At the heart of SDN/NFV-enabled packet optical transport network, a distributed hierarchical SDN Controller provides a reliable solution for orchestration of abstracted underlying network resources, and management of open APIs for vertical integration of applications, and includes 2 major components:
Central Controller performs automated network-wide bandwidth management, routing, policing, access control and other functions based on its global network picture, and interfaces with external applications.
Sub Controller interfaces with a group of network elements at Metro access & aggregation level including PTN, GPON, WiFi, etc., and exchanges control commands and other data with underlying network infrastructure within its management domain.