Practical declarative network management

We present Flow-based Management Language (FML), a declarative policy language for managing the configuration of enterprise networks. FML was designed to replace the many disparate configuration mechanisms traditionally used to enforce policies within the enterprise. These include ACLs, VLANs, NATs, policy-routing, and proprietary admission control systems. FML balances the desires to express policies naturally and enforce policies efficiently. We have implemented FML and have used it to manage multiple operational enterprise networks for over a year.