What is a public network? Unified telecommunication network: public communication network, dedicated communication networks. Departmental communication networks, dedicated communication networks of individuals and legal entities

There are the following types of public telephone networks (PSTN): urban, rural, zonal and long-distance.

The structure of the PSTN takes into account the administrative-territorial division of the country. In accordance with this, the PSTN unites local and intra-zonal telephone networks, as well as a long-distance telephone network.

Local telephone networks include networks created in cities and rural areas. Accordingly, local networks are divided into urban and rural telephone networks (GTS and STO).

All local telephone networks geographically located in a certain zone are combined into a zone network. The territory of the zones, as a rule, coincides with the territory of the regions, in some cases the territory or the republic.

The main criterion for the formation of zones is the number capacity of networks, i.e. the number of subscribers, which is determined by a single seven-digit numbering within one zone.

The largest cities in the country with seven-digit numbering of subscriber devices are allocated into independent zones.

The switching center of the zonal telephone network is an automatic long-distance telephone exchange (ATS), with which all automatic telephone exchanges (ATS) of urban telephone networks and central stations of rural telephone networks are connected directly or through special nodes.

Automatic MTS communicates between local networks of the zone; and provides exit beyond the zone. Each zone has, as a rule, one, and sometimes several automatic telephone exchanges. In the latter case, one of the ATEs located in the administrative center of the zone is the main one, and all ATEs of the zone are connected to each other according to the “each to each” principle.

All zonal telephone networks are united into a single nationwide network using an intercity automatically switched telephone network.

The long-distance telephone network consists of automatic switching nodes (ASK) and automatic telephone exchanges, interconnected by bundles of telephone transmission channels.

All telephone networks - local, zonal and long-distance - are built according to the radial-node principle. Figure 2 shows a simplified diagram of the PSTN construction. Elements of the long-distance telephone network in the diagram are highlighted with bold lines. End stations

intercity telephone network are automatic telephone exchanges. Automatic switching nodes perform only transit connections. There are automatic switching nodes of the first and second classes of UAC I and UAC II.

The long-distance telephone network has twelve UAC.I, connected by bundles of telephone channels according to the “each to each” principle. Each UAC I is a switching center serving a specific territorial area. All automatic telephone exchanges located in this territory communicate with UAK I directly or through automatic switching nodes of the second class (UAK II). Consequently, each UAKI has a connection with all other UAKI of the network, and in addition, with UAKII and some telephone exchanges located in its transit territory.

Automatic switching nodes of the second class are an intermediate link between UAC I and several automatic telephone exchanges of the territory and are created if there is a technical and economic feasibility of combining the load of groups of telephone exchanges. Some ATEs can be connected simultaneously with UAK II and UAK I, and if necessary (the presence of mutual attraction) can have direct channels with other ATEs (shown in Fig. 2 with dashed lines).

Each telephone exchange serves one zonal telephone network. In the figure, the dash-dot lines conventionally show the territories of the serviced zones. The telephone network of the dedicated zone consists of three local networks: two private telephone networks and one local telephone network connected to the telephone exchange.

Figure 2 – PSTN construction diagram.

In addition to the PSTN, there are also institutional, departmental, corporate telephone networks that provide internal telephone communications for enterprises, institutions, corporations, and organizations. Such networks can be completely autonomous, but most often they have access to the public telephone network.

In accordance with Part 1 of Article 12 of the Federal Law of July 7, 2003 No. 126-FZ “On Communications” (Law 126-FZ), the unified telecommunication network of the Russian Federation consists of telecommunication networks of the following categories located on the territory of the Russian Federation.

public communications network;
dedicated communication networks;
technological communication networks connected to the public communication network;
special purpose communication networks.

Public communications network

The public communications network is intended for the provision of paid telecommunications services to any user of communications services on the territory of the Russian Federation.

Based on this, we can conclude that the contract for the provision of communication services concluded by the public communications network operator is a public contract. According to Article 426 of the Civil Code (Civil Code), a public contract is an agreement concluded by a commercial organization and establishing its obligations for the sale of goods, performance of work or provision of services that such an organization, by the nature of its activities, must carry out in relation to everyone who turns to it (retail trade , transportation by public transport, communication services, energy supply, medical, hotel services, etc.). A commercial organization does not have the right to give preference to one person over another with regard to concluding a public contract, except in cases provided for by law and other legal acts. In addition, the price of communication services, as well as other terms of the public contract, are established the same for all consumers, with the exception of cases where the law and other legal acts allow the provision of benefits for certain categories of consumers.

