7.5 TMN protocol hierarchy

This Pyramid - Logical Layered Architecture (LLA) classifies tasks according to the complexity of managed elements (from individual devices on a network to intercorporate networks). The pyramid of levels of the TMN control system is shown in Fig. 7.4.

Fig. 7.4. Levels of network management system

The figure conventionally shows the components of each level and their possible relationships. Consider them, starting with the lower level.

The network element layer (NEL - Network Element Layer) plays the role of an interface between, as a rule, a database with management information base (MIB - Management Information Base) located on a separate device and the TMN infrastructure. This database refers to such network elements as, for example, switching stations, transmission systems, multiplexers, sets of test equipment. It includes Q-adapters and the actual network elements that coordinate the work of the communication network and TMN.

The Element Management Layer (EML) corresponds to the Functional Support Systems (OSS) that control the operation of groups of network elements. This level allows you to manage groups of network elements. At this level, control functions are implemented that are specific to the equipment of a particular manufacturer, and this specificity is masked from the levels above. Examples of such functions are hardware error detection, power consumption and operating temperature monitoring, statistical data collection, measurement of the utilization of computing resources, and updating of firmware. This level includes intermediary devices (although physically they may belong to higher levels) interacting with the OSS via the q ₃ interface.

Network Management Layer (NML - Network Management Layer) forms the representation of the network as a whole, based on data about individual network elements that are transmitted by the support systems of the previous level operations through the q3 interface and are not tied to the features of products of a particular company. In other words, at this level, monitoring of the interaction of network elements is carried out, in particular, data transmission routes are formed between the terminal equipment to achieve the required quality of service (QoS), changes are made to the routing tables, the throughput of individual channels, routes and routes is monitored, network performance is optimized and identified failures in her work.

The Service Management Layer (SML) covers the aspects of network operation that users (subscribers or other service providers) directly face. In accordance with the general principles of LLA, information from the NML level is used at this level, but direct control of routers, switches, connections, etc. is no longer possible here. Here are some functions related to service management: quality control of service (QoS) and fulfillment of terms of service contracts (SLA - Service Level Agreement), management of registration records and service subscribers, adding or deleting users, assigning addresses, billing, interacting with other management systems providers and organizations (via xinterface).

The Business Management Layer (BML) considers the communications network from the point of view of the general business objectives of the operating company. It relates to strategic and tactical management, and not operational, like other levels of LLA. Here we are talking about network design and planning of its development, taking into account business objectives, budgeting, organization of external contacts, etc.

Thus, LLA levels define the functional hierarchy of network management procedures without physical segmentation of administrative software. The reason for the emergence of this hierarchy is the need for a logical separation of the functions of controlling individual network elements from the functions belonging to their groups and network connections. It is clear that the approximation of administrative procedures to those resources, which are directed to their impact, increases management efficiency. In addition, the LLA hierarchy allows the use of open standard interfaces for organizing interaction between different levels.

Works on each of the levels in fig. 7.4 five functional areas are allocated (fig. 7.5):

• trouble-shooting;
• quality control;
• configuration management;
• security management;
• settlement management.

They define a common set of protocols and services that enable the exchange of control information when interacting between a control process and a managed resource using a common set of messages. It is defined in ITU-T recommendations:

M3200 "TMN Management Services", which, in particular, introduce the concepts of "Telecommunications Management" and "Management Area".

Specific services are defined in detail in the following M.32xx series documents:

• M.3201 (traffic management);
• M.3202 (management of alarm systems);
• M.3203 (user service management):
• M.3207.1 (management channels BI SDN; in an earlier edition - M.3205), etc.

Consider in more detail these services (Fig. 7.5).

Fig. 7.5. Classification of functions of the element management level

Quality management is designed to control and maintain the required level of the main characteristics of the network. It includes the collection, processing, recording, storage and display of statistical data on the network and its elements; identifying trends in their behavior and warning about possible violations in the work.

Troubleshooting management provides detection capabilities, the location of network faults, their registration; communicating relevant information to the attendants; issuing troubleshooting tips.

Configuration management provides inventory of network elements (their types, location, identifiers, etc.); the inclusion of elements in the work, their configuration and decommissioning; establishing and modifying physical connections between elements.

Settlement management monitors the utilization of network resources and supports the functions of charging for this use.

Security management is necessary to protect the network from unauthorized access. It may include restricting access by means of passwords, issuing alarms when attempting unauthorized access, disabling unwanted users, or even cryptographic protection of information.

In conclusion, we can say that the development of recommendations has not yet been completed. But their importance is undoubted, because they contain descriptions of efficient and systematic ways of processing the various network elements and define the specified functionality, covering the maintenance of operation and maintenance systems, and also determine the distribution of functions, providing the most cost-effective centralized maintenance.

Brief summary

• The term "maintenance, operation and administration" covers all tasks that are performed by the system to ensure continuous and efficient operation and optimal use of the installed equipment.
• Administration and operation include the following tasks: change of subscriber data, control and regulation of traffic, tariffication, maintenance of the ACS system.
• Maintenance includes the following tasks: measuring and testing subscriber lines, connecting lines and channels, repairing damage, preventing hardware, modifying and ensuring reliable software operation, and maintaining databases.
• Modern digital PBX does not require the constant presence of staff. They provide self-monitoring, an alarm system, backup and failover, as well as display or printout of information at maintenance terminals.
• Software maintenance is required to correct errors in the software or in case of deviations in the behavior of the external environment.
• For efficient operation, the following software descriptions are needed: at the specification level, at the description level of what the software consists of and how it is made.
• The human-machine language is used for administration, maintenance and operation. With its help, the staff receives information about the state of the station, the state of the transmission and reception lines of information and alarm lines.
• Subscriber and connecting lines testing device provides connection of measuring devices to the subscriber line.
• The equipment connected to the cross, consists of the following parts: the measuring part, the service part.
• Auto subscriber is designed to check the quality of the station. It establishes control connections between the test station numbers that are connected to its inputs.
• Software support for administration, maintenance and operation includes: call monitoring, cost accounting system.
• The telecommunications management network includes the maintenance of proper functioning and maintenance of telecommunications networks.
• The network management system should be adapted to work in a network containing heterogeneous equipment and providing different services.
• The network management system should ensure network reliability, fault tolerance, flexible and efficient network resource management.
• The maintenance system should be standard internationally.
• The control objects in the TMN model are: the network element - NE (Network Element) and the operation support system - OSS (Operations Support Systems).
• A network element is a hardware unit of network equipment that is managed in a TMN. Operation support system - procedures (not only automated, but also, possibly, performed manually), which are aimed at maintaining the functioning of the network.
• The information model describes: functions that are controlled and monitored in a network element, rules for creating managed objects, which are determined using the operation algorithm and files for registering events.
• The manager is a part of the control programs of the distributed process, which sends commands to perform management operations and receives notifications.
• An agent is a part of a distributed process program that directly controls the relevant managed objects.
• According to the TMN concept, it is possible to single out the elements on which the communication system is built (building blocks - building blocks): network element (NE), mediator (MD), workstation (WS), Q -adapter (at the junction points q ₃ and q ₂ ).
• The logical multi-layered architecture classifies tasks according to the complexity of the managed elements (from individual devices on the network to inter-corporate networks).