In this section, you learn about the layers of management functions that must exist in an OSS. Network management is defined as a collective set of management functions that can be applied to a network, such as an MSPP interoffice (IOF) ring. These functions are commonly referred to as FCAPS:
These functions exist as part of the telecommunications management network (TMN) framework. The TMN layers are the framework that defines how management is logically separated in an OSS. Developed within the International Telecommunications Union (ITU), the TMN framework breaks down the management functions into different layers that represent a hierarchical structure. Figure 15-1 shows the TMN framework. Figure 15-1. TMN Framework
The TMN framework has four layers:
It is important to realize that, in many implementations of the Telecommunications Management Network (TMN) framework, management data might not be passed from a layer to the layer directly above it in all cases. Management data might pass from one layer to any layer above it, or to another system within the same layer, if required. For example, an EMS that supports EML functions might pass MSPP alarms data to a customer network management application residing at the SML. Each service provider or large enterprise that deploys its own OSS defines where the TMN functions will reside, keeping in mind the importance of not duplicating functionality. Duplication increases the complexity and cost of integrating different OSS components. Furthermore, in certain OSS deployments, an application might support functions that span multiple layers of the TMN model. For example, an EMS might support both EML and NML functions within the EMS system. This EMS might support the correlation and aggregation of statistics collected from the MSPP network, or it might not provide this correlation and might leave this function for a NMS. CTM can manage individual 15454s in an interoffice facility (IOF) ring, for example, but it can also provision and maintain end-to-end circuits traversing one or more 15454 rings. |