Connecting computers into a local network

The local network - the combination of several computers located at a short distance from each other (usually within the same building) to jointly solve information, computing, educational and other problems. A small local network may have 10-20 computers, a very large one - about 1000.

Purpose of local networks
· sharing common hardware (printer drives, modems)

· operational data exchange

· information system of the enterprise (institution)

Organization of local networks.

Although there are many different ways to connect computers together, there are essentially two types of computer networks: peer-to-peer networks and client-server networks.
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 a server, is the heart of the network. It stores information and resources and makes them available to other computers on the same network. The remaining computers using the network to obtain this information are called clients.

Client-server networks are the best option for connecting more than ten computers into a network. They are more expensive, but in cases where it is necessary to store a large amount of information, this is the best choice.

Models of various network configurations

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Local network topologies

Local networks, depending on their purpose and technical specifications, can have different configurations. The general scheme of connecting computers on a local network is called 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, there is a special central device (hub), from which “rays” 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 faults. If the cable is damaged in even one place, then problems arise for the entire network. The location of the fault is difficult to locate.
IN radial topology (star topology), in the center there is a hub 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 specific 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 capable of contacting any subscriber in the network.

In a network with a “ring” type structure, information is transmitted between stations along the ring with re-reception in each network controller. Reception is carried out through buffer drives made on the basis of random access memory devices, so if one network controller fails, 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 one network. For example, you can connect several star bus networks with a single cable.
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Local network equipment

How do computers communicate with each other?

The operation of the network is based on the fact that all pieces of equipment are connected to each other in one way or another. Each computer and equipment such as printers, scanners, laptops are connected using different cable sizes, satellite communications or telephone lines. Today there are even wireless networks that connect computers using radio waves.
Local network equipment generally includes:
· computers (servers and workstations);
· network cards (adapters);
· channels of connection;
· special devices that support the functioning of the network (routers, hubs, switches).
Each computer is connected to the network using a network card - adapter.
The network card is connected to the network card 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 cable for a network depends on the following indicators: installation and maintenance costs, data transmission speed, limitation on the distance of information transmission without additional repeater amplifiers (repeaters), data transmission security.
twisted pair 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 cable allows maximum transmission speeds of up to 10 Mbit/s. The cable length should not exceed 1000 meters, and the data transfer speed will not exceed 1 Mbit/s. To increase noise immunity, shielded twisted pair is used. Each twisted pair connects only one computer to the network, so a connection failure affects only this computer, which allows you to quickly find and fix problems.
Fiber Optic The cables transmit data in the form of light pulses along glass wires. Fiber optic cables provide the highest transmission speeds; they are more reliable because 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 speed over an optical cable is hundreds of thousands of megabits per second, which is about a thousand times faster than through twisted pair wires.

A fiber optic line is the most expensive type of connection today, but the speed of information dissemination in it reaches several gigabits per second with a permissible 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 do you plug the cable into your computer? You need an intermediate (interface) device, which is called a network card or network adapter, and in English NIC– Network Interface Controller.
Network adapter, or NIC, is a built-in 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 communications using 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 of up to 25 km (subject to line of sight).
In addition to cables and network adapters, twisted pair local networks use other network devices - hubs, switches and routers.
Hub(also called a hub) is a device that unites several (from 5 to 48) branches of a star-shaped local network and transmits information packets to all branches of the network equally.

Switch(switch) does the same thing, but, unlike a hub, it ensures the transmission of packets to specified branches. This ensures optimization of data flows on the network and increased security against unauthorized entry.

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

Gateway: an 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 accessible from workstations.
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Organization of data transmission on the network
A necessary condition for the operation of a unified local network is the use network operating system. Such operating systems provide sharing not only of network hardware resources (printers, drives, etc.), but also of distributed collective technologies when performing a variety of work. The most widely used network operating systems Novell NetWare,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 to ensure that the communication process occurs without errors. Protocols help define how information is sent and how it is received.

A local area network unites subscribers located at a short distance from each other (within 10-15 km). Typically, such networks are built within the same enterprise or organization.

Information systems built on the basis of local computer networks provide solutions to the following tasks:

• data storage;
• data processing;
• organizing user access to data;
• transfer of data and the results of their processing to users.

Computer networks implement distributed data processing. Here, data processing is distributed between two entities: the client and the server. During data processing, the client generates a request to the server to perform complex procedures. The server fulfills the request, provides storage of public data, organizes access to this data, and transmits the data to the client. This model of a computer network is called client-server architecture.

Based on the distribution of functions, local computer networks are divided into peer-to-peer and two-rank (hierarchical networks or networks with a dedicated server).

