LAN equipment. Local computer network: design and network equipment Equipment in a local computer network

LAN equipment is a complex of components that have different purposes, but are closely interconnected, ensuring high performance and uninterrupted functioning of networks. LAN equipment can be divided into the following functional groups:

• active equipment (hubs, switches, routers, etc.)
• passive equipment (cables, mounting cabinets, distribution boards, cable ducts, patch panels, information sockets)
• computer equipment (servers, PCs)
• peripheral equipment (printers, scanners, faxes, etc.)

Active LAN equipment, its types, purpose and place in the general list of LAN equipment

Active LAN equipment is the basis of the network and contains the following main types of devices:

• network interface cards
• hubs
• repeaters
• bridges
• routers
• switches

Network interface cards are sometimes called network cards or adapters and are devices for organizing a network interface on work nodes (computers).

Repeaters serve to amplify the signal transmitted through the cable and are practically not used in their pure form: their functions have been completely taken over by concentrators. The only difference between a classic hub is the number of ports: from 5 to 16 or more versus the two ports found in repeaters.

A bridge is most often used in cases where it is necessary to differentiate data transmission for different logical parts of the network. Another purpose of bridges is to connect networks with different data transfer rates.

The switch, in turn, copied all the functions of the bridge, hub and repeater combined, adding to them many additional “conveniences”, including, for example, the ability to create logical groups of ports in order to organize independent virtual networks within one switch.

Routers belong to active LAN equipment, which, like repeaters, are practically not used in modern local networks. Routers, however, serve to connect different LANs into a common network via wide-area links or the Internet.

One way or another, the choice of LAN equipment - both active and passive - is determined by the Customer’s requirements for the network, its scale and development prospects, as well as the class of computer and peripheral equipment already available at the site and other factors. That is why the use and interaction of certain devices is individual for each specific network.

Highly qualified engineers of the Flylink company with extensive experience will select the most suitable active LAN equipment, and on its basis a high-performance, reliable, hacker-resistant and durable information infrastructure. Thus, you will find an invisible but ideal assistant for doing business.

Open Systems Interconnection Model

Network topology

When two or more computers are physically connected, a computer network. In general, to create computer networks you need special hardware - network equipment and special software - network software.

Already, there are areas of human activity that fundamentally cannot exist without networks (for example, the work of banks, large libraries, etc. Networks are also used in the management of large automated industries, gas pipelines, power plants, etc. Computers use a wide variety of data transfer physical channels, which are usually called transmission medium.

The purpose of all types of computer networks is determined by two functions:

· ensuring the sharing of hardware and software network resources;

· providing shared access to data resources.

For example, all participants in a local network can share one common printing device - a network printer or, for example, the hard drive resources of one dedicated computer - a file server. Software can be shared in the same way. If there is a special computer on a network that is dedicated to shared use by network participants, it is called file server.

Groups of employees working on one project within a local network are called working groups. Several workgroups can operate within the same local network. Team members may have different rights to access shared network resources. A set of techniques for separating and limiting the rights of participants in a computer network is called network policy. Network policy management is called network administration. A person who manages the organization of work of participants in a local computer network is called system administrator

1.1. Basic characteristics and classification of computer networks

By territorial distribution networks can be local, global, and regional.

The local network(LAN - Local Area Network) - a network within an enterprise, institution, or one organization.

Regional network(MAN - Metropolitan Area Network) - a network within a city or region.

Global network(WAN - Wide Area Network) – a network on the territory of a state or group of states.

By information transfer speed computer networks are divided into low-, medium- and high-speed:

· low speed networks - up to 10 Mbit/s;

· medium speed networks - up to 100 Mbit/s;

· high speed networks - over 100 Mbit/s.

Based on the type of transmission medium, networks are divided into:

· wired(coaxial cable, twisted pair, fiber optic);

· wireless with the transmission of information via radio channels or in the infrared range.

According to the method of organizing the interaction of computers, networks are divided into peer-to-peer And with dedicated server (hierarchical networks).

All computers in a peer-to-peer network have equal rights. Any network user can access data stored on any computer.

