OSPF SR-TE Node and Adjacency SID

This feature introduces Segment routing support for OSPF protocol to provide basic functionality with Source Packet Routing in Networking (SPRING). 

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 like OSPF to advertise two types of network segments or tunnels: 

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

Ingress routers can steer a packet through a specified set of nodes and links by prepending the packet with an appropriate combination of node and/or adjacency SIDs.