A commercial organization's refusal to conclude a public contract if it is possible to provide the consumer with appropriate communication services is not allowed. If a commercial organization unreasonably evades concluding a public contract, the other party has the right to apply to the court with a demand to compel the conclusion of the contract. A party that unreasonably evades concluding a contract must compensate the other party for the losses caused by this.

The public communications network includes:

telecommunication networks defined geographically within the service territory and numbering resource. The code of a geographically defined numbering zone is a part of the characters in the digital structure of the number that determines the location of the user (terminal) equipment within the territory of a constituent entity of the Russian Federation;
telecommunication networks that are not geographically defined within the territory of the Russian Federation and the numbering resource. The code of a geographically non-defined numbering zone is a part of the characters in the digital structure of a number that determines the type of telecommunication service or telecommunication network operating within the entire territory of the Russian Federation or part of it.

The telephone communication network includes:

fixed telephone networks, defined geographically within the service territory and using the numbering resource of geographically defined numbering zones;
mobile radio networks that are not geographically defined within the territory of the Russian Federation and use the numbering resource of geographically non-defined numbering zones;
mobile radiotelephone networks that are not geographically defined within the territory of the Russian Federation and use the numbering resource of geographically non-defined numbering zones;
mobile satellite radio networks that are not geographically defined and use the numbering resource of geographically non-defined numbering zones.

Communication networks, defined by the technology for implementing communication services, include:

data networks;
telegraph communication networks (including Telex networks);
communication networks for the distribution of television and radio broadcasting programs;
communication networks, determined by the technology for implementing the provision of communication services.

A public communications network is a complex of interacting telecommunication networks, including communications networks for the distribution of television and radio broadcasting programs.

Interaction of communication networks is possible when they are connected to each other. Connection of telecommunication networks is the establishment of technical and technological interaction of communication means of two communication networks, in which it becomes possible to pass traffic between these networks, bypassing other communication networks. Connection of television and radio broadcasting communication networks is the establishment of technical and technological interaction of communication means of two television and radio broadcasting communication networks, in which it becomes possible to transmit signals from television programs and (or) radio programs between these networks, bypassing other communication networks. Connection of telecommunication networks and their interaction are carried out on the basis of concluded agreements. The public communications network has connections to the public communications networks of foreign countries.

The television and radio broadcasting communication network is part of the public communication network, determined by the technology for implementing communication services, and includes:

terrestrial television and radio broadcasting networks;
cable television and radio broadcasting networks;
satellite television and radio broadcasting networks;
wired radio broadcasting networks.

Dedicated communication networks

In accordance with Part 1 of Article 14 of Law 126-FZ, dedicated communication networks are telecommunication networks intended for the provision of paid telecommunication services to a limited circle of users or groups of such users. This network operates only within a specified circle of users, and this is its main difference from the public communications network.

Dedicated communication networks can interact with each other, i.e. they can have attachment points and exchange traffic. An important condition is that this interaction can only take place between dedicated networks. In addition, for dedicated communication networks operating on the territory of the Russian Federation, requirements for the identification of communication networks, their nodes and terminal elements, including the significance of the number, are established independently by the operators of these communication networks, taking into account the recommendations of the Ministry of Communications and Mass Media of the Russian Federation.

Dedicated communication networks do not have connections to the public communication network, as well as to the public communication networks of foreign countries. A dedicated communication network can be connected to a public communication network only in one case - when it is transferred to the category of a public communication network, if the dedicated communication network meets the requirements established for a public communication network. In this case, the allocated numbering resource is withdrawn and a numbering resource is provided from the numbering resource of the public communication network.

Technologies and means of communication used to organize dedicated communication networks, as well as the principles of their construction, are established by the owners or other owners of these networks. This is also another difference between a dedicated communication network and a public communication network. For the latter, general universal rules apply, approved by the competent government bodies.

