The book introduces and describes the software that is used to manage modern telecom networks. Such software is encompassed by the expression 'operational support systems" or OSS. OSS software provides the data that is necessary for the day-to-day operations of a telecom network including delivery of telecom services to end-customers. In addition to providing the necessary data, OSS software is increasingly responsible for issuing commands to the network infrastructure to activate new service offerings, to activate services for new customers and to detect and correct network faults. Cost imperatives have driven increasing automation in the operation of telecom networks. The need for new revenue streams forces telecom service providers to offer increasingly complex services, especially to enterprise customers. Cost-effective provision of rich services demands a central role for software and a minimal role for human technicians. Thus, OSS software is becoming central to the service offerings of telecom companies. Therefore, it is important for telecom consultants, sales people and managers to have some understanding of OSS software that manages telecom networks on a day-to-day basis. This book targets such people. The book also targets telecom engineers who are not familiar with modern OSS software. The book is designed to give a hands-on feel for OSS software. The reader should walk away with a clear idea of what it is like to sit down in front of an OSS application and make it do something. There is a large amount of literature which describes the goals of OSS software in engineering abstractions or in marketing jargon. This book aims to give the reader a concrete understanding of OSS. The reader will come to understand that OSS software is now a very real part of modern telecom operations and should be able to talk about it as such. Among its many strengths, the biggest strength of the book is that the subject area is timely. We are entering an eraof