SDH NETWORK MANAGEMENT BASES

1. A brief introduction to network management

1.1. Basic concepts and objectives of the control system

The purpose of the SDH network, like any communication network, is to serve consumers, or customers, for example, by telephone. At the same time, not only services should be provided to subscribers, but also the quality of communication should be ensured, i.e., timely and accurate message transmission should be guaranteed, the required connections and signaling should be made, protection from losses and interruptions during the communication session should be provided, etc.

The functioning of the network with the specified requirements is impossible without its maintenance at various levels with the help of a flexible standardized management system. In the general case, network maintenance is reduced to automatic, semi-automatic or manual network management, its testing and collection of statistics on the passage of signals that occur in unusual or emergency situations, as well as to network management or administration. In turn, these functions cannot be carried out without various kinds of signaling about network conditions, for example, signaling of an emergency condition in multiplexers, cross-connectors, regenerators, etc. Signaling should be carried out through special built-in or reserved service channels for this, which connect the control (operating on a network) OS systems (Operations Systems) and managed objects MO (Managed Objects), or elements of the NE network.

The first and main task of the network management system is to ensure that the quality of the services that the network offers its customers meets the specifications. The subscriber pays for the quality services provided to him during the communication session and he will receive the appropriate service from the network, with the exception of minor quality losses caused by some network operation errors. The true result of network management is to reduce (minimize) errors (omissions, interruptions, overflows, etc.) in accordance with the prescribed quality of service to consumers.

The second task of the control system is to distribute the information (load) digital stream (traffic) passing through the network in such a way that the consumer can serve the minimum amount of equipment involved in the network without affecting (pressure) the load and providing a “backup route” in case of emergency situations failure (failure) of any network element.

Thus, the general problem of the functioning of the network management system can be formulated with the following expression: “The management system in SDH networks should serve the maximum number of calls while fully ensuring the quality of services provided to consumers and be most effective in terms of price” [108]. Therefore, it is not surprising that the control system in SDH networks is considered as their integral part.

To solve the indicated tasks of the control system at all its levels (physical, logical, informational and administrative), of which the last two are classified as a special category of management - management, it is necessary to develop a model of the control network and describe the types of communication interfaces needed to implement the functions of the control system at different parts of the network [77].

Unlike plesiochronous DSPs, which practically do not have a standard description of network models and interfaces, as well as special control communication channels, SDH transmission systems contain their own control system (for more details, see subsection 5.3). It is based on the currently well developed system of standards presented in ITU-T Recommendations of the M series [148 - 154], which describes the models of control networks, interaction interfaces, function blocks and control channels.

Further, from a practical point of view, only the main aspects of the SDH network management system are considered. The construction of the management network structure, which should reflect its main ideas and capabilities, will be based on relevant ITU-T recommendations.

Currently, the most popular in the world is open network architecture, which is based on the reference model for the interaction of open systems - EM BOC, or in the English abbreviation RM OSI (Open Systems Interconnection / Reference Model), which for short will be referred to as the OSI model [77 , 80]. In presenting the material in this section, OSI model standards and protocols were also used.