PDF of this tutorialOver the last decade the telecommunications network has been in transition. The old network was primarily designed for switched-voice traffic and was relatively simple. It was based on copper loops for subscriber access and a network of telephone exchanges to process calls. This network is evolving into one designed for integrated access, transport, and switching of voice, high-speed data, and video. The network will be based on a variety of complex technologies. As a result of its complexity, each network element technology is accompanied by an EMS that harnesses the power of the technology while masking its complexity.
Figure 1 is a conceptual view of where EMSs fit in a network. Networks today are composed of a wide variety of NEs from a large number of vendors. The machine-to-machine communication protocol between the NE and its EMS varies from NE to NE and ranges from vendor-proprietary (few new NEs have proprietary interfaces) to protocols such as TL1, premise distribution system (PDS) Snyder, signaling network management protocol (SNMP), and common management information service element (CMISE). As shown in Figure 1, the NEs in the network each communicate with their respective EMS. The NE–specific EMSs communicate via either proprietary or, preferably, an open, standard, northbound interface to a higher-level NMS that provides integrated multivendor network management.
Figure 1. Position of EMSs in the Telecommunications Network
One EMS will typically be deployed for a group of elements of the same type or system of NEs, such as digital cross-connect systems (DCSs), a ring of synchronous optical network (SONET) add-drop multiplexers (ADMs), or a hybrid fiber/coax (HFC) cable-telephony system. The role of the EMS is to control and manage all aspects of the domain and to ensure maximum usage of the devices' resources. The EMS then abstracts relevant aspects of the detailed knowledge it has of the NEs into an information model that communicates this information via the northbound interface to higher-level management systems.
The EMS is a critical piece in the total telecommunications-management solution. Only the EMS is exposed to the complete management-information content of all the NEs in its domain. The EMS is the sole mediator of this information and the control of the NEs to the network management layer. Therefore, an EMS is intimately matched to a particular network-element type and must accompany the deployment of those NEs in the network in order to enable and manage the functioning of the NEs.
