per second (bps), kilobits per second (Kbps), megabits per second (Mbps) and gigabits per second (Gbps) . The data transfer rate in computer networks is defined as the number of bits transmitted through a certain medium per unit of time.

42 slide

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Wireless connection Uses airborne radio channel; this is convenient as no wiring is required, but more expensive than wired connections Wireless connection

43 slide

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Network interfaces In order for a computer or other device to be connected to a local network, it must be equipped with a network interface (network card) to which a network cable is connected or which will provide communication via a radio channel. Network interfaces are made in the form of boards. A network interface is a piece of equipment designed to connect a computer or other device on a local area network.

44 slide

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45 slide

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Modems A modem is a device used to connect computers to global networks To connect individual computers and local networks to the global Internet, telephone, cable television networks, and satellite mobile communications can be used. The parameters of the signals transmitted by these communication channels and the signals used in local networks and in the computer itself are different. Therefore, to connect to the global network, a special device is required - a modem. Depending on which communication channel the modem is assigned to, there are modems for telephone lines, television cable lines, satellite modems, modems for mobile communications. Modems are available as stand-alone devices and as boards that plug into slots on the motherboard.

46 slide

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* Modems analog signals digital codes digital codes 101001101 A modem is a device for connecting two computers using a telephone line. Modem (modulator / demodulator) - a device for converting an analog signal into a digital code and vice versa. Exchange rate (bits per second): reception up to 56 Kbps transmission up to 33 Kbps 101001101 modem modem

47 slide

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48 slide

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Modems Modem CMOTECH High speed wireless modem One of the first usb modems for using mobile Internet.

49 slide

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Modems Thrane Satellite Modem Thrane Explorer 700 TV Cable Modems

50 slide

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Modems Modems for mobile calls Modems for telephone lines

51 slide

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A simple local area network (LAN - Local Area Network) with Internet access consists of network adapters (installed in computers) that are connected to a hub or switch, which in turn is connected to a router. Currently, in the vast majority of cases, Ethernet technology is used to build LAN networks in an office or at home, and twisted pair is used as a network cable.

52 slide

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Hubs, Switches, and Wireless Access Points To implement a "star" network topology, you need a device to which all network computers will connect and which will provide data exchange between them. The function of such "central" devices can be performed by hubs and switches. A hub is a device that transmits received data to all devices connected to it. A switch is a device that determines to whom the received data is addressed, and therefore sends them not to all devices, but only to the recipient. To create wireless networks, wireless access points are used, which function in the same way as hubs.

