From the Foreword: "This book lays out much of what we've learned at AT&T about SDN and NFV. Some of the smartest network experts in the industry have drawn a map to help you navigate this journey. Their goal isn't to predict the future but to help you design and build a network that will be ready for whatever that future holds. Because if there's one thing the last decade has taught us, it's that network demand will always exceed expectations. This book will help you get ready." -Randall Stephenson, Chairman, CEO, and President of AT&T "Software is changing the world, and networks too. In this in-depth book, AT&T's top networking experts discuss how they're moving software-defined networking from concept to practice, and why it's a business imperative to do this rapidly." -Urs Hoelzle, SVP Cloud Infrastructure, Google "Telecom operators face a continuous challenge for more agility to serve their customers with a better customer experience and a lower cost. This book is a very inspiring and vivid testimony of the huge transformation this means, not only for the networks but for the entire companies, and how AT&T is leading it. It provides a lot of very deep insights about the technical challenges telecom engineers are facing today. Beyond AT&T, I'm sure this book will be extremely helpful to the whole industry." -Alain Maloberti, Group Chief Network Officer, Orange Labs Networks "This new book should be read by any organization faced with a future driven by a "shift to software." It is a holistic view of how AT&T has transformed its core infrastructure from hardware based to largely software based to lower costs and speed innovation. To do so, AT&T had to redefine their technology supply chain, retrain their workforce, and move toward open source user-driven innovation; all while managing one of the biggest networks in the world. It is an amazing feat that will put AT&T in a leading position for years to come." -Jim Zemlin, Executive Director, The Linux Foundation This book is based on the lessons learned from AT&T's software transformation journey starting in 2012 when rampant traffic growth necessitated a change in network architecture and design. Using new technologies such as NFV, SDN, Cloud, and Big Data, AT&T's engineers outlined and implemented a radical network transformation program that dramatically reduced capital and operating expenditures. This book describes the transformation in substantial detail. The subject matter is of great interest to telecom professionals worldwide, as well as academic researchers looking to apply the latest techniques in computer science to solving telecom's big problems around scalability, resilience, and survivability.