Hierarchical controller clusters for interconnecting different logical domains

Some embodiments provide a novel network control system for managing a set of 5 switching elements in a network. The network control system includes a first set of network controllers for managing a first set of switching elements that enable communication between a first set of machines. The network control system includes a second set of network controllers for managing a second set of switching elements that enable communication between a second set of machines. The second set of switching elements is separate from the first set of switching 0 elements and the second set of machines is separate from the first set of machines. The network control system includes a third set of network controllers for managing the first and second sets of network controllers in order to enable communication between machines in the first set of machines and machines in the second set of machines. (1/52) / -4--, 0 -z I -: ,~ ~:o ~0 (NI -~ I ~ '/2 ~0 ~:t ~',#' (NI ~ r \ ~ - If)I