Communication operators of all categories of communication networks of the unified telecommunications network of the Russian Federation are required to create management systems for their communication networks that comply with the established procedure for their interaction.

In accordance with Part 2 of Article 14 of Law 126-FZ, the provision of communication services by operators of dedicated communication networks is carried out on the basis of appropriate licenses within the territories specified therein and using the numbering assigned to each dedicated communication network in the manner established by the federal executive body in the region communications.

There are two types of names of communication services included in licenses for carrying out activities in the field of providing communication services:

telephone services in a dedicated communication network;
mobile radio services in a dedicated communication network.

4. Technical requirements for connection to public communication networks

4.1. Technical conditions for connection

4.1.1. Technical conditions for connecting a communication network to a public communication network are issued by the public network operator to the operator of the connected network upon written request. If the provision of services that the connected network intends to provide to users is subject to licensing in accordance with current legislation, a copy of the license issued by the Ministry of Communications of the Russian Federation is attached to the request.

Refusal to issue technical conditions for connection to a network operator that has the appropriate license is not allowed.

4.1.2. Technical conditions for connection must reflect:

the specific way in which connections between networks are established;

technical parameters at network connection points (signal levels, signal spectra, transmission speeds, signaling types, signal codes, cable types, etc.);

method of accounting for traffic from the connected communication network (outgoing and incoming);

interaction of control systems and technical operation, including the method of organizing interaction between control centers of the connected network and the public network;

interaction of synchronization systems;

a list of construction and installation works that must be performed to carry out the connection, including, if necessary, the expansion of switching capacity and interstation channel banks of the public network in all necessary areas for passing traffic from/to the connected network in accordance with the current VNTP and other regulatory and technical documentation , containing requirements for communication networks;

stage of connection work.

4.1.3. It is not allowed to include in the technical conditions for connection the construction of objects and structures and the installation of equipment that are not related to the transmission of traffic from/to the connected network other than on a compensatory basis.

4.2. Connection to the public telephone network

4.2.1. Joining at local level

4.2.1.1. The connected network, depending on the ratio of its capacity (at the end of the license period) and the capacity of the local public communication network, can be connected to the latter as an institutional PBX, district PBX, a hub area of a zoned urban local network, or a terminal or hub PBX of a rural local network.

Networks with a capacity of less than 1000 numbers are included in public city networks only as corporate PBXs or city PBX hubs.

In some cases, subject to mandatory approval by the Ministry of Communications of the Russian Federation, the connected network may contain a switching node through which connections between subscribers of the public communications network pass.

4.2.1.2. Communication networks providing telematics services are usually included in telephone networks at the level of subscriber installations. It is allowed to include networks providing telematic services and information and reference services as special services of local telephone networks. A specific decision on the method of connection is made by the operator of the public communications network, if the license of the operator of the connected network does not contain specific instructions on the method of connection.

4.2.1.3. The numbering allocated to the connected network (its switching stations and subscriber installations with access to the public communications network) is determined by the operator of the latter when issuing technical conditions for connection.

4.2.1.4. If technically possible, it is permitted to organize direct channel bundles between switching stations of the connected network and automatic telephone exchanges of the public network located in the same numbering zone, while maintaining the uniform numbering of subscribers of the connected network.

4.2.2. Connection at intrazone level

4.2.2.1. With this method of connection, the connected network is included in the automatic telephone exchange of the public communication network as a local network and is assigned an intra-zone access code ab. The code is selected in accordance with the current numbering plan for the public communications network.

4.2.2.2. The numbering allocated to the connected network is determined by the operator of the public communication network with mandatory agreement with the Giprosvyaz Institute (assigned to the given region) when issuing technical conditions for connection.

4.2.2.3. If technically possible, it is permitted to organize direct channel bundles between switching stations of the connected network and international telephone exchanges of the public network while maintaining the unity of numbering of subscribers of the connected network.

4.2.2.4. To connect at the intrazone level, the connected network, according to the license (for the last year of its validity), must have an installed capacity of at least the average capacity of the local network in the numbering zone in question, but in any case not less than 30,000 numbers.

If the network capacity is more than 60,000 numbers, it can be allocated more than one intrazone ab code.

