IS-IS Segment Routing(SR) Extensions

This feature adds support for segment routing for IS-IS. 

 Source packet routing or segment routing is a control-plane architecture that enables an ingress router to steer a packet through a specific set of nodes and links in the network without relying on the intermediate nodes in the network to determine the actual path it should take. In this context, the term "source" means "the point at which the explicit route is imposed." 

 Essentially, segment routing engages IGPs such as IS-IS and OSPF for advertising the following two types of network segments or tunnels: 

•  Strict forwarded single-hop tunnels that carry packets over a specific link between two nodes, irrespective of the link cost, referred to as adjacency segments. 
•  Multihop tunnels that use shortest path links between two specific nodes, referred to as node segments.