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_1.jpg" alt="(!LANG:>Connecting computers to a local network. Organization of user work in local computer networks . Performed:"> Объединение компьютеров в локальную сеть. Организация работы пользователей в локальных компьютерных сетях. Выполнила: Преподаватель ГБОУ СПО «Самарский техникум кулинарного искусства» Иванова Н.Б.!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_2.jpg" alt="(!LANG:>A computer network is a connection between computers to exchange information and share resources ( printer, modem,"> Компьютерная сеть – соединение компьютеров для обмена информацией и совместного использования ресурсов (принтер, модем, дисковая память и т.д.).!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_3.jpg" alt="(!LANG:>Local Area Network"> Локальная сеть Локальная сеть объединяет компьютеры установленные в одном помещении (учебный класс, офис и т.п.), в одном здании или в нескольких близко расположенных зданиях. Обычно компьютеры локальной сети расположены на расстоянии не более одного километра. При увеличении расстояния используется специальное оборудование.!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_4.jpg" alt="(!LANG:>Local networks are divided into: peer-to-peer; networks"> Локальные сети по способу взаимодействия компьютеров подразделяются на: одноранговые; сети с выделенным сервером.!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_5.jpg" alt="(!LANG:>Client is a task, workstation or computer network user. In progress customer data processing"> Клиент - задача, рабочая станция или пользователь компьютерной сети. В процессе обработки данных клиент может сформировать запрос на сервер для выполнения сложных процедур, чтения файлов, поиск информации в базе данных и т.д. Сервер, определенный ранее, выполняет запрос, поступивший от клиента. Результаты выполнения запроса передаются клиенту. Сервер обеспечивает хранение данных общего пользования, организует доступ к этим данным и передает данные клиенту.!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_6.jpg" alt="(!LANG:>Peer-to-Peer LAN In a peer-to-peer LAN, all computers are peers. Shared devices may"> Одноранговая локальная сеть В одноранговой локальной сети все компьютеры равноправны. Общие устройства могут быть подключены к любому компьютеру в сети.!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_7.jpg" alt="(!LANG:>Advantages of peer-to-peer networks: low cost; high reliability. Disadvantages peer-to-peer networks:"> Достоинства одноранговых сетей: · низкая стоимость; · высокая надежность. Недостатки одноранговых сетей: · зависимость эффективности работы сети от количества станций; · сложность управления сетью; · сложность обеспечения защиты информации; · трудности обновления и изменения программного обеспечения станций!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_8.jpg" alt="(!LANG:>Dedicated server network Dedicated server network structure">!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_9.jpg" alt="(!LANG:>Network with dedicated server Server ) is a computer distributing"> Сеть с выделенным сервером Сервер (от англ. server - обслуживающее устройство) - компьютер, распределяющий ресурсы между пользователями сети. В сервере установлен мощный процессор, большая оперативная и дисковая память, хранится основная часть программного обеспечения и данных сети, которыми могут воспользоваться все пользователи сети.!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_10.jpg" alt="(!LANG:>Network with a dedicated server"> Сеть с выделенным сервером В качестве рабочих станций обычно используются менее производительные компьютеры с меньшей дисковой и оперативной памятью.!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_11.jpg" alt="(!LANG:>In networks with a dedicated server, client-server technology is implemented. On the server server software is installed:"> В сетях с выделенным сервером реализуется клиент-серверная технология. На сервере устанавливается серверное ПО: серверная операционная система; WEB-сервер (организация Интранет); прокси-сервер (обеспечение работы с Интернет рабочих станций); файл-сервер (обеспечение совместного доступа к файлам) и т.п. ПО сетей с выделенным сервером!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_12.jpg" alt="(!LANG:>Client software is installed on the workstation: operating system for workstations;"> На рабочей станции устанавливается клиентское ПО: операционная система для рабочих станций; клиентская часть прикладного ПО и т.п. ПО сетей с выделенным сервером!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_13.jpg" alt="(!LANG:> peer-to-peer networks);"> Наиболее распространены следующие способы соединения компьютеров: шина (как правило используется для одноранговых сетей); звезда (используется для любых локальных сетей). Аппаратное обеспечение сети!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_14.jpg" alt="(!LANG:>Connection type - "bus" The cable runs from one computer to another connecting computers and"> Тип соединения - «шина» Кабель проходит от одного компьютера к другому, соединяя компьютеры и периферийные устройства!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_15.jpg" alt="(!LANG:>Star connection type one central node.">!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_16.jpg" alt="(!LANG:>LAN Components"> Компоненты локальной сети Для организации локальной сети необходимо установить в каждый ПК сетевую плату и соединить все компьютеры с помощью специального кабеля.!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_17.jpg" alt="(!LANG:>LAN Components Sometimes the components necessary for connecting computers are already installed"> Компоненты локальной сети Иногда необходимые для связи компьютеров компоненты уже установлены на системной плате и тогда отдельная сетевая плата не нужна. В этом случае гнездо для сетевого кабеля расположено на задней стенке системного блока.!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_18.jpg" alt="(!LANG:>LAN Components Cables Coaxial cable - transmission rate up to 10 Mbps/ C. Twisted pair"> Компоненты локальной сети Кабели Коаксиальный кабель – скорость передачи до 10 Мбит/с. Витая пара - скорость передачи до 100 Мбит/с.!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_19.jpg" alt="(!LANG:>LAN Components Cable Connectors for Twisted Pair Coaxial Cable">!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_20.jpg" alt="(!LANG:>LAN Components Hubs (HUB or Switch) - serve"> Компоненты локальной сети Концентраторы (HUB или Switch) - служат для соединения компьютеров в сети. Концентратор может иметь различное количество портов подключения (обычно от 8 до 32).!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_21.jpg" alt="(!LANG:>LAN Components The overall network connection speed when using the HUB is determined by the speed"> Компоненты локальной сети Общая скорость соединения в сети при использовании HUB определяется скоростью самой медленной сетевой платы. Для Switch скорость соединения любой пары компьютеров определяется скоростью самой медленной сетевой платы в паре (группе).!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_22.jpg" alt="(!LANG:>Network software For LAN operation"> Программное обеспечение сети Для работы в локальной сети необходимо специальное сетевое программное обеспечение. В операционной системе Windows уже имеется всё необходимое для установки сети.!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_23.jpg" alt="(!LANG:>Network software ;"> Программное обеспечение сети Для организации локальной сети необходимо: определить имя Рабочей группы; присвоить каждому компьютеру уникальное в данной Рабочей группе имя и IP-адрес, а также установить адрес маски подсети (в некоторых случаях явный IP-адрес и адрес маски подсети можно не устанавливать).!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_24.jpg" alt="(!LANG:>Network Software This window is used to set the computer name and"> Программное обеспечение сети Данное окно используется для установки имени компьютера и Рабочей группы!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_25.jpg" alt="(!LANG:>Network Software These windows are used to set the explicit IP address and subnet mask settings">!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_26.jpg" alt="(!LANG:>This window is used to set the level of access to local computer resources"> Данное окно используется для установки уровня доступа к локальным ресурсам компьютера Режимы доступа к ресурсам сети!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_27.jpg" alt="(!LANG:>Local resource. Network users are denied access to computer resources. To ensure availability of local resources"> Локальный ресурс. Запрещается доступ к ресурсам компьютера пользователям сети. Для обеспечения доступности локальных ресурсов нужно установить переключатель в положение Общий ресурс. Общий ресурс. Позволяет использовать ресурсы компьютера (дисковую память и периферийные устройства - принтер, модем) пользователям сети. Для этого, нужно разрешить Открытие общего доступа к папке. При этом требуется определить уровень доступа. Режимы доступа к ресурсам сети!}