In a peer-to-peer network, computers have equal rights in relation to each other. Each user on the network decides for himself which resources of his computer he will provide for public use. Thus, the computer acts both as a client and as a server. Peer-to-peer sharing of resources is quite acceptable for small offices with 5-10 users, combining them into a work group.

A two-rank network is organized on the basis of a server on which network users register.

For modern computer networks, a mixed network is typical, combining workstations and servers, with some of the workstations forming peer-to-peer networks, and the other part belonging to two-peer networks.

The geometric connection diagram (physical connection configuration) of network nodes is called network topology. There are a large number of network topology options, the basic ones being bus, ring, and star.

Tire. The communication channel connecting 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 who the information is addressed to, and accepts the data if it is sent to it, or ignores it.

With a bus topology, the information transmission medium is represented in the form of a communication path accessible to all workstations, to which they all must be connected. All workstations can communicate directly with any workstation on the network. If computers are located close to each other, then organizing a computer network 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

Workstations can be connected to or disconnected from it at any time, without interrupting the operation of the entire computer network. The functioning of a computer network does not depend on the state of an individual workstation.

In a standard situation, an Ethernet bus network often uses a thin cable or a Cheapernet cable with a T-connector. Shutting down and especially connecting to such a network requires a bus break, which disrupts the circulating flow of information and causes the system to freeze.

Bus topology problems arise when a break occurs (contact failure) anywhere in the country; the network adapter of one of the computers fails and begins to transmit signals with noise to the bus; you need to connect a new computer.

Ring. The nodes are connected into a closed curve network. The workstation sends information to a specific destination address, having previously received a request from the ring. Data transfer is carried out in one direction only. Each node, among other things, implements the functions of a repeater. He receives and transmits messages, and perceives only those addressed to him. Using a 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. Message forwarding is very efficient since most messages can be sent “on the road” over the cable system one after another. It is very easy to make a ring request to all stations. The duration of information transfer increases in proportion to the number of workstations included in the computer network.

With a ring network topology, workstations are connected to one another in a circle, i.e. workstation 1 with workstation 2, workstation 3 with workstation 4, etc. The last workstation is connected to the first. The communication link is closed in a ring.

Laying cables from one workstation to another can be quite complex and expensive, especially if the workstations are geographically located far from the ring (for example, in a line).

The main problem with a ring topology is that each workstation must actively participate in the transfer of information, and if at least one of them fails, the entire network is paralyzed. Faults in cable connections are easily localized.

Connecting a new workstation requires a short-term shutdown of the network, since the ring must be open during installation. There is no limit on the length of a computer network, since it is ultimately determined solely by the distance between two workstations.

Ring topology

A special form of ring topology is a logical ring network. Physically, it is mounted as a connection of star topologies. Individual stars are switched on using special switches (English Hub - concentrator), which in Russian are also sometimes called “hub”. Depending on the number of workstations and the length of the cable between workstations, active or passive hubs are used. Active hubs additionally contain an amplifier for connecting from 4 to 16 workstations. The passive hub is purely a splitter device (for a maximum of three workstations). Managing an individual workstation in a logical ring network is the same as in a regular ring network. Each workstation is assigned an address corresponding to it, through which control is transferred (from senior to junior and from junior to senior). The connection is broken only for the downstream (closest) node of the computer network, so that only in rare cases can the operation of the entire network be disrupted.

Logic ring structure

Disadvantages of a ring organization: a break at any point in the ring stops the operation of the entire network; the time of message transmission is determined by the time of sequential operation of each node located between the sender and recipient of the message; Due to the flow of data through each node, there is a possibility of unintentional distortion of information.

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

The concept of a star network topology comes from the field of mainframe computers, in which the head machine receives and processes all data from peripheral devices as the active processing node. This principle is used in data communication systems, such as RELCOM e-mail. All information between two peripheral workstations passes through the central node of the computer network.

Network throughput is determined by the computing power of the node and is guaranteed for each workstation. There are no data collisions.

Star topology

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 (merging) computer networks. The fact is that a computer network created at a certain stage of development of an information system may, over time, 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 strict restrictions on the number of nodes and the geometric dimensions of the network.

The following devices are used to connect local area networks:

1. A repeater is a device that provides amplification and filtering of a signal without changing its information content. As the signals travel along communication lines, they fade. Repeaters are used to reduce the effect of attenuation. Moreover, the repeater not only copies or repeats received signals, but also restores the characteristics of the signal: it amplifies the signal and reduces interference.

