Consistent updates for software-defined networks

Configuration changes are a common source of instability in networks, leading to broken connectivity, forwarding loops, and access control violations. Even when the initial and final states of the network are correct, the update process often steps through intermediate states with incorrect behaviors. These problems have been recognized in the context of specific protocols, leading to a number of point solutions. However, a piecemeal attack on this fundamental problem, while pragmatic in the short term, is unlikely to lead to significant long-term progress.