Classification of transport networks. Overview of technologies for the transport network (TS). Transport networks

To organize information exchange between individual local and global networks, a transport network (TS) is being deployed that implements services for transporting information flows between individual subscribers, as well as the provision of information services (such as radio, TV, facsimile communication, etc.) to consumers.

Transport communication network (backhaul) is a set of resources that perform transport functions in telecommunication networks. It includes not only transmission systems, but also related means of control, operational switching, redundancy, control.

Figure 13.1 - Telecommunication network consisting of a backbone transport network and subscribers connected to it through access networks

Typically, transport networks are deployed nationwide. In the Russian Federation, such a transport system is an interconnected communication networkRF (VSS).

The interconnected communication network of Russia today is a set of networks (Fig.13.2):

Public networks,

Departmental networks and communication networks for the benefit of government, defense, security and law enforcement.

At the same time, the main component of ARIA is public communication networks, open to all individuals and legal entities on the territory of Russia.

Figure 13.2 - Structure of the RF ARIA

Organizationally, WSS is a set of interconnected telecommunication networks run by various telecom operators as legal entities entitled to provide telecommunication services. The architecture of the RF VSS is shown in Fig. 13.3.

An interconnected communication network, as a communication system, is a hierarchical three-level system:

The first level is the primary transmission network, representing typical channels and multicast transmission paths for secondary networks;

The second level - secondary networks, i.e. switched and non-switched communication networks (telephone, documentary telecommunications, etc.),

Reliability of messages (correspondence of the received message to the transmitted one);

Reliability and stability of communication, i.e. the ability of the network to perform the transport function with the specified operational characteristics in everyday conditions,

When exposed to external destabilizing factors.

Communication systems can protect information from a number of threats to its security (blocking, unauthorized access to individual network elements, etc.). The responsibility for the general solution of information security issues (ensuring the properties of confidentiality, integrity and availability) rests with the user (owner of the information).

Communication network stability - this is its ability to maintain performance under the influence of various destabilizing factors. It is determined by the reliability, survivability and noise immunity of the network.

Various measures are used to increase the resilience of WSS networks:

Optimization of the topology of communication networks to simplify their adaptation to conditions arising from the impact of various destabilizing factors, including geopolitical;

Rational placement of communication facilities on the ground, taking into account the zones of possible destruction, floods, fires;

Application of special measures to protect networks and their elements from the influence of interference sources of various nature;

Development of reservation systems;

Implementation of automated control systems that organize work on restructuring and restoring networks, maintaining their performance in various conditions, etc.

13.6. Development stages of transport and telecommunication network technologies

Telecommunication systems have gone through several stages in their development (Figure 13.9). In fig. 13.9, the lower the layer corresponding to the technology lies, the more high-speed it is, and therefore it can provide the transfer of types of information of the overlying technologies. The transfer of information between secondary networks built on the basis of various telecommunication technologies is carried out using transitional elements called gateways, which are located at their borders.

At the first stage, the primary network was built on the basis of typical ASP channels and paths.

The second stage was characterized by the creation of digital transmission systems based on the hierarchy of plesiochronous digital systems that formed the primary digital network. At the same time, at both stages of development, the corresponding resource of the primary network was rigidly fixed in the form of standard channels and paths for the corresponding secondary networks. This approach, based on the rigid assignment of the resources of the primary network to the secondary communication networks, did not allow for the dynamic redistribution of the resources of the primary network under conditions of a non-stationary load of various types of information, was characterized by the use of different types of channel-forming and switching equipment and was not economically efficient. The existence of the mutual existence of the ASP and the DSP made it necessary to solve the problem of interfacing analog channels and paths with digital ones, which also led to an additional complication and increase in the cost of communication (modems, ADC-DAC, TMUX - transmultiplexers).

Figure 13.9 - Stages of development of telecommunication technologies

Secondary communication networks at these stages used, as a rule, cross switching, traditional switching of analog and digital channels, in telegraph communication networks, both channel switching and message switching were used, data transmission was carried out via non-switched and switched communication channels, as well as using the method packet switching. Video and television information was transmitted over dedicated broadband analogue or high-speed digital transmission paths, AAS and DSP, respectively.

The third stage in the development of telecommunication systems is associated with the emergence of new technologies for the transmission of information, both in the construction of a primary network and the use of new technologies of an integral type to build secondary networks.

At this stage, secondary networks provide in a single digital form the joint transmission of various types of information, carrying out a dynamic redistribution of the available resource between messages of different types of information. Moreover, within the framework of each technology of the secondary network, the same type of switching equipment is used.

The basis of the primary network of the third stage is made up of digital transmission systems of plesiochronous and synchronous hierarchies, which ensure the functioning of all secondary networks using various methods of operational switching: fast circuit switching, fast packet switching, frame, packet and cell switching.

