Over the past ten years, operators have heavily invested in network infrastructure because of exploding growth in IP traffic Moreover, the lack of close interaction between applications and network infrastructure has made the situation even worse Traffic engineering solutions fell short of expectations, and as a result, network infrastructures are largely underutilizedImplementation and operational complexity have led to a surge in operating expenditures, along with greater network instabilitySegment Routing SR addresses these challenges by focusing on operational simplicity, better scale, and better application utilization of the installed infrastructure achieves this by moving state from the network to the packet header This simplifies and scales the network while putting the application in controlFor the first time in the IP industry, applications program inter domain SLA enabled policies at scale through the Data Center, the metro aggregation and the backboneSegment Routing has been designed from day one for SDN and seeks the right balance between distributed intelligence, centralized optimization, and application based policy creationMany operators across different market segments Over The Top, Hyper Scale Cloud, Service Providers, Enterprise have publicly expressed their investment into Segment Routing as the de facto SDN architectureThis book aims at sharing and explaining the technology to a broad audience Formal concepts are introduced together with the use cases that lead to their definition Doing so, the reader follows the insights and experience of the inventor of the technology and understands why it was designed this way To further enhance the practical understanding of the technology, the authors have collected opinions from many operators who worked with them during this project These insights help the reader to better understand the objective and benefits of the technology and its numerous deployment use casesThis book is also available in Kindle ebook format