Segment Routing in Software Defined Networks: A Survey

Abstract

Segment routing (SR) has emerged as a promising source-routing methodology to overcome the challenges in the current routing schemes. It has received noticeable attention both in industry and academia, due to its flexibility, scalability, and applicability, especially in software defined networks. The emerging cloud services require strict service level agreements such as packet loss, delay, and jitter. Studies have shown that traditional network architectures lack the essential flexibility and scalability to offer these services. To combat this, a more flexible and agile routing paradigm of SR enables a source node to steer an incoming packet along a performance engineered path represented as an ordered list of instructions called segment list. This is encoded as a multiprotocol label switching label stack or an IPv6 address list in the packet header. This paper provides a comprehensive review of the novel SR technology by describing its architecture, operations, and key applications to date. SR paradigm can be effectively applied to a wide range of network applications, such as traffic engineering, network resiliency, network monitoring, and service function chaining, to achieve efficient network solutions. Furthermore, this paper identifies an interesting set of future research directions and open issues that can help realize the full potential of the emergent SR paradigm.