Recently, with the development of telecommunication systems, the concept of communication networks of the next / new generation NGN (Next / New Generation Network).The NGN concept provides for the creation of a new multiservice network, while integrating existing services with it using distributed software switching (soft-switches).

The evolution of corporate networks from analog-to-digital to NGN architecture is illustrated in Fig. 13.10.

Figure 13.10 - Evolution of telecommunication network architecture

Next Generation Networks (NGN) are a new network concept that combines voice, quality of service (QoS) and switched networks with the benefits and efficiency of a packet-based network. NGNs mean the evolution of existing telecommunications networks, reflected in the convergence of networks and technologies. This provides a wide range of services, from classic telephony services to various data transmission services or a combination of them.

NGN concept - the concept of building next / new generation communication networks(Next / NewGeneration Network)providing an unlimited set of services with flexible settings for:

- management,

- personalization,

- creating new services by unifying network solutions,

Multiservice network - communication network, which is built in accordance with the NGN concept and provides an unlimited set of infocommunication services(VoIP, Internet, VPN, IPTV, VoD, etc.).

NGN network - a packet-switched network suitable for the provision of telecommunication services and for the use of multiple broadband transport technologies with QoS enabled, in which the service-related functions are independent of the applied technologies providing the transport.

NGN network capabilities:

- implementation of a universal transport network with distributed switching,

- transferring the functions of providing services to the terminal network nodes,

- integration with traditional communication networks.

NGN should have a wide range of capabilities - provide capabilities (infrastructure, protocols) for the purpose of creating, deploying and managing all possible types of services (known or not yet known). This concept includes services that use data of various types (for example, voice, video, text data, their various combinations and combinations with other types of data).

Transmission can be carried out with all types of coding schemes and data transmission technologies, for example, conversational transmissions, device-specific addressing, multicasting and broadcasting, messaging services, simple real-time and offline data transmission, with adjustable latency and delay resistant services. Services with different bandwidth requirements, with or without guaranteed bandwidth, must be supported taking into account the technical capabilities of the data transmission technology used.

In NGN networks, special attention is paid to the flexibility of the implementation of services in an effort to fully satisfy all customer requirements. In some cases, it is also possible to provide the user with the ability to customize the services they use. NGN must support open application programming interfaces to support service creation, provision and management.

Summarizing the above, we can say that the modern development of telecommunication communication networks occurs through the integration of all the functional capabilities embedded in the model of transport networks. Integration has led to the creation of universal multiservice transport platforms with electrical and optical interfaces, with electrical and optical switching of channels and packets (frames and cells), with the provision of all types of transport services, including services of automatically switched optical networks with signaling protocols based on a generalized switching protocol by GMPLS (Generalized Multi-Protocol Label Switching) labels.

In fig. 13.11 presents a generalized architecture of the transport platform, which indicates the possible sources of information load, negotiation protocols and transport technologies based on information from work.

Figure 13.11 - Generalized architecture of an optical multiservice transport platform

Legend in Fig. 13.11:

PDH, Plesiochronous Digital Hierarchy - plesiochronous digital hierarchy (speeds 2, 8, 34 and 140 Mbit / s);

N-ISDN, Narrowband Integrated Services Digital Network - narrowband digital network with integrated services (U-ISDN);

IP, Internet Protocol - Internet Protocol;

IPX, Internet Packet eXchange - internetwork exchange of packets;

MPLS, Multi-Protocol Label Switching - multi-protocol label switching;

GMPLS, Generalized MPLS - Generalized Label Switching Protocol;

SANs, Storage Area Networks - data storage networks (service servers, databases);

ISCSI, internet Small Computer System Interface - protocol for establishing interaction and management of storage systems, servers and clients;

HDTV, High-Definition Television - high definition television;

ESCON, Enterprise Systems Connection - connection of office systems (with databases, servers);

FICON, Fiber Connection - fiber connection for data transmission;

PPP, Point-to-Point Protocol - point-to-point protocol;

RPR, Resilient Packet Ring - self-healing packet ring protocol;

HDLC, High-level Data Link Control - high-level channel control protocol;

GFP, Generic Framing Procedure - general frame formation procedure.

PPP, RPR, HDLC, GFP protocols in transport networks perform the functions of matching information data from load sources with transport structures in order to increase the efficiency of using the resources of these structures, for example, high and low order virtual containers in the SDH network or optical channels in the OTN network, or physical resources of Ethernet transmission frames.

Transport network - a set of communication routes connecting settlements, respectively, of the country, region (city). The transport network is one of the most important elements characterizing the level of potential transport serviceability of a certain territory and the capacity of transport. The transport network of a country or a separate region is composed of railways and highways, sea and inland waterways, airways, trunk pipelines. To designate communication routes connecting the most important cities and industrial centers of a country or region, the term “ mainline transport».

In this sense non-mainline is industrial and urban transport. The paths for accessing warehouses, industrial enterprises, and other departmental facilities are called access roads.

