K AND TROUBLE MANAGEMENT As mentioned, SLAs, beyond QoS, are tied to the overall performance of an IIC's network. With IICs under the customer-service microscope, network and trouble management have grown in importance. Network and trouble Chapter 2 - A Detailed Look at OSS management systems have almost always been key parts of the OSS spectrum. They, like most other OSSs, have also become more complex and functional as a result of new network and software technologies. A general shift from a network-centric focus to a customer-centric focus among IICs also drives advances in network and trouble management systems and techniques. Network Management Systems (NMSs) Early network management systems (NMSs) did little more than report failures and other alarms occurring in the network. This reporting was done with little intelligence and required engineers to diagnose problems as multiple alarms occurred simultaneously. Current network management systems offer a much higher level of intelligence, offering greater reporting capability, predictive analysis functions and alarm correlation. They are most recognizable because of the impressive photos often taken inside network operations centers (NOCs) showing monstrous wall displays with detailed network maps and fluctuating statistical charts. Network elements, as mentioned earlier, carry more software intelligence than ever before. Much of that intelligence is designed to allow an element to take its own temperature. Elements not only alarm when they fail, they will alarm, for example, when traffic approaches certain volume thresholds or when minor faults occur that do not immediately affect performance. The long and short of it is that element alarms can bombard a network operations center (NOC) beyond human capacity to sort through all the noise. Network management systems filter, prioritize and correlate these alarms. Alarm correlation is an automated diagnostic process in which a network management system identifies related alarms and determines their root cause. I