2. A bridge is a device that performs the functions of a repeater for those signals (messages) whose addresses satisfy pre-imposed restrictions. One of the problems of large networks is heavy network traffic (the flow of messages on the network). This problem can be solved as follows. A computer network is divided into segments. The transmission of messages from segment to segment is carried out only purposefully if a subscriber of one segment transmits a message to a subscriber of another segment. A bridge is a device that restricts movement across a network and prevents messages from passing from one network to another without confirming the right to cross.

Bridges can be local or remote.

Local bridges connect networks located in a limited area within an existing system.

Remote bridges connect geographically dispersed networks using communication channels and modems.

Local bridges, in turn, are divided into internal and external.

Internal bridges are usually located on one computer and combine the function of a bridge with the function of a subscriber computer. Expansion of functions is carried out by installing an additional network card.

External bridges require the use of a separate computer with special software.

3. A router is a device that connects different types of networks but uses the same operating system. This is, in fact, the same bridge, but with its own network address. Using the addressing capabilities of routers, hosts on a network can send messages to a router that are intended for another network. Routing tables are used to find the best route to any destination on the network. These tables can be static or dynamic.

4. A gateway is a special hardware and software complex designed to ensure compatibility between networks using different communication protocols. The gateway converts the presentation form and data formats when transmitting them from one segment to another. The gateway performs its functions at a level above the network level. It does not depend on the transmission medium used, but depends on the data exchange protocols used. Typically a gateway performs conversions between protocols.

Using gateways, you can connect a local area network to a host computer, as well as to a global area network.

Let's take a closer look at the principles of constructing local area networks (LANs).

New technologies offer passive plug boxes through which workstations can be turned off and/or turned on while the computer network is running.

Due to the fact that workstations can be turned on without interrupting network processes and the communication environment, it is very easy to eavesdrop on information, i.e. branch information from the communication environment.

In a LAN with direct (non-modulated) information transmission, there can always be only one station transmitting information. To prevent collisions, in most cases, a time division method is used, according to which each connected workstation is granted an exclusive right to use the data transmission channel at certain points in time. Therefore, the requirements for computer network bandwidth under increased load are reduced, for example, when new workstations are introduced. Workstations are connected to the bus using TAP devices (Terminal Access Point). TAP is a special type of connection to coaxial cable. The needle-shaped probe is inserted through the outer shell of the outer conductor and the dielectric layer to the inner conductor and is connected to it.

In a LAN with modulated broadband information transmission, various workstations receive, as needed, a frequency on which these workstations can send and receive information. The transmitted data is modulated at the corresponding carrier frequencies, i.e. Between the information transmission medium and the workstations there are modems for modulation and demodulation, respectively. The technology of broadband messages makes it possible to simultaneously transport a fairly large amount of information in a communication environment. For the further development of discrete data transportation, it does not matter what initial information is supplied to the modem (analog or digital), since it will still be converted in the future.

Characteristics of computer network topologies are given in the table.

Characteristics	Topology
Expansion cost	Minor
Connecting subscribers	Passive	Active	Passive
Failure Protection	Minor	Minor
System Dimensions			Limited
Security against eavesdropping			Minor
Connection cost	Minor	Minor
System behavior under high loads		Satisfactory
Ability to work in real time	Very good
Cable routing		Satisfactory
Service	Very good

Along with the well-known topologies of computer networks: ring, star and bus, a combined structure, for example a tree structure, is also used in practice. It is formed mainly in the form of combinations of the above-mentioned computer network topologies. The base of the computer network tree is located at the point (root) at which communication lines of information (tree branches) are collected.

Tree structure of LAN

Computer networks with a tree structure are used where direct application of basic network structures in their pure form is not possible. To connect a large number of workstations, network amplifiers and/or switches are used according to adapter boards. A switch that simultaneously has amplifier functions is called an active hub.

In practice, two varieties are used, providing the connection of eight or sixteen lines, respectively.

A device to which a maximum of three stations can be connected is called a passive hub. A passive hub is usually used as a splitter. It doesn't need an amplifier. The prerequisite for connecting a passive hub is that the maximum possible distance to the workstation should not exceed several tens of meters.

Moscow State Mining University

Department of Automated Control Systems

Course project

in the discipline "Computer networks and telecommunications"

on the topic: “Design of a local area network”

Completed:

Art. gr. AS-1-06

Yuryeva Ya.G.

Checked:

Prof., Doctor of Technical Sciences Shek V.M.

Moscow 2009

Introduction

1 Design task

2 Description of the local area network

3 Network topology

4 Local network diagram

5 OSI reference model

6 Justification for choosing a local network deployment technology

7 Network protocols

8 Hardware and software

9 Calculation of network characteristics

Bibliography

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

The main advantages provided by a local network are the ability to collaborate and quickly exchange data, centralized data storage, shared access to shared resources such as printers, the Internet and others.