Each type of land transport has waylaid along the surface of the earth. A strip of terrain is allocated for the path and arrangement of railways and highways, canals, pipelines, suspended roads and conveyors ( right of way).

Waterways - these are the ways of communication of sea and inland water transport. Sea routes - these are the routes followed by ships, mainly natural, for them berths, ports, sometimes an artificial fairway or canals are built. Inland waterways Are inland waters used for shipping and timber rafting. They can be natural (inland seas, lakes and rivers) and artificial (canals, artificial reservoirs, flooded rivers).

Airways are designed for aircraft flights, they connect the airspace of aerodromes and are limited by height and width; for takeoff and landing of airplanes and helicopters, aerodrome maintenance of flights, airports with the necessary infrastructure are equipped.

An obligatory element of the transport network is the initial, final and intermediate points, where freight and passenger flows are formed, disbanded and reorganized, they are called transport hubs... In transport hubs, cargo is prepared for shipment, consignments are formed, cargo is handed over to the carrier and from the carrier to the recipient, transfer from one mode of transport to another, short-term storage of goods, disbandment of consignments and other technological operations. The functions of transport hubs are expanding with the development of transport services. Loading and unloading points, which played the role of receiving, forming consignments and sending them to destinations, gradually transformed into terminals - where small-lot shipments are transformed into full-lot shipments for transportation in large lots. Terminals have become large cargo handling transport facilities with comprehensive mechanization of loading and unloading and warehouse operations; recently, the functions of terminals have been expanding due to freight forwarding, customs, exchange, information and other services related to goods movement. There is a new term for such nodes - " hubs».

The intensive development of international economic relations required new approaches to reduce the time for production and sale of products. A special place in this problem is occupied by cargo delivery speed... Differences in means of transportation and communication routes, infrastructure, control and management systems, regulatory and legal requirements in different countries lead to an increase in the cost of transporting goods in international traffic, often to a loss in the quality of goods and, as a result, to a loss of a sales market. The logistics approach to transportation systems has shown the need to create so-called corridors in the most significant directions of cargo movement.

Transport corridor – it is a collection of different types of transport working in the same direction taking into account freight and passenger traffic with a developed transport infrastructure of international class with the unification of requirements for technology, technology, information, legal relationshipsetc. Unified technical requirements, the introduction of advanced technologies and the creation of a single information space for the accompaniment and safety of the transport process are a condition for the efficiency of work in transport corridors.

A modern transport network must provide cost-effective aggregation of any client traffic and its reliable, high-quality transmission over communication channels. This can be achieved through a variety of transport technologies, many of which are more recent.

Widespread TDM technologies, based mainly on the principles of the synchronous SDH hierarchy (STM-N, VC-n, etc.), are being replaced by:

At the electrical level - Carrier Ethernet technologies (E / FE, GE, 10GE, 40GE and 100GE interfaces) and MPLS-Transport Profile. These technologies will provide ample opportunities for the creation of carrier-class packet-switched transport networks, oriented to the establishment of connections;

At the photonic level - technologies of the optical transport hierarchy OTH / OTN, similar to SDH, but unlike it, providing transparency of transmission and cross-switching of a set of TDM and packet traffic in any combination with their further transmission over channels of systems with channel division by wavelength optical radiation (systems with wavelength division multiplexing) - WDM.

IP / MPLS service networks can provide services by interconnecting with the systems of the core network of fixed and mobile operators, with points of presence of service providers, as well as with broadband access systems directly or over the carrier-class transport network. Packet switches with Carrier Ethernet / T-MPLS & MPLS-TP functionality become an important element of the transport layer of the network, interoperating on top of existing NG SDH / MSPP networks and / or transparent and flexible OTN / WDM photonic layer. The flexible automated WDM photon layer is equipped with software-configurable and reconfigurable optical I / O T & ROADM nodes. These and other solutions, including the use of intelligent transport technologies ASON / GMPLS (Intelligent Optical Core), must be scalable in performance and open to modernization.

Convergence of Transport Solutions and Ethernet Technologies: Evolution towards 40G and 100G

The IP transformation processes have spurred research to increase the capacity of transport networks for both traditional (TDM) and packet traffic.

For existing systems of the SDH synchronous transport hierarchy, transmission rates from STM-1 (155 Mbit / s) to STM-256 (40 Gbit / s) are standardized, increasing from level to level with a factor of 4. For optical transport hierarchy systems, transmission rates from OTU are standardized -1 (2.5 / 2.7 Gbps) to OTU-3 (40/43 Gbps), which also increase from layer to layer by a factor of 4. The Ethernet transmission speed (interfaces) grew by a factor of 10 and reached today 100 Gbps. The convergence of these technologies began with 10G transmission speeds. Research in recent years has shown that this convergence is moving towards 40G and 100G transmission rates. The current standardization supports this convergence and provides the promise of next generation networks.