4.2.3. Intercity connection

4.2.3.1. With this connection method, the connected network is included in the public long-distance communication network as a numbering zone and is assigned a long-distance access code ABC.

4.2.3.2. The intercity code allocated to the connected network is determined by the Ministry of Communications of the Russian Federation in accordance with the numbering plan for the public communications network of the Russian Federation.

4.2.3.3. Connection of a communication network to a public network at the intercity level is allowed only for existing networks that have an installed capacity of their own local switching stations of at least 300 thousand numbers with a utilization rate of at least 50%.

4.2.3.4. In certain technically justified cases, simultaneous connection of communication networks to the public network at the intercity and local levels is permitted. In this case, connection at the local level is carried out separately in each numbering zone of the public network where such connection is carried out, in accordance with these Regulations and the principles of constructing a public telephone network.

4.2.4. Connection at the level of subscriber installations is carried out in accordance with the current rules for the provision of services by local telephone networks of the Russian Federation.

4.3. Connection to public telegraph networks

4.3.1. As public telegraph networks, these Regulations consider the public telegraph network with message switching and subscriber telegraph networks - the AT-50 network (national) and the Telex network (international), in the future - the unified AT/Telex network.

4.3.2. Connection to public subscriber telegraphy networks (AT-50, Telex) is permitted for departmental and other subscriber telegraphy networks, data transmission networks and telematic services.

4.3.3. Connection to the public telegraph network with message switching (TG-OP) is allowed for telegraph networks whose operators are licensed to provide the Telegram service or provide the specified service under an agreement with the operators of the TG-OP network.

The procedure for connecting other networks and equipment to the TG-OP network for transmitting non-telegraph traffic is determined by a separate regulation approved by the Ministry of Communications of the Russian Federation.

4.3.4. Connection to public telegraph networks is carried out, as a rule, at the level of subscriber installations (AT-50, Telex) or end points (TG-OP). In this case, specific connection points and numbering of the corresponding telegraph network allocated to the connected network or service are established by regional (zonal) operators of public telegraph networks.

4.3.5. In some cases, if the connected network has the appropriate technical means, connection to public telegraph networks is allowed at the level of channel switching stations (substations) (AT-50, Telex) or message switching centers (hubs) (TG-OP). In this case, specific connection points and numbering of the corresponding telegraph network allocated to the connected network or service are established by the Ministry of Communications of the Russian Federation.

4.3.6. Transit transmission of public telegraph network traffic through connected networks is not permitted, with the exception of public data networks designated by the Ministry of Communications of the Russian Federation as transport networks for the transmission of telegraph traffic.

4.4. Connection of personal radio call networks to the public telephone network

The connection of personal radio call networks to the public telephone network is carried out in accordance with the concept adopted by the State Committee for Electric Networks of Russia.

4.5. Connection of mobile radio networks to the public telephone network

The connection of mobile radio communication networks to the public telephone network is carried out in accordance with the concept adopted by the State Committee for Electric Networks of Russia.

4.6. Connection of trunking networks to the public telephone network

The connection of trunking networks to the public telephone network is carried out in accordance with the concept adopted by the State GKES of Russia.

Question No. 1. Basic concepts and definitions of telecommunication systems.

Federal Communications of the Russian Federation is a collection of various bodies, organizations and entities providing electrical and postal communications on the territory of the Russian Federation. It is designed to meet the needs of the population, public authorities and administration, defense, security, law and order, as well as business entities for electrical and postal communication services.

The material and technical basis of federal communications is the Unified Telecommunication Network (UTN) of the Russian Federation and the postal network of the Russian Federation (Fig. 1).

(slide 5)

Rice. 1. Material and technical basis of federal communications of the Russian Federation.

(slide 6)

Telecommunication is any transmission or reception of signs, signals, voice information, written text, images, sounds via wire, radio, optical and other electromagnetic media or systems.

Communication system is an organizational and technical association of forces and communications facilities created in the Armed Forces as a whole, as well as in an association, formation (military unit) for the exchange of all types of information in the system of command and control of troops (forces) in an operation (battle) and in their daily activities .

It can be stationary or field (mobile).

