Segment Routing with IS-IS Routing Protocol
Jeff Tantsura, Igor Milojević, Stefano Previdi, Martin Horneffer, Ahmed Samir Bashandy, Rob Shakir, Clarence Filsfils, Bruno Decraene, Saku Ytti, Stephane Litkowski, Wim Henderickx · 2013
Segment Routing (SR) enables any node to select any path (explicit or derived from IGPs SPT computations) for each of its traffic classes. The path does not depend on a hop-by-hop signaling technique (neither LDP nor RSVP). It only depends on a set of that are advertised by the IS-IS routing protocol. These segments act as topological sub-paths that can be combined together to form the desired path. There are two forms of segments: node and adjacency. A node segment represents a path to a node. An adjacency segment represents a specific adjacency to a node. A node segment is typically a multi- hop path while an adjacency segment is a one-hop path. SR's control- plane can be applied to IPv6 and MPLS dataplanes. Segment Routing control-plane can be applied to the MPLS dataplane: a node segment to node N is instantiated in the MPLS dataplane as an LSP along the shortest-path (SPT) to the node. An adjacency segment is instantiated in the MPLS dataplane as a cross-connect entry pointing to a specific egress datalink. This document describes the Segment Routing functions, a set of use cases it addresses and the necessary changes that are required in the IS-IS protocol.