The 40GE systems proposed initially for data collection and processing centers, as well as for corporate computer networks, are likely to be widely used at the level of transport networks with the introduction of a factor of 4, which is unusual for Ethernet technology (40GE in relation to 10GE). At the backbone level of the networks, the transmission speed of 100GE / OTN will be realized with a ratio of 2.5, which is unusual for transport networks, in relation to the 40GE / OTN level being introduced today.

Satisfying the requirements set by service providers is impossible without mastering data transfer rates in the range of up to 100 Gbps and higher.

Standards are currently being developed for the new 40G and 100G protocols and interfaces. Back in July 2006, the IEEE 802.3 WG created a special High Speed \u200b\u200bStudy Group (HSSG), which approved two MAC (Media Access Control) transmission rates a year later:

40GE for applications related to server-to-server communication, as well as servers and packet switches (server-to-switch);

100GE for switch-to-switch applications, including point-to-point connections between network clusters, etc.

The main efforts are directed to the selection of new technologies and solutions, including new methods of line coding, which will allow the most efficient transmission of high-speed digital streams of 40 Gb / s and 100 Gb / s over WDM systems, operating today mainly at speeds not exceeding 10 Gb / s (per each optical channel).

To increase the transmission range of 40 Gb / s and 100 Gb / s streams over WDM systems, multi-level linear codes (QAM, etc.), enhanced error correction codes (SFEC), as well as coherent reception methods will be used instead of differential signal detection. ... New methods are the future, but at the initial stages, 100-gigabit systems will be implemented with certain restrictions on the transmission range on WDM-systems already operating at the 10 Gbps level.

OTN / OTH transport solutions

Optical Transport Hierarchy (OTH), as defined in ITU Recommendations G.798 & G.709, provides methods for the placement, multiplexing and management of networks that support various client signals in their native format, regardless of the types of protocols used. The standard describes a single Optical Data Unit (ODU) / Digital wrapper structure, in which several existing frames of data streams can be placed, and then combined with other signals and then transmitted and controlled in a single style with a single functionality similar to that adopted in SDH systems.

The first version of OTH was focused primarily on SDH client signals. Therefore, initially in the recommendation G.709, only 3 fixed types of ODU containers were defined:

ODU 1 for CBR 2G 5 (STM -16);

ODU 2 for CBR 10G (STM -64);

ODU3 for CBR40G (STM-256).

OTH frameworks are currently being considered with respect to the transmission of client signals such as

Ethernet 1GE, 10GE WAN / LAN, 40GE, 100GE;

OTH 2.5G, 10G, 40G, 100G;

SDH 2.5G, 10G, 40G;

FC 1G, 2G, 4G, 8G (10G).

OTN technology is ideal for creating converged transport platforms that provide transparency in the transmission of traffic related to any service over optical channels of WDM systems, since it has its own separate header, similar to the SDH header, and allows you to monitor and control the network. Therefore, it supports transparent co-transmission of a combination of asynchronous (burst) and synchronous (TDM) traffic in any combination.

In addition, OTN systems:

Very effective in supporting asynchronous packet oriented services such as GE, 10GE, various Fiber Channel (FC), ESCON & FICON, which do not have their own physical layer monitoring;

Allow to detect and localize failures in the WDM-network, significantly improving the quality of services provided;

They are the only technology that can carry 10GE LAN PHY client signals widely used in IP / Ethernet;

They provide simultaneous transmission of synchronous and asynchronous signals over one optical lambda channel of the WDM system.

However, it should be noted that OTN standardization is not complete, in particular, the algorithm for placing GE, FC and Video has not yet been fully developed, transparent placement of 10GE is stipulated in parallel in several differing standards, for grouping and switching signals with transmission rates below 2.5 Gbit / s SDH systems are still used in practice. However, standardization continues, including the ODU4 / 100GE level and the ODUflex level for signal rates lower than ODU-1 (sub-lambda channels).

OTN technology has all the chances to become in the long term a universal transparent electrical layer of optical backbone communication networks, extending OAM methods well-developed in TDM / SDH to packet interfaces such as Ethernet (including 10GE LAN PHY), FC, ESCON, Digital Video, etc.

Role of ROADM at the photonic layer of the transport network

Reconfigurable Optical I / O Multiplexers (ROADMs) simplify the planning and maintenance of DWDM networks by automating (with minimal maintenance) the process of adding, removing, or redirecting optical channels. In existing networks, these processes are still carried out manually with the expenditure of significant efforts on equipment adaptation and traffic switching and require highly qualified personnel. The basis of ROADM is a new class of optical devices, namely Wavelength Selective Switch (WSS) with one input (group signal) and multiple outputs for groups and / or individual channels or with multiple inputs for groups and / or individual channels and one exit.

