Phase 1b is to abstract service provisioning from device configurations.
Services are to be management (by external applications[1]) via northbound interfaces of (bottom-layer) SDN controller(s). Main outcome expected of phase 1b is to introduce approach allowing gradually replace different vendor-specific REST-based APIs [2] with unified vendor-neutral RESTCONF APIs.
The work started on phase 1a (migration to vendor-neutral southbound interfaces of (bottom-layer) SDN controllers) will continue as well.
Figure 5 - phase 1b: abstract service provisioning from device configurations (northbound interfaces of bottom-layer controllers)
[1] Along with internal applications of the SDN controller
[2] API – Application Programming Interface - https://en.wikipedia.org/wiki/Application_programming_interface