A network control system for managing a plurality of switching elements that implement a plurality of logical datapath sets. The network control system includes first and second controllers for generating requests for modifications to first and second logical datapath sets. The first controller is further for determining whether to make modifications to the first logical datapath set. The second controller is further for determining whether to make modifications to the second logical datapath set. Each controller is further for receiving logical control plane data that specifies logical datapath sets and for converting the logical control plane data to physical control plane data for propagating to the switching elements.