The migration of the TELCO networks towards Next GenerationNetworks (NGN) requires new solutions in OSS/BSS. Thestandardization bodies for New Generation Operational software andSystems (NGOSS) are currently in the process of developing anddescribing the functional requirements and implementation solutionsfor such NGOSS applications. A large number of publicly availablesoftware applications are on offer. However the providedfunctionality and applicability of such tools is not always clearespecially in the case of the development direction of Open Sourcesoftware. This book intends to give an overview on the NGOSSstandards provided by different standardization bodies. The mainfocus was to analyze, describe and to rate Open Source applicationsseen from the TELCO point of view. Analysis, evaluation and ratingof the applicability of the selected applications were performed inthe lab environment provided by T-Mobile International GmbH and byUniversity Of Applied Sciences in Cologne.