1. A method for operating hierarchical software defined network (SDN) controllers, the method comprising: receiving, by a parent SDN controller, regional information from one or more child SDN controllers, wherein each of the one or more child SDN controllers are assigned a different region in a domain assigned to the parent SDN controller; computing cost-based parameters in accordance with the regional information; and sending, by the parent SDN controller, the cost-based parameters to the one or more child SDN controllers, wherein the cost-based parameters are configured to be used in performing distributed network resource allocation in each of the different regions of the domain.