Segment Routing: a Comprehensive Survey of Research Activities, Standardization Efforts and Implementation Results

Fixed and mobile telecom operators, enterprise network operators and cloud providers strive to face the challenging demands coming from the evolution of IP networks (e.g. huge bandwidth requirements, integration of billions of devices and millions of services in the cloud). Proposed in the early 2010's, the Segment Routing (SR) architecture helps facing these challenging demands and it is being adopted and deployed. The SR architecture is based on the concept of source routing and has interesting scalability properties as it dramatically reduces the amount of state information to be configured in the core nodes to support complex services. The SR architecture has been first implemented with the MPLS dataplane and then, quite recently, with the IPv6 dataplane (SRv6). In this paper we present a tutorial and a comprehensive survey on the SR technology, analyzing research activities, standardization efforts and implementation results. We start with an introduction on the motivations for Segment Routing and an overview of its evolution and standardization. Then, we provide a tutorial on the Segment Routing technology, with focus on the novel SRv6 solution. Next, we thoroughly analyze the research activities according to a taxonomy. We have identified 7 main categories during our analysis of the current state of the art: Traffic Engineering, Failure Recovery, Centrally Controlled Architectures, Path Encoding, Network Programming and Miscellaneous. We also discuss the standardization efforts, providing details on the most important documents and listing other ongoing activities along with pointers to them. Last but not least, we present the up-to-date status of SR implementation and provide references to several open source projects.