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TMN Layers

Telecommunications Management Network (TMN) is developed by the International Telecommunications Union (ITU) as an infrastructure to support management and deployment of telecommunications services. Most popular aspect of TMN is the suggested layer model. TMN layer model divides various applications used in Network Management in multiple layers. These are described in subsequent sections.

TMN Layers

The layers identified in TMN are:

• Element Management Layer
• Network Management Layer
• Service Management Layer
• Business Management Layer

Element Management Layer

Applications in this layer are referred as Element Management System (EMS) or Element Manager in short. An EMS has direct connectivity with Network Elements and it provides remote access to most of the NE controls, to EMS operator. It logs and displays all events and alarms received from managed NEs. Using an EMS, an operator can monitor and control the network element at maximum granularity. Typically, each equipment vendor provides its respective EMS to manage its network elements. There is separate EMS for each technology. For example, if a service provider uses network elements provided by Huawei as well as Ericsson for a GSM network, then there will be one EMS provided by Huawei to manage its elements and a separate EMS provided by Ericsson to manage its respective elements. In another example, if a service provider provides both 2G and 3G services, then usually, it will have separate EMSs for both the technologies, to manage their respective network elements.

Network Management Layer

Applications in this layer are referred to as Network Management System (NMS). NMS is a manager of managers. An NMS does not have direct connectivity with Network Elements, rather it is connected with multiple EMSs. NMS manages the network over a layer of abstraction. Typically, an NMS has multi-vendor and multi-technology support. That means an NMS manages EMSs from multiple vendors and there might be a single NMS to manage both 2G as well as 3G networks. Since NMS are not tightly coupled with network elements, therefore usually they are provided by third-party vendors. NMS south-bound interface is usually standardized through standard protocols and standardized data model, whereas south-bound interface of EMSs is more often found based on proprietary protocols. For example, traditionally SNMP and CORBA are famous for connectivity between NMS and EMSs. Recently SOAP has also become popular. On the other hand, MTNM (aka TMF-814) and MTOSI are popular standards that define standardized data model and set of messages for interaction between NMS and EMSs. HP OpenView, TeMIP, SMARTS, IBM Netcool are popular third-party NMS products.

Service Management Layer

Applications in this layer are often referred as service assurance application, service activation & fulfillment application and service trouble management application. These applications work on another layer of abstraction. They consider service as unit of operations, instead of network elements. First step for design of service management layer is service modeling, where all services offered by a service provider are identified along with resources that power those services. This information is captured in a service graph. Service assurance applications are designed to determine the impact of problems in resources, on each service offered by the service provider. Examples of these services are voice service, in case of wimax and data service, MMS, caller tunes in case of GSM. Since each service provider has unique set of service offerings, therefore often a service management solution is tailor-made for each service provider, utilizing available generic products and frameworks.

Business Management Layer

Applications in this layer are meant for decision support. For example a service provider will like to know which of the service offered is under-utilized and which one is over-utilized, so that decision can be taken regarding allocation of future-funds. Similarly there are applications to design service products and track their lifecycle. And Customer Relationship Management also comes under this layer.

Interface between layers

Communication is allowed only between adjacent layers and is facilitated through NM protocols. North bound interface of each layer is powered by an agent, which provides all information relevant for the next layer.

FCAPS & TMN

While FCAPS defines NM functional areas, TMN defines level of abstraction across multiple layers.

The FCAPS model and the TMN pyramid are complementary, as depicted in the figure. The functional areas are applicable to all layers. An example – an error condition on a physical port (network element layer) is a service interruption (service management layer) which is a customer problem report and possibly a discount on the next bill (business management layer).

Theory and practice

While in theory these layers are clearly divided but in practice often there are overlaps. Many times a single application is designed to perform the job of EML as well as NML. Adding SML features in EMS applications is also in trend these days.

Standards Galore

The standards that define TMN span a large number of ITU-T documents. The X.700 series of standards define the baseline CMIP/CMIS services as well as the major management functions. The X.700 series of standards were developed to support generic OSI network management services and include:

Extending this information into a framework that is useful for the TMN services, the M.3000 series of standards have been developed. The TMN M.3000 series includes the following recommendations:

Maintainer: Brij Bhushan Ravat

Category: Nm

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