BGP support for SR-TE

A BGP speaker supports traffic steering based on a segment routing policy at ingress routers. The controller can specify a segment routing policy consisting of multiple paths to steer labeled or IP traffic. The segment routing policy adds an ordered list of segments to the header of a packet for traffic steering. Static policies can be configured at ingress routers to allow routing of traffic even when the link to the controller fails. To enable BGP IPv4 segment routing traffic engineering (SR-TE) capability for an address family, include the segment-routing-te statement at the [edit protocols bgp family inet] hierarchy level.