Some embodiments of the invention provide a novel method for interfacing between a first tuple-based controller and a second controller using a message-based protocol. The method of some embodiments identifies a set of changed tuples stored in a set of output tables, generates a set of messages based on the changed tuples, and sends the generated set of messages to a second controller. In some embodiments, the first and second controllers are parts of a network control system that manages forwarding elements to implement a logical network.