It should be noted that if a node performs input, output or rerouting / switching of a channel to another direction of transmission, then all connections between network nodes, including backhaul connections through a node at the photonic level, must maintain a delicate balance between the parameters of individual optical channels (wavelengths) to achieve optimal parameters in the transmission system as a whole. Therefore, the ROADM has the function of dynamically balancing the optical power levels of different optical channels.

As soon as transponders became available in WDM systems with the ability to tune the radiation wavelength in the entire C-band in accordance with the frequency grid with a step of 100 GHz and 50 GHz (up to 80-96 wavelengths of optical radiation in the C-band), a new one was discovered in ROADM limiting factor. Optical channels were output to fixed ROADM ports corresponding to a specific value of the optical radiation wavelength. Therefore, despite the flexibility of the transponders, it was not possible to avoid manual operations to switch the channel to new directions.

As a result of the research carried out to prevent blocking of the optical channel, a colorless ROADM device was proposed, in which any user port can be used to organize a channel with any wavelength of optical radiation. In the next step, directionless ROADMs were applied, in which an optical signal at any wavelength can be addressed to any port in any direction of transmission. Input / output of the corresponding channel in any direction is carried out automatically, without disturbing the balance in the remaining optical channels transmitted through the node through and through. This concept in Alcatel-Lucent's network solutions is called Zero Touch Photonic (ZTP) - a network reconfigurable through a control system, i.e. without "manual" personnel intervention at the nodes (Fig. 1).

The presence of colorless & directionless T & ROADM systems in the nodes of the WDM network is a prerequisite for the implementation of ASON / GMPLS functionality at the photonic level of the network.

ASON / GMPLS Intelligent Transport Solutions

Next-generation networks need to be more agile, resource efficient, and reliable and quality-of-service on demand. In other words, it is necessary to ensure the dynamic provision of network resources (necessary bandwidth) to deliver any service at any time to any user. This is why the IETF extended MPLS signaling and routing protocols beyond the IP network, and on this basis the General MultiProtocol Label Switching (GMPLS) was developed.

The GMPLS functionality with the distributed Control Plane separated from the Data Plaine is the next evolutionary step for MPLS technologies for use in transport networks. ITU-T has taken a deeper look at the networking aspects of this functionality in a series of recommendations for the Automatically Switched Optical Network (ASON). OIF has completed the standardization of network interfaces. UNI user interfaces are used to access the ASON network to request services, control connections, ensure QoS in accordance with SLA, collect failure messages, etc. NNI network interfaces are designed for communication between network elements, network domains, and different networks. At this level, within the Control Plane, requests for connections are processed, they are organized and monitored, information is exchanged in certain volumes about available resources in network elements and connections, services are routed between network domains, etc.

One of the main advantages of an intelligent transport network with ASON functionality is the ability, upon user demand or a request from a centralized network management system, to automatically set:

Connections within a network built on equipment from one supplier;

End-to-end connections on a network built not only on equipment from different vendors, but also using different functional and technological layers focused on establishing connections, such as SONET / SDH (VC-N), WDM / OTN (OCH, ODU), T-MPLS / MPLS-TP (LSP, PW3) etc.

To implement ASON / GMPLS at the photonic level, T & ROADM systems are placed at the nodes of the WDM network, providing switching of optical channels without additional O-E-O conversion. If T & ROADM systems have a connectivity coefficient N up to 6-10 (the number of directions to which an optical channel can be switched from one network node at the photonic level), then in this case there is no need to keep free up to 50% of the network capacity to implement protective mechanisms with full redundancy channels like O-SNCP, OCP, etc. It is enough to have 10-25% of the allocated free capacity on the links in the network to provide the ability to bypass the affected areas based on ASON / GMPLS.

These nodes can also host automatic path switching systems operating in accordance with the OTH / OTN standard at the electrical level and providing transparent data switching at the ODU and / or sub-lambda-channels (ODUflex) level, including GE, 10/100 Ethernet, Fiber Channel, FICON / ESCON, SONET / SDH, etc. ASON / GMPLS technology can be implemented at the OTH / OTN network level (Fig. 2).

SDH-level ASON / GMPLS functionality has already been implemented on many networks. Similar functionality at the photonic level, providing automatic recovery (without intervention of the operator of the control system) optical lambda channels in the event of network failures, is implemented in the 1626LM equipment and will begin to be implemented on operators' networks in 2010.

To category: Partnerships

Transport links

When organizing a horticultural partnership, it is very important to provide a rational solution to the main and secondary transport links. The main transport links are electric trains, shuttle buses, personal transport. All this transport passes along the already laid highways. It is to them that the territories allocated for gardening associations are tied. The distance from the main highways to the sections should be no more than 3 km. Secondary transport links are local roads that directly connect a highway or a railway station with a gardening partnership, as well as driveways on its territory.