The communication system of a formation (military unit) usually includes:

Communication nodes of control points (CS PU);

Lines of direct communication between control systems;

Snap communication lines;

Courier-postal communication network;

Communication management system;

Technical support system for communications and automated control systems (TOS and ACS);

Reserve forces and means of communication.

(slide 7)

A communication network is a part of a communication system, distinguished by functional characteristics (type or type of communication).

Telecommunication networks are the basis (transport medium) of electrical information systems.

The Unified Telecommunication Network of the Russian Federation is a complex of technologically interconnected telecommunication networks of various categories on the territory of the Russian Federation.

The components of the Unified Energy System of the Russian Federation are:

Public communication network;

Dedicated communication networks;

Technological communication networks;

Special purpose communication networks.

(slide 8)

Public Communications Network (GSN) is intended for the provision of paid telecommunication services to any user of communication services on the territory of the Russian Federation. A public communication network is a complex of interacting telecommunication networks, including communication networks for broadcasting television channels and (or) radio channels. The public communications network has connections to the public communications networks of foreign countries.

(slide 9)

Dedicated communication networks– telecommunication networks intended for the provision of paid telecommunication services to a limited number of users or groups of such users. Dedicated communication networks can interact with each other. Dedicated communication networks do not have connections to the public communication network, as well as to the public communication networks of foreign countries. Technologies and means of communication used to organize dedicated communication networks, as well as the principles of their construction, are established by the owners or other owners of these networks.

(slide 10)

Technological communication networks are intended to support the internal production activities of organizations and manage the production process. Technological communication networks cannot be used to provide paid telecommunication services. If there are free resources, parts of technological communication networks can be connected to the SSOP and transferred to the SSOP category. These parts must be able to be technically separated from the organization's overall technological communication network. In the case of using a technological communication network to provide paid services to a limited group of users without joining the SSTN, this network goes into the category of a dedicated communication network.

(slide 11)

Special purpose communication networks designed to meet the needs of government, defense, security and law enforcement. These networks cannot be used to provide paid communication services, unless otherwise provided by the legislation of the Russian Federation. If the resources of these networks are insufficient, they are given a priority right to use, on a paid basis, the communication services of any communication operators, regardless of their functional and legal form and categories of communication networks.

Communication network- a set of technical means and distribution environment that ensure the transmission and distribution of information from many sources to many recipients.

Communication networks built on the basis of telecommunications are called telecommunication networks. Information transmission is carried out by multi-channel transmission systems, distribution - by switching stations.

In the literature, communication networks are classified according to their purpose, the nature of the formation and allocation of channels, types of switching, equipment and placement conditions, and degree of automation. Let us consider in more detail the classification characteristics of communication networks.

The classification of communication networks can be presented in the form of a diagram shown in Figure 2.

1.By purpose Communication networks are divided into two large groups:
- v Public communication networks
- v Restricted communication networks.

A public communication network is created to provide communication services to the population, various institutions, enterprises and organizations. From the laws of the Russian Federation: a public communication network is intended for the provision of paid telecommunication services to any user of communication services on the territory of the Russian Federation and includes telecommunication networks that are defined geographically within the service territory and numbering resource and are not defined geographically within the territory of the Russian Federation and numbering resource , as well as communication networks determined by the technology for implementing the provision of communication services

When building limited-use communication networks, specific requirements are implemented, determined by the nature of the activities of a particular department in whose interests this network is being created, and the possibility of subscribers connecting to the public network is also provided. Such networks include internal communication networks and long-distance communication networks. These are special purpose communication networks, dedicated communication networks.

Intra-industrial or technological communication networks: telecommunication networks of federal executive authorities, as well as enterprises, institutions and organizations, created to manage intra-industrial activities and technological processes that do not have access to the public communications network.

2. By the nature of formations and allocation of communication channels communication networks are divided into
v Primary
v Secondary.

Primary network- a set of standard physical circuits, standard transmission channels and network paths, formed on the basis of network nodes, network stations, terminal devices of the primary network and transmission lines connecting them. In this case, a typical physical circuit and a typical channel mean a physical circuit and a transmission channel, the parameters of which comply with accepted standards.

Network path- a standard group path or several series-connected standard group paths with path formation equipment switched on at the input and output.