Another important function of a local network is the creation of fault-tolerant systems that continue to function (albeit not fully) if some of their elements fail. In a LAN, fault tolerance is ensured through redundancy and duplication; as well as flexibility in the operation of individual parts (computers) included in the network.

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

Building a reliable LAN that meets your performance requirements and has the lowest cost requires starting with a plan. In the plan, the network is divided into segments, and a suitable topology and hardware are selected.

The bus topology is often called a linear bus. This topology is one of the simplest and most widespread topologies. It uses a single cable, called a backbone or segment, along which all computers on the network are connected.

In a network with a “bus” topology (Fig. 1.), computers address data to a specific computer, transmitting it over a cable in the form of electrical signals.

Fig.1. Bus topology

Data in the form of electrical signals is transmitted to all computers on the network; however, only the one whose address matches the recipient address encrypted in these signals receives information. Moreover, at any given time, only one computer can transmit.

Since data is transmitted to the network by only one computer, its performance depends on the number of computers connected to the bus. The more there are, i.e. The more computers waiting to transfer data, the slower the network.

However, it is impossible to derive a direct relationship between network bandwidth and the number of computers in it. Since, in addition to the number of computers, network performance is influenced by many factors, including:

· hardware characteristics of computers on the network;

· the frequency with which computers transmit data;

· type of running network applications;

· type of network cable;

· distance between computers on the network.

The bus is a passive topology. This means that computers only “listen” to data transmitted over the network, but do not move it from sender to recipient. Therefore, if one of the computers fails, it will not affect the operation of the others. In active topologies, computers regenerate signals and transmit them across the network.

Signal reflection

Data, or electrical signals, travel throughout the network - from one end of the cable to the other. If no special action is taken, the signal reaching the end of the cable will be reflected and will not allow other computers to transmit. Therefore, after the data reaches the destination, the electrical signals must be extinguished.

Terminator

To prevent electrical signals from being reflected, terminators are installed at each end of the cable to absorb these signals. All ends of the network cable must be connected to something, such as a computer or a barrel connector - to increase the cable length. A terminator must be connected to any free - unconnected - end of the cable to prevent electrical signals from being reflected.

Local network in the office

An example of a local network in an office in schematic form

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

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

Organization of the company's telephone network using the Internet. Creation of a telephone network with high-quality telephone communications. Organizing free phone calls for clients.

Local network diagram

Features of the local network

An example of a local network is given for a more understandable and informative presentation of the network’s operation with prioritization of the transmission of various types of traffic: Internet, telephone traffic, television.

Local network diagram

In today's conditions of fierce competition, it is important to quickly respond to any changes. The stability of any company, cafe, store or large corporation directly depends on the reliability and well-thought-out typology of the local network.

Key advantages of local networks for business:

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

Instant exchange of reports between departments;

Organization of shared access to office equipment (printers, chamfers, copiers, scanners);

Organization of Internet access from all workstations;

Ability to automate routine processes;

Organization of free and secure corporate communications between individual offices and buildings.

A well-designed local area network significantly increases the efficiency of an enterprise, frees up human resources, and provides a lot of additional opportunities.

Why should you entrust the development of a corporate local network to Canmos?

In small offices where two or three computers need to be connected, a local network can be organized in-house. But in most enterprises it is better to trust a specialized company.

Without experience, practical skills and knowledge of the network equipment market, serious budget overruns are possible without achieving the desired result. Sometimes, an incorrect connection or saving on cables and connectors leads to the fact that expensive equipment only works at 10-20% of its capabilities. The result is constant delays, failures, burning ports, or even system failure.

Without developing a detailed plan after completing the work, it may turn out that you forgot to lay a line for the network printer, and all the ports in the router are occupied and there is no way to connect another device. Since scaling was not provided for in advance, when expanding the office, there was simply nowhere to “stick in new” computers.

With Canmos, all network problems will be a thing of the past. We have been providing communication services and designing data transmission systems for many years. When developing the network we:

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

We will provide scaling and convenient addition of new workstations with minimal investment;

We will provide protection from external and internal threats;

We guarantee ease of management.

Typical LAN diagram from Canmos

When designing a LAN, preference is given to the “Star” typology - each node (computers, network printers) is connected to the switch with a separate cable. This solution provides:

Independent operation of each workstation, which increases network reliability;

Minimum cost and ease of adding new devices to the network as the enterprise expands.

