The engineering cadre of enterprise and service provider organizations would find the book beneficial. Also, this book would be of good use for universities and training institutions, given that the configuration templates have been included ? impressively for both IOS as well as IOS-XR. Also, as the definitive trend towards NGNs takes shape, more and more engineers from the traditional voice-telecom domain would be looking for knowledge on IP networks and in particular QoS in IP networks....I would expect that given the topics the book addresses, the book would be relevant for several years. Given that the CRS-1 platform of Cisco is the next generation platform that is designed to last for close to a decade, it is not inconceivable that the book has relevance for that entire period. The comprehensiveness with which the topics have been covered indicates to me that this book would indeed be a definitive guide for a long time to come.