Secondary communication network- a set of lines and communication channels formed on the basis of the primary network, stations and switching nodes or stations and switching nodes, providing a certain type of communication.

The main task of the primary network is the formation of standard channels and group communication paths, the task of the secondary network is the delivery of messages of a certain type from the source to the consumer.

The primary network, in turn, is classified according to territorial characteristics:

v the backbone primary network connects all regional, regional and republican centers of the country with channels of various types;
v intrazonal primary network is part of the primary network, limited to the territory of one zone, coinciding with the administrative boundaries of the region, territory, republic. In some cases, an intrazonal network may cover several areas and, conversely, there may be several intrazonal networks within one territorial unit;
v local primary networks - part of the network limited to the territory of a city or rural area. They provide the output of message transmission channels directly to the station and further to subscribers.
v zonal primary networks are a combination of intrazonal and local primary networks into one network.

The hierarchy of primary communication can be seen in Figure 3.

Figure 3 - Primary network hierarchy

3. Separation of primary and secondary communication networks based on territory coverage.

Depending on the territory served, networks can be local, corporate, national, or global (territorial). And also rural, urban, intraregional, local, intercity (backbone for the primary network), international.

Local communication network- a communication network located within a certain territory (enterprise, firm, etc.).

Corporate communication network- a communication network that unites the networks of individual enterprises (firms, organizations, joint-stock companies, etc.) on the scale of one or several states.

Intraregional or zonal communication network, - long-distance telecommunications network within the territory of one or more constituent entities of the Federation.

Backbone communication network- intercity telecommunication network between the center of the Russian Federation and the centers of the constituent entities of the Federation, as well as between the centers of the constituent entities of the Federation.

Intercity communication network - a communication network that provides communication between subscribers located on the territory of different constituent entities of the Russian Federation or different administrative regions of one constituent entity of the Russian Federation (except for districts within the city).

International communication network - a set of international stations and channels connecting them, providing international communications to subscribers of various national networks.

Local communication network - a telecommunication network formed within an administrative or otherwise defined territory, not related to regional communication networks; local networks are divided into rural and urban.

Rural communication network - a communication network that provides telephone communication in the territory of rural administrative districts.

Urban communication network - a network that serves the needs of a large city. The function of a city network is to act as a backbone for connecting local networks throughout the city.

National communications network - a communication network of a given country, providing communication between subscribers within that country and access to the international network.

Global (territorial) network communications unites networks located in different geographical areas of the globe. One example of such a network could be Internet.

4 . By service area Communication networks are divided into long-distance, international, local (rural, urban).

The main definitions are written in subparagraph 3.

5. Separation of networks according to the type of information transmitted. Based on the type of information transmitted, digital, analog and mixed communication networks are distinguished.

Analog communication is the transmission of a continuous signal.

Digital communication is the transfer of information in discrete form (digital form). A digital signal is analog in its physical nature, but the information transmitted with its help is determined by a finite set of signal levels. Numerical methods are used to process the digital signal.

The existence of mixed networks is typical during the transition from analog communication networks to digital ones.

6. Based on equipment and placement conditions, communication networks are divided into
v Mobile
v Stationary

Mobile refers to communication networks, the elements of which (CC, linear communication facilities) are located on a transport base and can be moved. One common type of mobile network is the military field communications network.

Fixed communication networks are created on the basis of communication nodes located in stationary structures. If necessary, fixed networks may include moving elements, for example, when replacing stationary elements that have failed for a short time, temporarily placing subscribers on moving objects, or the need to temporarily strengthen certain network elements.

7. According to the degree of automation, communication networks are divided into:
- v Manual
- v automated
- v Automatic.

On manual In communication networks, all or the vast majority of basic operations are performed by humans.

Automated are called networks in which the overwhelming number of functions for performing a certain volume of operations are carried out by a technical device.

Such networks are assessed by the degree of automation, which is determined by the coefficient Ka, equal to the ratio of the volume of operations performed by technical devices to the total volume of operations performed:

Where ns- the total volume of operations performed over a certain time, na- the number of operations performed by the machines.

Automatic networks provide for the performance of all functions for the transmission and switching of messages by automatic machines.

8. By type of switching networks are divided into switched, partially switched and non-switched.

For switched and partially switched Communication networks are characterized by the use of various switching options.