The main advantage of peer-to-peer networks is the ease of installation and operation. The main disadvantage is that in peer-to-peer networks it is difficult to resolve information security issues. Therefore, this method of organizing a network is used for networks with a small number of computers and where the issue of data protection is not fundamental.

In a hierarchical network, when setting up the network, one or more servers- computers that manage data exchange over the network and resource distribution. Any computer that has access to the server's services is called network client or workstation.

A server in hierarchical networks is a permanent storage of shared resources. The server itself can only be a client of a server at a higher hierarchy level. Servers are typically high-performance computers, possibly with multiple parallel processors, high-capacity hard drives, and a high-speed network card.

The hierarchical network model is the most preferable, as it allows you to create the most stable network structure and more rationally distribute resources. Another advantage of a hierarchical network is a higher level of data protection. The disadvantages of a hierarchical network, compared to peer-to-peer networks, include:

1. The need for an additional OS for the server.

2. Higher complexity of network installation and upgrades.

3. The need to allocate a separate computer as a server

Based on server technology distinguish networks with architecture file-server and networks with architecture client-server. The first model uses a file server on which most programs and data are stored. At the user's request, the necessary program and data are sent to him. Information processing is performed at the workstation.

In systems with a client-server architecture, data is exchanged between a client application and a server application. Data is stored and processed on a powerful server, which also controls access to resources and data. The workstation receives only the query results.

The main characteristics of networks include:

Bandwidth– the maximum amount of data transmitted by the network per unit of time. Bandwidth is measured in Mbit/s.

Network response time- time spent by software and network devices to prepare for transmitting information over a given channel. Network response time is measured in milliseconds.

1.2. Network topology

Network topology refers to the physical or electrical configuration of the network's cabling and connections. Several specialized terms are used in network topology:

· network node - computer or network switching device;

· network branch - a path connecting two adjacent nodes;

· terminal node - a node located at the end of only one branch;

· intermediate node - a node located at the ends of more than one branch;

· adjacent nodes are nodes connected by at least one path that does not contain any other nodes.

There are only 5 main types of network topologies:

1. “Shared Bus” topology. In this case, the connection and data exchange is carried out through a common communication channel called a common bus:

The public bus is a very common topology for local area networks. The transmitted information can be distributed in both directions. The use of a common bus reduces wiring costs and unifies the connection of various modules. The main advantages of this scheme are the low cost and ease of cable distribution throughout the premises. The most serious disadvantage of the common bus is its low reliability: any defect in the cable or any of the numerous connectors completely paralyzes the entire network. Another disadvantage of the shared bus is its low performance, since with this connection method only one computer at a time can transmit data to the network. Therefore, the communication channel bandwidth is always divided here between all network nodes.

2. Star topology. In this case, each computer is connected with a separate cable to a common device called hub, which is located in the center of the network:

The function of a hub is to direct information transmitted by a computer to one or all other computers on the network. The main advantage of this topology over a common bus is significantly greater reliability. Any problems with the cable affect only the computer to which this cable is connected, and only a malfunction of the hub can bring down the entire network. In addition, the hub can play the role of an intelligent filter of information coming from nodes on the network and, if necessary, block transmissions prohibited by the administrator.

The disadvantages of a star topology include the higher cost of network equipment due to the need to purchase a hub. In addition, the ability to increase the number of nodes in the network is limited by the number of hub ports. Currently, a hierarchical star is the most common type of connection topology in both local and global networks.

3. “Ring” topology. In networks with a ring topology, data in the network is transmitted sequentially from one station to another along the ring, usually in one direction:

If the computer recognizes the data as intended for it, then it copies it to its internal buffer. In a network with a ring topology, it is necessary to take special measures so that in the event of a failure or disconnection of any station, the communication channel between the remaining stations is not interrupted. The advantage of this topology is ease of management, the disadvantage is the possibility of failure of the entire network if there is a failure in the channel between two nodes.

4. Mesh topology. The mesh topology is characterized by a computer connection scheme in which physical communication lines are established with all nearby computers:

In a network with a mesh topology, only those computers between which intensive data exchange occurs are directly connected, and for data exchange between computers that are not directly connected, transit transmissions through intermediate nodes are used. The mesh topology allows the connection of a large number of computers and is typically characteristic of global networks. The advantages of this topology are its resistance to failures and overloads, because There are several ways to bypass individual nodes.

