EPE with Segment Routing (SR)

This feature introduces a segment routing-based egress peer engineering (EPE) solution, allowing a centralized Path Computation Element (PCE) controller to program any egress peer policy at ingress border routers or at hosts within the domain. This can override network-derived best-path with a PCE-derived path. In EPE architecture, an autonomous system boundary router (AS boundary router) allocates segment IDs (SIDs) for its eBGP peers. These EPE SIDs are advertised by the AS boundary router in BGP Link State (BGP-LS) updates to the PCE. EPE SIDs have only local significance to the AS boundary router, and EBGP peers are not even aware of those SIDs. The AS boundary router allocates those EPE SIDs and programs the forwarding plane to steer traffic based on the incoming label in the packet. The AS boundary router pops the label and, based on the popped label, forwards the packet to the appropriate EBGP peer. Segment routing-based EPE defines the following SIDs: Peer Node-SID, Peer Adj-SID, and Peer Set-SID.