Date Added: Jun 2012
Configuration changes are a common source of instability in networks, leading to outages, performance disruptions, and security vulnerabilities. Even when the initial and final configurations are correct, the update process itself often steps through intermediate configurations that exhibit incorrect behaviors. This paper introduces the notion of consistent network updates - updates that are guaranteed to preserve well-defined behaviors when transitioning between configurations. The authors identify two distinct consistency levels, per-packet and per-flow, and they present general mechanisms for implementing them in Software-Defined Networks using switch APIs like OpenFlow.