5. Mixed topology. While small networks typically have a typical star, ring, or bus topology, large networks typically have random connections between computers. In such networks, individual subnetworks with a standard topology can be identified, which is why they are called networks with mixed topology:

1.3. Open Systems Interconnection Model

The main task solved when creating computer networks is to ensure compatibility of equipment in terms of electrical and mechanical characteristics and ensure compatibility of information support (programs and data) in terms of coding system and data format. The solution to this problem belongs to the field of standardization and is based on the so-called OSI models(Model of Open System Interconnections). The OSI model was created based on technical proposals from the International Standards Organization (ISO).

According to the OSI model, the architecture of computer networks should be considered at different levels (the total number of levels is up to seven). The highest level is applied. At this level the user interacts with the computing system. The lowest level is physical. It ensures the exchange of signals between devices. Data exchange in communication systems occurs by moving it from the upper level to the lower one, then transporting it and, finally, playing it back on the client's computer as a result of moving from the lower level to the upper one.

To ensure the necessary compatibility at each of the seven possible levels of computer network architecture, there are special standards called protocols. They determine the nature of the hardware interaction of network components ( hardware protocols) and the nature of the interaction between programs and data ( software protocols). Physically, protocol support functions are performed by hardware devices ( interfaces) and software (protocol support programs). Programs that support protocols are also called protocols.

Each level of the architecture is divided into two parts:

Service specification;

Protocol specification.

A service specification defines what a layer does, and a protocol specification defines how it does it, and any given layer may have more than one protocol.

Let's look at the functions performed by each layer of software:

1. Physical layer makes connections to a physical channel, disconnects from a channel, and controls the channel. The data transfer rate and network topology are determined.

2. Link layer adds auxiliary characters to the transmitted arrays of information and controls the correctness of the transmitted data. Here the transmitted information is divided into several packets or frames. Each packet contains source and destination addresses, as well as error detection.

3. Network layer determines the route for transmitting information between networks, provides error handling, as well as data flow management. The main task of the network layer is data routing (data transfer between networks).

4. Transport layer connects lower levels (physical, channel, network) with upper levels, which are implemented by software. This level separates the means of generating data on the network from the means of transmitting it. Here the information is divided according to a certain length and the destination address is specified.

5. Session layer manages communication sessions between two interacting users, determines the beginning and end of a communication session, time, duration and mode of a communication session, synchronization points for intermediate control and recovery during data transfer; Restores the connection after errors during a communication session without losing data.

6. Executive- controls the presentation of data in the form required for the user program, performs data compression and decompression. The task of this level is to convert data when transmitting information into a format that is used in the information system. When receiving data, this data representation layer performs the inverse transformation.

7. Applied The level interacts with application network programs that serve files, and also performs computational, information retrieval work, logical transformations of information, transmission of mail messages, etc. The main task of this level is to provide a convenient interface for the user.

At different levels, different units of information are exchanged: bits, frames, packets, session messages, user messages.

1.4. network hardware

The main components of the network are workstations, servers, transmission media (cables) And network hardware.

Workstations are called network computers on which network users implement applied tasks.

Network servers- these are hardware and software systems that perform the functions of managing the distribution of public network resources. A server can be any computer connected to the network that contains resources used by other devices on the local network. Quite powerful computers are used as server hardware.

Networks can be created with any type of cable.

1. Twisted pair (TP- Twisted Pair) is a cable made in the form of a twisted pair of wires. It can be shielded or unshielded. Shielded cable is more resistant to electromagnetic interference. Twisted pair cable is best suited for small institutions. The disadvantages of this cable are the high signal attenuation coefficient and high sensitivity to electromagnetic interference, so the maximum distance between active devices on a LAN when using twisted pair cables should be no more than 100 meters.

2. Coaxial cable consists of one solid or twisted central conductor, which is surrounded by a layer of dielectric. A conductive layer of aluminum foil, metal braid, or a combination thereof surrounds the dielectric and simultaneously serves as a shield against interference. The overall insulating layer forms the outer sheath of the cable.