For the convenience of access to each site, the entire territory is divided into sectors, covering two rows of sites. Main passages 6-8 m wide are laid between the sectors (carriageway 2.5-3.5 m, shoulders 1.5-2 m each), and perpendicular to them after about 400 m (no more) - transverse passages of the same width. On the main driveways, in the middle between the transverse ones, traveling platforms are arranged with a length of 14 and a width of 7 m (at least). A bypass path 1.5 m wide is provided along the common fence.If the gardening partnership includes more than 50 sites, then at least two entrances to the territory should be arranged. The width of the gate should be 4.5, wickets - 1 m.

Access roads and main driveways on the site are made of local materials - sand, gravel, dolomite, slag, etc. Along the roadway, ditches up to 0.5-0.6 m deep are arranged for storm water drainage.

An important aspect of the improvement of the territory is the creation of transport parking lots and turning platforms (Fig. 3.). They are usually located at the end of streets or driveways for easy maneuvering when driving around and out of cars. Parking lots can be located at the main entrance to the territory. However, gardeners often prefer to park the car on their site, although this requires a fairly large area. In this case, it is more convenient to place the parking lot under the terrace or in the basement.

Figure: 1. Examples of the device of turning dead ends and parking lots (dimensions in meters)

Layout of garden plots (Fig. 2). When dividing the territory into separate sections, they usually strive to ensure that they occupy the shortest possible length along the street, which reduces the cost of installing roads, utilities, etc. For development, separate or blocked houses are used. It is possible to improve the layout of the plots and introduce variety into the building by arranging dead-end and looped entrances to the houses located indented from the street. Houses can be placed in relation to the street with short or long facades. Loop and dead-end construction methods allow reducing the length of streets and utilities by 15-30% and at the same time significantly improve the architectural and artistic qualities of the entire territory. Group placement of garden houses around a small enclosed courtyard creates good protective conditions from the winds. On the resulting closed courtyard, you can organize a playground with sports equipment or a common resting place for a group of gardeners.

The layout of a small garden plot should be thoughtful and economical. It can be divided into three parts: a garden and vegetable garden area, which occupies 60-65% of the area; recreation area, including a garden house - 20-25%; the area of \u200b\u200bthe utility yard with buildings - 10-15%. In each individual case, the peculiarities of the site should be taken into account: its area, shape, relief, direction of prevailing winds, orientation relative to the cardinal points, the presence of vegetation, a reservoir, etc.

The garden and vegetable garden area should be located in the southern or southeastern part of the site. The main organizing axis of the garden is the path leading from the house (0.5-0.6 m wide). An irrigation pipeline is being laid next to it. Along the perimeter of the site at a distance of 1 m from the borders, you can plant a number of berry bushes - gooseberries, red and white currants (in a row after 1.5 m), black currants, raspberries (in a row after 1 m).

Figure: 2. Examples of building gardening associations with separate and blocked houses: a - separate houses along the street; b - the same, staggered; c - blocked houses along the street; d-the same, in a checkerboard pattern; d - loop building; e - dead-end buildings

It is impractical to plant berry bushes at the same time. It is better to do this in four steps (after 2-3 years), thereby creating a berry turnover, in which a fourth of the area intended for them is set aside for preparation for planting, another of the same part - for young bushes, the same amount - for fruit-bearing ones, and the rest - under those already in the stage of completion of fruiting. This will guarantee an even flow of crops, greater reliability from freezing and less damage to shrubs by pests and diseases.

On one side of the site, stepping back 3 m from the berry bushes, you can place a row (or two) apple trees. These tall and racy trees are placed 4 m from the border so that they do not obscure the adjacent area. They are also planted in a row every 4 m. Stone trees (cherry, plum, sweet cherry, cherry plum) are planted in a row every 3 m.

Free space is allocated for the cultivation of garden strawberries (strawberries), vegetables, green crops and potatoes. This area is divided into 8-10 plots and a vegetable-strawberry crop rotation is established. As a result, the location of each crop changes periodically, which is very important for the rational use of nutrients in the soil and protecting plants from pests and diseases, and ultimately for obtaining a higher yield for each crop. The alternation in the crop rotation can be as follows: first, radish, lettuce, dill, parsley. Following their harvesting, garden strawberries are planted with different periods of fruiting. Then potatoes, cucumbers, tomatoes, carrots, beets, onions, garlic, peas can be planted.

It is advisable to practice mixed and compacted crops. At the same time, cultures are selected taking into account their individual characteristics and mutual influence on each other. Neighborhood plants can be beneficial or harmful. For example, cucumbers are friends with peas, cabbage, but they are at enmity with potatoes. White cabbage recognizes dill, celery, onions, lettuce, potatoes as neighbors and dislikes tomatoes and beans. Carrots go well with tomatoes and peas. Potatoes get along with beans, cabbage, horseradish and onions, but they do not tolerate tomatoes and cucumbers.

The breakdown of a garden and a vegetable garden, of course, is an individual matter, and here a lot depends on the needs of the gardener, local and natural conditions, but the principles of proper agricultural technology should still be guided by. Then the plants get sick less, bear fruit better. Every amateur gardener can read about this in the special agrotechnical literature (see the list of recommended literature at the end of the book).