Long-term called switching, in which a permanent connection is established between two points on the network.

Operational called switching, in which a temporary connection is organized between two points on the network.

The combination of operational andlong-term switching assumes that in some sections of the information direction of the communication network long-term switching can be used, and in others operational switching.

Switched communication network- this is a secondary network that provides a connection at the request of a subscriber or in accordance with a given program through a telecommunication channel of terminal devices of a secondary network using switching stations and switching nodes during the transmission of messages. Transmission channels in switched networks are public channels. On partially switched communication networks, the use of all long-term and operational switching systems is provided. Really existing and projected communication networks in the near future belong to the class of partially switched ones.

TO non-switched communication networks These include secondary networks that provide long-term (permanent and temporary) connections of end devices (terminals) through a telecommunication channel using stations and switching nodes. Non-switched networks include the core communication network.

9.Separation networks by type of connection. Depending on the type of communication, communication networks are divided into telephone, videotelephone, telegraph, facsimile, data transmission, audio and television broadcasting networks.
v Telephone network- This is the most common type of operational communication. Network subscribers can be both individuals and legal entities - enterprises and organizations. It is used both for transmitting analog messages, as well as digital and text or graphic messages, so not only people, but also various hardware can be subscribers of the telephone network.

The operating principle of the telephone network is based on the transmission of an audio signal through electrical wires. The first telephone exchange opened in 1877 in Connecticut (USA). Telephone operators manually connected subscribers to each other. In 1833, telephone communication between Boston and New York was already opened. The first telephone lines were free, and only young men could work as telephone operators.

Today, the telephone network is a set of switching nodes, the role of which is performed by automatic telephone exchanges (automatic telephone exchanges), and connecting and communication channels.

v Broadcasting- organization and distribution of various messages to the population using systems, networks, and electrical communications. Broadcasting is a mass medium.

There is the following classification: sound and TV broadcasting - depending on the type of messages.

Sound broadcasting is the process of circular transmission of various sound information to a wide range of geographically dispersed listeners through a special set of technical means.

The primary television signal is also generated by the scanning method. The spectrum of the video signal depends on the nature of the image, and the energy spectrum is concentrated in the band f=0...6 MHz.

Moreover, color television is compatible with black and white television, i.e. a color image is received by black and white television and vice versa, color televisions perceive a black and white image.

v Telegraph networks are intended for transmitting (receiving) clear text messages (telegrams) or pre-encrypted ones (cryptograms). To organize telegraph communication, terminal devices such as telegraph devices and personal computers are used.
v Fax networks are intended for transmitting (receiving) messages in the form of printed, handwritten, graphic and other still images of flat originals with reproduction of their copies at the receiving point. In networks of this type of communication, special terminal devices are used - fax machines.
v Data network-- a system consisting of end devices (terminals) connected by data transmission channels and switching devices (network nodes), and intended for the exchange of information messages between all end devices.
10. Separation of networks by degree of security. Based on this criterion, communication networks are divided into protected (encrypted telephone networks, encrypted telegraph communications, etc.) and unprotected. In turn, secure networks can use equipment with guaranteed and temporary durability
11. Separation of networks by type of connection(equipment used). Based on the type of communication (equipment used), communication networks can be divided into wired (cable, airborne, fiber-optic) and radio networks (radio relay, tropospheric, satellite, meteor, ionospheric, etc.).

Wired communication lines include overhead communication lines (metal conductors, the laying of which is carried out openly, by tensioning them between supports-pillars with fixation on insulators) and cable communication lines (metal conductors, isolated from each other and from the environment, the laying of which is carried out openly , on the surface of something, or underground, under water, in sewer structures).

Advantages of wired communication networks:

v absence of mutual interference when laying together a large number of lines in a limited area (subject to certain laying rules);
v low level of self-interference in lines and channels of wired communication, which determines the relatively high quality of communication, ensuring reliability, timeliness and reliability of message transmission;
v relative secrecy of message transmission;
v in wired communications it is more difficult than in radio communications to deliberately interfere with the exchange of messages, etc.