Coaxial cable can be used in two different data transmission systems: without signal modulation and with modulation. In the first case, the digital signal is used in the form in which it arrives from the PC and is immediately transmitted via cable to the receiving station. It has one transmission channel with a speed of up to 10 Mbit/s and a maximum range of 4000 m. In the second case, the digital signal is converted into analog and sent to the receiving station, where it is again converted into digital. The signal conversion operation is performed by the modem; Each station must have its own modem. This transmission method is multi-channel (provides transmission over dozens of channels using just one cable). In this way, sounds, video signals and other data can be transmitted. The cable length can reach up to 50 km.

3. Fiber optic cable is a newer technology used in networks. The information carrier is a light beam that is modulated by the network and takes the form of a signal. Such a system is resistant to external electrical interference and thus very fast, secure and error-free data transmission is possible at speeds of up to 2 Gbit/s. The number of channels in such cables is huge. Data transfer is carried out only in simplex mode, therefore, to organize data exchange, devices must be connected by two optical fibers (in practice, a fiber optic cable always has an even, paired number of fibers). The disadvantages of fiber optic cable include high cost and complexity of connection.

4. Radio waves in the microwave range are used as a transmission medium in wireless local networks, or between bridges or gateways for communication between local networks. In the first case, the maximum distance between stations is 200 - 300 m, in the second - this is the line-of-sight distance. Data transfer speed - up to 2 Mbit/s.

Wireless local networks are considered a promising direction for the development of LANs. Their advantage is simplicity and mobility. Problems associated with laying and installing cable connections also disappear - just install interface cards on workstations, and the network is ready to work.

The following types of network equipment are distinguished.

1. Network cards– these are controllers that are connected to expansion slots on the computer motherboard, designed to transmit signals to the network and receive signals from the network.

2. Terminators- These are 50 Ohm resistors that produce signal attenuation at the ends of the network segment.

3. Hubs (Hub) are the central devices of a cable system or a star physical topology network, which, when receiving a packet on one of its ports, forwards it to all the others. The result is a network with a logical common bus structure. There are active and passive concentrators. Active concentrators amplify received signals and transmit them. Passive hubs pass the signal through themselves without amplifying or restoring it.

4. Repeaters (Repeater) - network devices, amplifies and re-forms the shape of the incoming analog network signal at a distance of another segment. A repeater operates at an electrical level to connect two segments. Repeaters do not recognize network addresses and therefore cannot be used to reduce traffic.

5. Switches (Switch) - software-controlled central devices of the cable system that reduce network traffic due to the fact that the incoming packet is analyzed to determine the address of its recipient and, accordingly, is transmitted only to him.

Using switches is a more expensive but also more productive solution. A switch is usually a much more complex device and can serve multiple requests simultaneously. If for some reason the required port is busy at a given time, the packet is placed in the buffer memory of the switch, where it waits for its turn. Networks built using switches can cover several hundred machines and have a length of several kilometers.

6. Routers (Router) - standard network devices that operate at the network level and allow you to forward and route packets from one network to another, as well as filter broadcast messages.

7. Bridges (Bridge) - a network device that connects two separate segments, limited by their physical length, and transmits traffic between them. Bridges also amplify and convert signals for other types of cable. This allows you to expand the maximum network size while still maintaining restrictions on the maximum cable length, number of connected devices, or number of repeaters per network segment.

8. Gateways (Gateway) - hardware and software systems connecting heterogeneous networks or network devices. Gateways allow you to solve problems of differences in protocols or addressing systems. They operate at the session, presentation and application layers of the OSI model.

9. Multiplexers- These are central office devices that support several hundred digital subscriber lines. Multiplexers send and receive subscriber data over telephone lines, concentrating all traffic into one high-speed channel for transmission to the Internet or company network.

10. Firewalls (firewalls)- these are network devices that implement control over information entering and exiting the local network and providing protection to the local network by filtering information. Most firewalls are built on classical access control models, according to which a subject (user, program, process or network packet) is allowed or denied access to any object (file or network node) upon presentation of some unique element inherent only to this subject. In most cases, this element is a password. In other cases, such a unique element is microprocessor cards, biometric characteristics of the user, etc. For a network packet, such an element is addresses or flags located in the packet header, as well as some other parameters. Thus, a firewall is a software and/or hardware barrier between two networks that allows only authorized internet connections to be established. Typically, firewalls protect a corporate network connected to the Internet from outside penetration and prevent access to confidential information.

