1. A non-transitory machine readable medium storing a program which when executed by at least one processing unit manages a plurality managed forwarding elements that forward data through a network, the program comprising sets of instructions for: receiving user inputs that define forwarding performance constraints of a set of managed forwarding elements; and based on the inputs, generating a set of universal flow entries for configuring the set of managed forwarding elements to apply the forwarding performance constraints to data traffic that the managed forwarding elements forward, the set of universal flow entries for subsequent conversion into a set of customized flow entries for the managed forwarding elements.