When choosing a site for the construction of a garden house, in addition to local conditions (wind direction, sunlight, relief), one should also take into account the nature of the construction of neighboring sites. The house is placed at least 3 m away from the road. It is positioned so that the distance between neighboring houses in the longitudinal and transverse directions is at least 12 m. When the houses are blocked, there must be a 15-meter gap between each pair.

Since the shade from the buildings makes it difficult for plants to grow, the house should be built compact. When entering the site from the north, it is better to place it at the beginning of the site, and from the south, in the depths. It is beneficial to move the house from the axis of the plot towards the fall of the shadow. Usually it has a facade to the road and parallel to it, but it is not necessary to strictly follow this rule. He can even stand at an angle to her. If the site is oriented towards the road with the north side, it is better to turn the house in this direction with a side facade.

The recreation area, like no other, reflects the tastes and favorite activities of people. It is formed, as a rule, near the house, continuing the terrace, which, as it were, gives additional reserves of living space. Skillfully equipped, it can usefully be adapted to various activities. Some are fond of floriculture and want to create a rich collection of flowers, others like to sit by the water and place a beautifully made pond here, others prefer to do creative work outdoors, for example, carpentry, and adapt the entire site for this activity. If the family has small children, you can make a small corner for games - hang up a swing, arrange a sandbox, etc., and for older children, organize a playground (horizontal bar, log, etc.). The recreation area can be created easily reconstructed due to portable furniture and the organization of temporary leisure activities. A good resting area would be a green lawn interspersed with stone slabs, or an ornamental garden decorated with a group of flowering bushes, or decorative screens - lattices braided with lianas (Fig. 3).

The small space of the recreation area should not be cluttered with small forms. We must strive for their simple and natural design, take care of natural elements if they are on the site: stones, relief, plants. It is good if one or two trees grow on a green lawn, under the shade of which it is convenient to place garden furniture - a table, benches, a chaise longue, etc. (Fig. 3).

One of the main requirements for the location of the house on the site is its convenient interconnection with all zones and, first of all, with the economic one, which is made up of the utility yard, greenhouse, barn, cellar, outdoor shower, toilet. They must be located on the opposite side of the road. They can be built either as free-standing ones, or they can be blocked with each other or with the outbuildings of a neighboring site.

Figure: 4. Garden furniture

For breeding birds or rabbits in the yard, a walking area should be provided, be sure to fence it off. Here, by the barn, a site for building materials should be set aside. Another area (15-20 m2) should be provided on the side of the roadway (for imported fertilizer, sand, fuel, for parking the car).

It is also possible to block outbuildings with a house. This allows for more rational use of the land and greater comfort. The architectural appearance of the garden house will also benefit. However, in this case, ventilation should be provided for the sanitary and storage rooms. When an extension to the blank walls of a house or to summer rooms (terrace, veranda), it is better to place the entrance to the outbuildings on the side opposite to the entrance to the housing and recreation area. Greenhouses can be attached to the house, from the south or south-east side.

Sports and playgrounds should be arranged in places protected from the prevailing winds. They must be dry (with a groundwater level of at least 0.7 m from the planned surface) and be no closer than 15-18 m from outbuildings, roads, streets, garden houses. Playgrounds are usually rectangular in shape, however, depending on local conditions, their configuration may vary. The land plot allocated for the sports and game complex is fenced off with tree-ornamental plants. The lawn here should be made of trample-resistant grass mixtures. Other coatings are also acceptable. Drainage is carried out by surface runoff due to the slope of the surface towards the driveways.

Figure: 8. Playground equipment

Shared playgrounds in a gardening partnership are also necessary, because children spend almost all day outdoors. When organizing such sites, it is necessary to take into account a number of factors - proper sun lighting, proximity to home and good visibility. In the hot time of the day, such a site should be shaded., And in the morning and evening hours - illuminated by the sun. The main thing on the playground is play equipment, intricate, comfortable and beautiful. Here, like nowhere else, you can show imagination, imagination and taste.

Let's consider one of the options for equipping a playground (Fig. 7). The simplest and most necessary play equipment is a sandbox and a table with benches. They represent, as it were, a single whole. The sandbox barrier is made of round timber dug vertically into the ground. Slabs or trims of boards are also used for this. The sandbox in this version has a square shape, but it can have any other.

On the site, in addition to a sandbox and a table with a bench, ladders, swings, slides and other equipment for games can be installed. A pergola entwined with plants will create an openwork shadow and illusoryly close the area. After the playground equipment is ready, it needs to be painted with bright, cheerful colors.

