13.1. Interconnected communication network of the Russian Federation - national transport backbone network
For the organization information exchange a transport network (TS) is deployed between individual local and global networks, which implements services for transporting information flows between individual subscribers, as well as providing information services(such as: radio, TV, fax, 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 network RF (VSS).
The interconnected communication network of Russia today is a set of networks (Fig.13.2):
Networks common use,
Departmental networks and communication networks for the benefit of management, 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 given performance 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 on individual network elements, etc.). 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 automated systems management organizing work on restructuring and restoring networks, maintaining their performance in different conditions and etc.
13.6. Stages of development of technologies for transport and telecommunication networks
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 higher-lying technologies. The transfer of information between secondary networks, built on the basis of various telecommunication technologies, is carried out using transition 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 phase was characterized by the creation digital systems transmissions 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 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 presence of the mutual existence of the ASP and the DSP made it necessary to solve the problem of interfacing with each other analog channels and paths with digital, 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 analog 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 for the construction of 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 various types of information. At the same time, 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 formed by digital transmission systems of plesiochronous and synchronous hierarchies, which ensure the functioning of all secondary networks using different methods operational switching: fast channel 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. Thanks to this, a wide range of services is provided, from classic telephony services to various services data transmission or a combination thereof.
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,
- creation of 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 transport technologies.
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 must have a wide range capabilities - to 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, etc. various combinations and combinations with other data types).
Transmission can be carried out with all types of coding schemes and data transmission technologies, for example, dialog transmissions, with addressing specific device, multicast and broadcast, messaging services, simple real-time data transmission and offline, latency throttling and latency resilient services. Services with varying bandwidth requirements, with or without guaranteed bandwidth, should be supported taking into account technical capabilities used data transmission technology.
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 modern development telecommunication communication networks occurs through the integration of all the functionalities 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 specifies possible sources information load, coordination protocols and transport technologies for information from work.
Figure 13.11 - Generalized architecture of an optical multiservice transport platform
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 coordinating 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 networks that form wired communication channels between remote wireless networks are a set (Fig. 1.5):
- wired communication lines (links) through which digital electrical or optical signals are transmitted;
- network nodes that relay signals (including their multiplexing / demultiplexing) from one wire line to another by means of switches (Figure 1.5 shows the structure of a transport network containing 9 switches interconnected by 15 communication lines).
Modern transport networks are related technical systems, detailed information about which constitutes a separate area of knowledge. Brief information about the characteristics of these networks, related to the subsequent presentation of information about the BWN, are as follows (Fig. 1.6).
1. The hierarchical level of network implementation serves as the basis for their division into two types - primary and superimposed networks.
Primary networks (transmission system) provide physical transfer electrical signals from the source to the end node of the transport network. One of the important functions of primary networks is the multiplexing / demultiplexing of signals various sources... The digital form of the signal, which is used in modern transport networks, corresponds to time division multiplexing (Time Division Multiplexing -
TDM). By the way of synchronization of multiplexed signals distinguish the following types of primary networks:
- networks with a plesiochronous digital hierarchy (PDH), in which the multiplexed signals are close to synchronous, but not strictly synchronous; such networks provide transfer rates digital signals up to 150 Mbit / s;
- networks with a synchronous digital hierarchy (SDH) in which the synchronization of multiplexed signals is ensured - such networks provide a digital signal transmission rate of up to 10 Gbit / s.
Rice. 1.5. Transport network structure
Obviously, the transfer rates of information flows in both types of networks allow creating on their basis a transport infrastructure that meets the needs of the deployment of modern BWNs.
Overlay Networks based on primary networks provide channel shaping wired communication and transferring messages between input and output nodes. Overlay networks supplement the primary networks with all the resources needed to provide wired signal transport. The most common types of superimposed networks: - public switched telephone network (PSTN), designed to provide channels with a bit rate of up to 64 kbps digital streams; such channels are called basic digital channels(Digital Signal 0 - DS0 or Bearer channel - channel);
- a digital network with integrated services (Integrated Services Digital Network), designed to provide 23 basic digital channels in the United States, and 30 - v Europe (aggregate data rates respectively equal to 1.544 Mbps and 2.048 Mbps);
switched data transmission network (Public Switched Data Network - PSDN) intended for the implementation of packet data transmission; an example of such a network is the Internet.
Rice. 1.6. Transport network classification criteria
2. Method of transmission of messages. According to the method of message transmission, all transport networks are classified according to two criteria: the form of presentation of messages in the time domain and the method of interconnection of subscribers in the process of information exchange.
In terms of time representation, the message can be continuous (circuit mode) or packet (packet mode). The continuous form is characterized by the indivisibility of the message during the communication session, the batch, on the contrary, by dividing it into parts, each of which is transmitted separately (with the subsequent restoration of the message integrity by combining all parts in the proper order by the recipient's node). The continuity of the message is equivalent to the establishment of a closed line between the source and destination nodes of the transport network electrical communication(circuit),
which explains the origin of the English term for designations nepp breakout transmission. Message packaging is combined with two ways packet transmission - either over a single electric line,unchanged for all packets of the message, or by means of independent transmission of each packet by the transport network, which in this case are called datagrams.
