Segment Routing policy is used when Automatic Traffic Steering is required. Doesn’t matter that traffic steering in specific network slice or based on some constraints. Below is the excerpt from Segment Routing Policy for Traffic Engineering IETF draft.

Segment Routing Policy: Segment Routing (SR) allows a headend node to steer a packet flow along any path. The headend node steers a flow into an Segment Routing Policy aka SR Policy.

How to Identify SR Policy: An SR Policy is identified through the tuple . The headend is the node where the policy is instantiated/implemented. The headend is specified as an IPv4 or IPv6 address.

What is Candidate Path: An SR Policy is associated with one or more candidate paths. A candidate path can either be explicit or dynamic.

What is explicit path: An explicit candidate path is associated with a SID-List or a set of SID-Lists or loopback addresses of nodes also.

What is dynamic path: A dynamic candidate path expresses an optimization objective and a set of constraints. The headend with PCE computes the solution SID-List that solves the optimization problem.