At Expocentre you can visit a huge number of exhibitions. Including exhibition "Communication", which will talk about a wide variety of telecommunications technologies and networks. In addition, it will be possible to find active and passive network equipment, figure out what the difference is between them and why it is necessary.

In the end, this is useful for each of us, because we live among it and actively use all the technologies, but we only have a rough idea of ​​how everything works.

What is network equipment?

This equipment includes everything that is used to transmit various signals between devices or to release them into the network.

All equipment is divided into huge groups, each of which has its own specific purpose and consistently fulfills it. Details and certain models may be improved every year, but the principle remains unchanged for a long time.

Now this list of groups looks something like this:

• Switching systems. Namely, all the moments and details that are responsible for connecting two subscribers.


• Satellite communication systems, channels via satellite, which provide high-quality communications around the world.


• Subscriber telecommunications equipment, i.e. personal equipment of each user, line assigned to him.


• Data transmission equipment.

All this is used simultaneously by every modern person, and sometimes even in several different forms at once. We cannot imagine our life without such features; we want to be able to easily communicate, receive information and transmit it ourselves.

Variety of network equipment

The entire variety of active and passive network equipment is reduced to three different options.

First of all, these are landline phones, which are almost a thing of the past, but nevertheless telephony continues to exist and is very actively used by some.

The second point is mobile communications. Even children now have such small phones, and active and passive network equipment allows everyone to instantly connect with their interlocutor.

The Internet is also actively used now, which is the most popular network at the moment for communication and obtaining information.

There is a huge amount of equipment itself, depending on the specific equipment. However, all of it is divided into active and passive network equipment, and these two groups differ from each other.

Active equipment

Among the huge amount of equipment, active equipment includes switches, hubs, adapters, routers, print servers and much more. Passive consists of sockets, various cables, connectors and similar items.

It is worth noting that it is the active that ensures the transfer of data, be it communication or simply watching the news, regardless of the channel and technology that is used for this, a computer or a telephone.

Active network equipment is responsible for ensuring that all information is sorted into packets, and that all packets are strictly separated along the necessary channels. Due to the enormous load, such technologies must be able to independently create a channel if necessary.

By the way, in order to protect the user’s equipment from breakdowns, these same various devices provide load distribution when receiving and sending packets.

Passive network equipment consists of a route and a path, namely cables and sockets, respectively. Both equipment provide connections, but in different ways, but one type simply could not exist without the other.

Modern active and passive network equipment is demonstrated at the annual SVIAZ exhibition.

Depending on the location and purpose of creating a local network, a variety of network equipment may be needed. At the same time, the modern market for equipment for local area networks amazes novice administrators with the variety of prices and models, so here we will look at what is required to combine computers within one knowledge.

Typical composition of local network equipment

Network cables

There are several types of network cables for installing a local network:

1. 1. Twisted pair is the most common (at the moment) type of cable used to connect computers into a local network. The cable consists of eight copper wires, which are connected in strict sequence via an RJ-45 connector.

There are many varieties of this cable, depending on the brand and conductivity. Cat 6 cable is very popular, which in addition to good cable protection also has high conductivity. The main disadvantage of creating a local network using twisted pair is the relatively short distance between connection points (it should not exceed more than one hundred meters).

1. 2. Fiber optic cable.

The main advantage of this cable is its good data transfer speed. There are no distance restrictions for such a connection, but the cost of optical fiber is significantly higher than “classic” twisted pair.

In addition, this cable requires special soldering at the connection points, which can only be done by a specialist with special equipment

Network cards

Typically, every computer is equipped with a network card. It is a device that allows you to send and receive data through network protocols.

There are two types of network cards:

1. 1. Built-in network card, looks like a board that is inserted into a special connector on a personal computer. It includes an RJ 45 connector and a data processor. Unlike desktop computers, laptops and netbooks are already equipped with a network card built into the motherboard.
2. 2. An external network card is mainly supplied in the form of a USB-RJ45 adapter. It is used on many personal computers and laptops that for some reason do not have the ability to install internal network cards.

