TMN provides a framework for networks that is flexible, scalable, reliable, inexpensive to run, and easy to enhance. TMN provides for more capable and efficient networks by defining standard ways of doing network-management tasks and communicating across networks. TMN allows processing to be distributed to appropriate levels for scalability, optimum performance, and communication efficiency.

TMN principles are incorporated into a telecommunications network to send and receive information and to manage its resources. A telecommunications network is comprised of switching systems, circuits, terminals, etc. In TMN terminology, these resources are referred to as network elements (NEs). TMN enables communication between operations support systems (OSS) and NEs.

Figure 1. How the TMN Fits into a Telecommunications Network

The TMN Standard

TMN is defined in the International Telecommunications Union–Telecommunications Services Sector (ITU)–T (formerly known as the Comité Consultatif Internationale de Télégraphique et Téléphonique [CCITT]) M.3000 recommendation series. When telecommunications networks implement the TMN definitions, they become interoperable, even when interacting with the networks and equipment of other telecommunications service providers. Ultimately, interoperability can be achieved across all managed networks.

TMN uses object-oriented principles and standard interfaces to define communication between management entities in a network. The standard management interface for TMN is called the Q3 interface.

TMN architecture and interfaces, defined in the ITU M.3000 recommendation series, build on existing open systems interconnection (OSI) standards. These standards include, but are not limited to:

• common management information protocol (CMIP)—defines management services exchanged between peer entities
• guideline for definition of managed objects (GDMO)—provides templates for classifying and describing managed resources
• abstract syntax notation one (ASN.1)—provides syntax rules for data types
• open systems interconnect reference model—defines the seven-layer OSI reference model

Since their publication, the TMN standards have been embraced and promulgated by other standards bodies, most notably by the Network Management Forum (NMF), Bellcore, and the European Telecommunications Standards Institute (ETSI). In general, the NMF and Bellcore efforts are directed toward accelerating implementation and providing a generic framework for establishing detailed requirements. At the same time, technology-centric forums such as the Synchronous Optical Network (SONET) Interoperability Forum (SIF) and the Asynchronous Transfer Mode Forum (ATMF) are specifying TMN-compliant management interfaces.

TMN, OSI, and Management

TMN is based on the OSI management framework and uses an object-oriented approach, with managed information in network resources modeled as attributes in managed objects. Management functions are performed by operations comprised of common management information service (CMIS) primitives.

A network's managed information, as well as the rules by which that information is presented and managed, is referred to as the management information base (MIB). Processes that manage the information are called management entities. A management entity can take on one of two possible roles: manager or agent. Manager and agent processes send and receive requests and notifications using the CMIP.

TMN: Several Viewpoints

The benefits of TMN (multivendor, interoperable, extensible, scalable, and object-oriented) are important because they allow companies to manage complex and dynamic networks and services, and they allow those same companies to continue to expand services, maintain quality, and protect legacy investments. TMN describes telecom network management from several viewpoints: a logical or business model, a functional model, and a set of standard interfaces. Each of these is critically important and interdependent.