If the hardware goes down or when there is some malfunction with the hardware, this would in turn affect the service. This leads to the need to monitor the hardware and ensure its proper functioning in order to offer a service to a customer. This hardware being discussed is the element and an application to monitor the same constitutes the element management system. Since the element is part of a network, it is usually referred to as network element or NE. A network element is the hardware on which a process or set of processes is executed to offer a service or plurality of services to the customer. EMS is an application that manages a telecom network element. Fundamentals of EMS, NMS and OSS/BSS Most element management systems are available in the market support man- agement data collection from multiple network elements though they cannot be called a network management system. Hence an application is not necessarily a network management system just because it supports data collection from mul- tiple NEs. The functionalities offered by the systems decide whether it is a network management system (NMS) or an element management system (EMS). Let us make this point clear with an example. A topology diagram in an EMS would have the nodes configured in the element while a topology diagram in an NMS will show all the configured network elements managed by the NMS. Again a fault management window on an EMS would show only the logs and alarms generated on the network element it is managing. The functionalities like fault correlation and decision handling based on events from various NEs are shown in an NMS. The functionalities of an EMS are covered in detail in the chapters to follow. This introduction is intended to only give the reader a feel of what a network ele- ment and EMS is in telecom domain. In the sections to follow we will explore the architecture of EMS and take some sample EMS products to gain familiarity with EMS applications available in the market. 1.2 EMS in Telecom As shown in Figure 1.1, an element m