Contemporary ICT systems are very complex. ICT systems provide many services to its ICT dependent customers. It is rather difficult and at the same time very desirable to keep track of the operation status of distinguished ICS system components and the ICT system as a whole. The aim of this book is to bring a comprehensive overview to the problem of enterprise ICT system monitoring. There are many monitoring tools available. Most of them are suitable for monitoring only the given particular items. It is not easy to put together information collected from more monitoring tools and systems. It is difficult to learn what to monitor and how to process an enormous number of messages generated by particular monitoring tools, networking devices, servers etc. The opinions and ideas presented in this book come from many years of experience with campus/metro computer network deployment and operations.