The technical basis for the construction of transport networks are telecommunication systems for the transmission of the Synchronous Digital Hierarchy (SDH). Their introduction on communication networks began in the 80s of the XX century. The fundamental difference between SDH systems and pre-existing digital transmission systems is that they are not "producers" of information, but are intended only for highly efficient transmission and distribution of digital streams formed as in traditional structures of the standard plesiochronous digital hierarchy (PDH), and in new telecommunication technologies - ATM, B-ISDN, etc. All of the above digital streams are "transported" in SDH systems in the form of information structures called virtual containers (Virtual Container - VC). In VC structures, the original digital information is carried over the transport network, supplemented by a certain number of service information channels, called path headers (Path Overheard - RON). In the general case, additional channels are designed for efficient management of the transport network and perform the functions of transferring operational, administrative and service information (Operation, Administration, Maintenance, OAM). This provides high functionality and high reliability of the communication network.

Groups of the same or different types of VCs are transmitted between the elements of the transport network (from the sender of information to the recipient) along transmission lines in the form of information structures, called synchronous transport modules Synchronous Transport Module - STM). STM is "transported" at different bit rates corresponding to different STM-1, 4, 16, 64 ordering. STM-Ns are equipped with appropriate headers to provide full OAM STM transmission within the Regeneration Section OH (RSOH) and multiplex section (Multiplex Section OH-MSOH). A simplified functional diagram of the SDH transmission system, which is the main structural link of the transport network, is shown in Fig. 2.1.

Figure: 2.1. Functional diagram of the SDH transmission system

The figure shows two types of sections, which are called "Regeneration section" and "Multiplexer section".

A "regeneration section" is a segment of the transmission system between the terminal equipment of a network element, in which the STM-N signal is transmitted or received by both the regenerator, or between two adjacent regenerators.

A "multiplexer section" is a means of transferring information between two network elements, in one of which an STM-N signal is generated (collected), and in the other it is "parsed" to component streams. In general, the SDH transport network consists of multiplexer sections, for which the SDH signal level may be different depending on the required transmission channel capacity for each section.

"Tract" – means a logical connection between the point in the SDH transmission system at which the VC virtual container is "assembled" (eg, from PDH component streams) and the point at which the VC is "parsed". The path can be thought of as a pipe laid through multiplexer sections, directly connecting two points between which information is transmitted. For the "transportation" of various volumes of digital information, virtual containers of various types have been developed. For European PDH streams, these are:

Low order VC (LOVC);

VC-12 for "transporting" E1 \u003d 2048 Kbps (2 M);

VC-22 for "transportation" E2 \u003d 8448 Kbps (8 M);

Higher order VC (High order VC, HOVC);

VC-3 for "transportation" ЕЗ \u003d 34368 Kbps (34 М);

VC-4 for "transportation" E4 \u003d 139264 kbps (140 M).

Depending on the "capacity" of the virtual container, VC-12, VC-22 (lower order) paths and VC-3, VC-4 (higher order) virtual containers paths are distinguished.

A virtual container is an elementary unit of information processed in the SDH transport system during multiplexing, cross-connections (cross-connection), etc. In this case, there is no need to access the "transported" information, since different information is presented in the same form, which is called virtual containers (at the same time, the information necessary for processing it along the way is added to the VC).

As mentioned above, virtual containers are transferred between the elements of the transport network in the form of STMs of various orders. The main (primary) structure for receiving STM streams is STM-1 with a normalized transmission rate of 155.52 Mbit / s. At the same time, depending on the needs of the network, in the STM-1 digital stream, it is possible to transfer virtual containers of various types and in various combinations:

Higher order STMs can be obtained from STM-1 digital stream by simple synchronous multiplexing according to the recommendation G.707 of the telecommunication sector of the International Telecommunication Union (ITU-T):

Moreover, multiplexing, starting with STM-4, is carried out in the optical range.

STM-N information structures are transmitted between the elements of the transport network via transmission lines organized over fiber-optic communication cables, satellite lines or digital radio relay lines (taking into account the multiplexing peculiarities, only the STM-1 digital stream can be transmitted in electrical form via the DRL).

A characteristic feature of the SDH transport systems shown in Fig. 2.1, is a high degree of redundancy of both line paths and the main nodes of multiplexer equipment. So, transmission lines between network elements are usually fully redundant (Fig. 2.1), which allows avoiding the loss of huge flows of information in case of accidents (for example, even in the primary STM-1 stream, traffic of 1920 PM channels can be transmitted in the mode of "transporting" a stream of 140 M) ...

An example of building a fragment of a transport network using SDH transmission systems is shown in Fig. 2.2. As can be seen from the figure, the transport network is designed to transmit any information messages in digital form. At its core, a transport network is a collection of switching nodes, input points for individual digital streams, transmission lines with regenerators and multiplexers. At all nodes of the transport network, it is possible to switch paths for the output and input of information flows. In addition, at the nodes of the network, paths can be switched in the event of damage to the transmission line or equipment.

Figure: 2.2. Fragment of a transport network using SDH transmission systems