Disadvantages of wired communication networks:

v the need for significant financial and material costs due to the need to organize and carry out expensive earthworks (especially in cities), the need to use expensive materials (non-ferrous metals, etc.);
v impossibility (increased complexity) of laying and operating lines in hard-to-reach areas (in wetlands, in the mountains);

the susceptibility of wire lines to destruction during natural and man-made emergency situations, as well as the possibility of their intentional damage.

Wireless communications (including radio communications) in the modern world play one of the leading roles in the process of transmitting and processing information. Some 100 years have passed since the first experiments in wireless telecommunications, but during this time the means and technologies of radio communications (wireless communications), as an integral part of scientific and technological progress, have penetrated into many areas of modern society.

Modern wireless communications, despite their small size and weight, are often quite complex technical devices that require qualified specialists to design such systems and maintain their high performance characteristics.

The advantages of wireless communication lines are obvious: they are cost-effective (no need to dig trenches to lay cables and rent land); low operating costs; high throughput and quality of digital communications; rapid deployment and change of network configuration; easy overcoming of obstacles - railways, rivers, mountains, etc.

Wireless communications in the radio range are limited by congestion and shortage of frequency range, insufficient secrecy, susceptibility to interference, including intentional interference and from adjacent channels, and increased power consumption. In addition, radio communications require lengthy approval and registration with the assignment of frequencies by the Gossvyaznadzor authorities (in our country the state authorized body), rent for the channel, and mandatory certification of radio equipment by the State Commission for Radio Frequencies.

Serious disadvantages of wireless communications are: relatively low throughput; poor signal transmission through walls, possibility of data interception or unregistered entry if additional security mechanisms are not used.

12. Also, all networks can be divided by type of topology.

The simplest communication network consists of two nodes and one branch (Fig. 4.)

Figure 4 - The simplest communication network

Such a network is called degenerate. More complex networks are characterized by spatial structure (or topology).

v The first topology is a common bus (SH) (Fig. 5)

Figure 5 - Common bus topology

Computer networks and technological information transmission networks in railway transport are built using this principle.

Advantages: simplicity (since one communication channel is used).

v Ring topology (Fig. 6)

Figure 6 - Ring topology

In a ring topology, information is transmitted in a circle, usually through road-level wired communications, computer networks, or circular call transmission.

Advantages: simplicity and higher reliability compared to a common bus.

The disadvantage is the installation of additional communication channels.

v Star or radial topology (Fig. 7)

Figure 7 - Radial topology

CUS - central communication center;

1, 2, 3 - peripheral communication nodes.

Based on the principle of star-shaped (radial) topology, wired, fiber-optic and radio communication systems are built.

Advantages: simplicity and good reliability.

v Fully connected topology (Fig. 8).

Figure 8 - Fully connected topology

The principle of fully connected topology is used in especially critical types of communications, as well as in some types of radio communications.

Advantages: high reliability, since even with the output of several communication channels, the network can function normally.

Disadvantages: high cost and length of communication channels.

v Tree or node topology (Fig. 9.)

Figure 9 - Tree topology

Many railway transport systems are built according to the principle of tree (nodal) topology.

Advantages: small number of channels with a large number of nodes.

13. Networks are differentiated based on the method of message delivery circuit-switched and storage networks (message-switched and packet-switched networks).

Circuit switched networks-- for transmission between terminal devices, a physical or logical channel is allocated, through which continuous transmission of information is possible throughout the entire communication session. The transmission route in such systems, as a rule, is determined when a communication session is established and does not change until the end. A circuit switched network is, for example, a telephone network. In such networks, it is possible to use nodes of a very simple organization, up to manual switching, but the disadvantage of such an organization is the inefficient use of communication channels or an increase in connection waiting time if the flow of information is inconsistent and unpredictable.

Packet switched networks- messages between nodes in such a network are transmitted in short bursts - packets that are switched independently and combined at the network node closest to the recipient. The vast majority of computer networks are built according to this scheme. This type of organization very effectively uses data transmission channels between network nodes, but requires more complex equipment of the nodes (implementing the division of messages into packets, their routing, temporary storage of packets, monitoring the fact of delivery to the recipient node and restoring messages from packets at the end node of the network), which predetermined its use in large information and telecommunication networks, an example of which is the Internet.