The BGP-LS extension to be obsoleted allows IGP (OSPF/IS-IS) link state database information to be injected into BGP. This is typically used in deployments where some external component, (like a controller or Path Computation Engine) can do centralized path computations by learning the entire IGP topology through BGP-LS. The controller can then communicate the computed paths based on the BGP-LS updates to the head end device in the network. 

Segment Routing Traffic Engineering Policy (SR TE) aka SR Policy makes use of Segment Routing (SR) to allow a headend

By default if there's a hostname configured on the switch, it is used as the IS IS hostname. It is also possible to