To increase reliability and fault tolerance, simplify administration, and optimize loads between network equipment, the local computer network is divided into several segments - subnets are connected to each other by a high-speed optical channel. Mail, file and 1C servers, and PBX operate in a separate segment.

To simplify administration, computers in different departments, such as accounting, commercial or legal, are combined into working groups.

Wireless network access is provided by wi-fi access points.

Technically, when laying LAN networks, it is optimal to place server and network equipment in a separate room to provide quick access from one place for the network administrator. Sockets for RJ-45 and RJ-12 (for IP telephony) are installed near employee workstations.

In the future, depending on the needs of the enterprise, office IP telephony can be deployed on the basis of a ready-made local network (for a stable connection, priority is provided with a speed of 64 kb/s per device), and a 1C network. A secure (encrypted) connection to the local network of remote employees via a VPN channel can be provided.

Due to the large area of ​​the territory, the large number of buildings, workshops, departments and users (about 1500 users), in order to increase the performance and fault tolerance of the network, it is necessary to divide it into logically independent objects, which will be interconnected by node network devices. At the same time, dividing a large network into smaller ones will make it easier to administer. Thus, the enterprise LAN topology will be designed in the form of a hierarchical star. The link layer technology will be a family of high-speed versions of Ethernet.

To ensure separation of responsibilities between switches, a standard architecture will be used, consisting of: network core level switches, distribution level switches and access level switches. Switches installed at the network core level require high performance and fault tolerance. Since the performance of the entire network will depend on them. Distribution switches will be located throughout the enterprise, closer to groups of access switches, to which end users of LAN resources are already connected. Server cabinet switches are connected directly to the network core switch, which serve the so-called SAN (Storage area network), local networks inside the server cabinets.

The enterprise is divided into 5 zones, each of which will be served from its own distribution level switch. Zones are selected depending on location and number of users. The enterprise LAN diagram is shown in Figure 2.

Logically, such a large network should be divided into several smaller networks. With this approach, network performance will increase, since broadcast and other “junk traffic” will not spread across all networks, taking up network bandwidth. In the event of a network failure, such as a broadcast storm, only a small logical fragment of the network will fail, the problem in which can be identified and corrected much faster. That is, in this case, the convenience of network administration is ensured. When carrying out any work to rebuild the network, it will be possible to do this in parts, which simplifies the work of network administrators and allows a small number of users to be taken out of service while the work is being carried out.

Figure 2 - Enterprise LAN topology

Virtual local area network (VLAN) technology will be used to divide the network. Each division, and sometimes a group of smaller divisions, will have its own virtual network. Several vlans will also be created to connect the switches of the network core and the distribution layer. Each such network will use unique network addresses. Virtual networks will use switch ports at the core and distribution levels to place units in their own unique vlans. This will be done during the configuration of active network devices.

As can be seen from the diagram, several logical channels will be used to connect the core and distribution switches. The core topology of the “star + ring” network will be implemented. From the core switch, channels radiate in a star pattern to the distribution switches; they are highlighted in blue in the diagram. This creates a “star”. These channels will be allocated to a separate vlan, which will be used only for communication between backbone switches.

The channels that will connect the backbone switches into a “ring” are highlighted in yellow. Previously, it was not acceptable to create loops in Ethernet networks. But the requirements for network reliability led to the development of technologies capable of supporting redundant connections in the network for channel reservation. Ethernet Ring Protection Switching (ERPS) is one of the technologies that allows you to organize fault-tolerant network topologies. It was chosen over Rapid Spanning Tree Protocol (RSTP) due to the quick time it takes to restore the network in the event of a failure of one of the channels. For RSTP the convergence time is less than 10 seconds, while for ERPS it is less than 50 milliseconds. This will also be a separate vlan, used only by backbone switches.

Dynamic routing will be used to unite all virtual networks and find routes between them. Namely, the Open Shortest Path First version 2 (OSPFv2) protocol. Each of the backbone switches will be able to operate at layer 3 of the OSI model, that is, it will be an L3 switch. In the OSPF protocol domain, one backbone zone will be allocated - the backbone. It will contain only routers (built into L3 switches), which will exchange information with each other about the virtual networks connected to them. This protocol requires the allocation of the OSPF domain root - Designated root (DR), and the presence of a backup root - Backup designated root (BDR). A core-level switch will be used as a DR, and one of the distribution-level switches will be used as a BDR.

Each user access layer switch will be used in its own specific vlan allocated for it on the distribution layer switch. In some cases, such switches can be used to connect switches with fewer ports to them, but this does not matter for the logic of the network.

In this way, a productive, fault-tolerant and easily scalable local area network architecture is organized.