Network switches

Special equipment that filters and amplifies the network signal. The main advantage of switches is traffic savings, since the switch sends a signal only to computers on the network, ignoring switched off equipment.

Switches are divided into several types depending on the following characteristics:

1. 1. Switch data transfer speed – i.e. at what speed network packets will be sent: 10, 100 or 1000 MB per second.
2. 2. The number of ports on the switch. Depending on the number of connected workstations in your local network, you can use a switch with 8, 16 or 24 ports.

Routers (routers)

This equipment is mainly used to connect networks (such as Ethernet and Wan). It also filters data transfer routes using a built-in algorithm.

LAN equipment can be active or passive. Passive elements include cable, box, switching devices such as cabinets, patch-panel, sockets, patch cords.

Active LAN equipment includes network adapters that perform the function of connecting the user to the LAN, supporting data exchange between the PC and the LAN data transmission medium. In addition, the network adapter acts as a temporary data storage and buffering.

Network cards can be divided into two types: adapters for client computers and adapters for servers. Depending on the Ethernet, Fast Ethernet or Gigabit Ethernet technology used, network cards provide data transfer rates of 10, 100 or 1000 Mbit/s.

Repeater(REPITER) is a repeater device designed to increase the length of a network segment.

Hub(ACTIVE HUBE) is a multiple access device with 4 to 32 ports, used to connect users to a network.

Bridge(BRIDGE) is a device (for example, a computer), with 2 ports, usually used to connect several LAN workgroups, allows you to filter network traffic by parsing network (MAC) addresses.

Switch(SWITCH) - a device with 4-32 ports that divides the overall data transmission medium into logical segments. Each logical segment is connected to a separate switch port to combine multiple LAN workgroups.

Router(ROUTER) - provides a choice of route (for example, a computer) for transferring data between several networks, as well as for combining several LAN workgroups, allows you to filter network traffic by parsing network (IP) addresses.

Media converter- a device, usually with two ports, usually used to convert data transmission media (coaxial-twisted pair, twisted pair-fiber)

Transceiver- signal amplifier, used for bidirectional transmission between the adapter and a network cable or two cable segments. Transceivers are also used as converters for converting electrical signals into other types of signals (optical or radio signals) in order to use other information transmission media.

Gateways- this is communication equipment (for example, a computer) that serves to combine heterogeneous networks with different exchange protocols. Gateways completely transform the entire data flow, including codes, formats, control methods, etc.

Active equipment - bridges, routers and gateways in a local area network use specialized software.

Who installs active equipment?

Installation of active equipment and its configuration are actually different from each other and must be carried out by highly specialized professionals according to a pre-developed project. Only in this case will you be able to do without wasted equipment that is not working correctly. For example, by contacting Russian Engineering Society You will always receive qualified advice, assistance in installing and configuring active equipment and will not be left alone with non-working equipment.

How not to get confused in the growing web of wires?

In the process of development of any enterprise, there is a constant process of changing the number of employees, increasing or reducing divisions, developing branches and remote departments. An enterprise, like a living organism, requires a “circulatory system” free of toxins; as it develops and expands, it involves an increasing number of employees, and the number of various active and executive equipment is growing. There comes a time when the company’s management decides to make further investments in the field of IT infrastructure and should get an excellent predictable result in building a modern network.

Implementation of the "new LAN" project

One of the areas of our activity is carrying out a full range of works on design, modernization, as well as supply and installation of active and passive equipment for creating IT infrastructure in small and medium-sized enterprises, building Data Processing Centers (DPCs), creating data storage systems, “ server rooms” equipped with low-current cable systems, uninterruptible power supply systems, monitoring systems and maintaining specified climatic conditions. We also equip these and any other premises with reliable security systems, such as video surveillance, fire alarms, access control and management.

We use ready-made, inexpensive solutions for integration with IT systems. All this allows you to optimize costs and expand the capabilities of existing equipment.

We use proven technologies, equipment and materials from certified manufacturers. We keep construction work on LAN installation to a minimum, focused on the end result, letters of gratitude and recommendations from Customers are the main indicator of our qualifications.

Advantages for the Customer when working with us