Src="https://present5.com/presentacii-2/20171208%5C3432-lokalnaya_set.ppt%5C3432-lokalnaya_set_28.jpg" alt="(!LANG:>Network Access Modes Read only Allows network users to open or copy files"> Режимы доступа к ресурсам сети Только чтение Позволяет пользователям сети открывать или копировать файлы и папки. Полный доступ Позволяет пользователям сети выполнять все операции над файлами, папками (переносить, удалять, редактировать, переименовать и т.п.). Доступ, определяемый паролем Данный режим предоставляет разным категориям пользователей различные права доступа, например, только чтение или полный доступ.!}

Plan

Purpose of local networks.

Are there any ways to connect devices?

Star topologies

Bus topologies

Ring topologies

The main devices for the rapid transmission of information over long distances are currently the telegraph, radio, telephone, television transmitter, and telecommunication networks based on computer systems.

The transfer of information between computers has existed since the very beginning of the computer. It allows you to organize the joint work of individual computers, solve one problem with the help of several computers, and solve many other problems.

Under computer network understand the complex of hardware and software designed for the exchange of information and user access to common network resources.

The main purpose of computer networks - provide users with joint access to information (databases, documents, etc.) and resources (hard drives, printers, access to the global network, etc.).

Network subscribers - objects that generate or consume information.

Any subscriber of the network is connected to the station.

Station – equipment that performs functions related to the transmission and reception of information.

To organize the interaction of subscribers and the station, a physical transmission medium is needed.

Physical transmission medium – communication lines or space in which electrical signals propagate and data transmission equipment.

One of the main characteristics of lines or communication channels is the data transfer rate (bandwidth).

Transfer rate - the number of bits of information transmitted per unit of time.

Typically, data transfer rates are measured in bits per second (bps) and multiples of Kbps and Mbps.

A communication network is built on the basis of the physical transmission medium. Thus, a computer network is a combination of subscriber systems and a communication network.

Types of networks.

According to the type of computers usedhomogeneous Andheterogeneous networks . Heterogeneous networks contain software-incompatible computers, while homogeneous networks contain vice versa.

On a territorial basis, networks are divided intolocal And global.

Local networks (LAN, Local Area Network) unite subscribers located within a small area, no more than 2–2.5 km.

Local computer networks will make it possible to organize the work of individual enterprises and institutions, including educational ones, to solve the problem of organizing access to common technical and information resources.

global networks (WAN, Wide Area Network)unite subscribers located at considerable distances from each other: in different parts of the city, in different cities, countries, on different continents (for example, the Internet).

Interaction between subscribers of such a network can be carried out on the basis of telephone lines, radio communications and satellite communications systems. Global computer networks will solve the problem of combining the information resources of all mankind and organizing access to these resources.

Main communication network components :

transmitter;

receiver;

messages (text or image);

means of transmission (physical transmission medium and special equipment that ensures the transmission of information).

Topology of local networks.

Undercomputer network topology usually understand the physical location of network computers relative to each other and the way they are connected by lines.

The topology determines the requirements for the equipment, the type of cable used, the methods of managing the exchange, the reliability of operation, and the possibility of expanding the network.

There are three main types of network topology:

tire, star and ring.

Bus , in which all computers are connected in parallel to one communication line, and information from each computer is simultaneously transmitted to all other computers.

Star (star) , in which other peripheral computers are connected to one central computer, each of them using its own separate communication line. The entire exchange of information goes exclusively through the central computer, which bears a very heavy load, so it is intended only for servicing the network.

ring , in which each computer always transmits information to only one computer, the next in the chain, and receives information only from the previous computer in the chain, and this chain is closed. A feature of the ring is that each computer restores the signal coming to it, so the attenuation of the signal in the entire ring does not matter, only the attenuation between neighboring computers is important.

The concept of global networks

Global network - these are associations of computers located at a remote distance for the general use of world information resources, the most popular is the Internet.

Usually, computers operating according to different rules (having different architecture, system software, etc.) are combined in a global network. Therefore, to transfer information from one type of network to another,gateways.

Gateways - these are devices (computers) that serve to combine networks with completely different exchange protocols.

Exchange protocol - it is a set of rules (agreement, standard) that defines the principles for exchanging data between different computers on a network.

The protocols are conditionally divided into basic (lower level), responsible for the transfer of information of any type, and application (higher level), responsible for the functioning of specialized services.

The network host that provides access to a common database, I/O device sharing, and user interaction is called server .

A network computer that only uses network resources, but does not give its own resources to the network, is called. To work in the global network, the user must have the appropriate hardware and software.

test questions

What are local networks?

What are the ways to connect devices?

Pros and Cons of Star Topology

Pros and cons of bus topology

Pros and Cons of Ring Topology