The form of the relationship of subscribers during the transport of messages is determined by the presence / absence of a preliminary agreement of the contacting parties about the exchange of messages. There are two types of subscriber communication:
- connection oriented communication, corresponding to the transport of messages along a path unchanged throughout the communication session - the establishment of the path precedes the transmission of the message (for example, over the lines' connecting nodes 1 - 4 - 5 - 9 in Fig. 1.5);
- communication without connection (connectionless oriented), in which the transport of messages by the network is carried out without prior establishment of the route of its transmission; implies the possibility of passing different packets / parts of the message in different ways (for example, in the network shown in Fig. 1.5, when transmitting a message between nodes 1-9, it is possible to transmit one packet through nodes 4-5, another - through nodes 7-8, a third - through nodes 2-3).
Connectionless transmission can only be carried out in packet (datagram) form; continuous message transmission - only when a connection is established in the transport network; batch messages may imply connectivity, but not connect. An example of connection-oriented packet transmission is the transmission of IP packets over the PSTN and ISDN networks.
3. Communication channels of the transport network are usually classified based on the form of implementation of the connection between the end nodes of the line and the bandwidth of the channels.
Implementation of the connection between nodes can be both "physical" and virtual.
The physical connection is accomplished by forming a concatenated line that includes a number of point-to-point inter-nodal lines and switches connecting them with a fixed direction of switching from incoming to outgoing inter-nodal line. For example, the physical connection of nodes 3 and 7 in Fig. 1.5 is formed by creating a compound line that includes nodes 3, 5, 6, 7 and three inter-node segments. Typical example transport networks with physical circuit mode can be PSTN and ISDN.
The virtual implementation of the connection consists in packet transmission of messages with the same route in the transport network (i.e., with the same list of nodes and connecting lines). The persistence of the route is ensured by storing the direction of transmission of packets (packet switching) in the switches of the network. Memorization is carried out either only for the time of message transmission, which corresponds to the concept of a switched virtual circuit, or for a long time, which corresponds to the concept of a permanent virtual channel.
Creation of dial-up channels is carried out at the request of the source of the message automatically, creating permanent channels- network administrator. Examples virtual networks are PSDN networks.
The channel capacity, which is understood as the capability of the latter to carry information over a certain period of time, is determined by the type of cable lines used and the features of signal multiplexing in switches. In modern transport networks, cables are used with two types of guiding media (wire copper and fiber optic) and the two multiplexing methods mentioned above - plesiochronous (PDH) and synchronous (SDH). Typical (but not required) is a combination of wired copper lines using PDH and fiber-optic lines using SDH. The first combination corresponds to a throughput of up to 150 Mbit / s, the second - up to 10 Gbit / s. The synchronous multiplexing technology allows the latter to be “superstructured” over the plesiochronous one: thus, slower lines with plesiochronous digital streams can be connected to faster lines with synchronous streams.
Digital streams of plesiochronous network technology are standardized in three standard options: European (Ex), American (Tx) and Japanese (Jx). Despite the general principles, each of them uses various ratios multiplexing at different levels of hierarchies. Each of the standards covers several levels of the digital hierarchy and has several symbols that describe specifications interface and corresponding baud rate:
- Ex standards, in accordance with the values of the provided data transmission rates, denoted by the symbols E0, El, E2, EZ, E4, E5;
- Tx standards, designated Tl, T2, TK, T4 and T5 (adopted in the USA, Japan and Korea);
- Jx standards, denoted by Jl, J2, J3, J4, J5, although another designation is more common: DS1, DS2, DS3, DS4, DS5, which appeared as a result of the harmonization of the Japanese and American versions of standards due to the similarity of their characteristics (the actual similarity takes place for the first two hierarchical levels).
The basic digital streams of both standards - E0 and DS0 - correspond to the same values data transfer rates - 64 kbps. The hierarchy of the rates of digital streams of the E- and T-versions is given in table. 1.1. In practice, digital lines El, T1 and EZ, TZ,
SDH systems conforming to international standards for synchronous primary transport networks and SONET (Synchronous Opti< Network), отвечающие стандартам США, обеспечивают мультиплексирован цифровых потоков со скоростями порядка сотен и тысяч Мбит/с, что на one-j order exceeds the values of speeds in plesiochronous systems. Partial overlap of the standardized digital stream rate values of the two varieties corresponds to the upper hierarchical PDH levels and the lower hierarchical SDH levels. The base STM-0 value of the Synchronous Transport Mode (STM) rate corresponds to a bit rate of 48.96 Mbps. Information about the data transfer rates of higher levels (STM-x) are presented in table. 1.2.
Fiber-optic cables provide informational noroi transmission at speeds up to 10 Gbit / s, which complies with the STM-64 standard (5th level of the speed hierarchy). Differences in payload transmission rates (paylo; and the total line rate)
