  Segment routing is heralded as important technology innovation in large
provider networks. In the domain of large telecom service providers, segment
routing has the potential to be in the same league as MPLS and IPv6 as well as
pave a way towards the successful implementation of SDNs. In this regard, this
paper is a survey on the existing segment routing work in the community. We
begin by describing how segment routing works, inclusive of the various
building blocks. The paper describes the segment routing architecture in terms
of its positioning vis-a-vis existing networking technologies, as well as the
data-plane and the control plane. Label encoding techniques that are central
towards implementing segment routing are then discussed. In order to make
segment routing relevant to the current domain of providers, we postulate
various use cases, their working and issues of interoperability. The paper also
reviews the current set of segment routing implementation cases in the
industry. Thereafter we position segment routing among the various provider
manifestations.
