Identifying SDN state inconsistency in OpenStack

In Software Defined Networks (SDN), users manage network services by abstracting high level service policies from lower level network functions. Edge-based SDN, which relies on end hosts to implement lower-level network functions, has been rapidly developed and widely adopted in cloud. A critical challenge in such an environment is to ensure that lower level network configurations, which are distributed in many end hosts, are in sync with high-level network service definitions, which are maintained in the central controller, as state inconsistency often arises in practice due to unreliable state dissemination, human errors, or software bugs. In this paper, we propose an approach to systematically extracting and analyzing the network states of OpenStack from both controller and end hosts, and identifying the inconsistencies between them across multiple network layers. Through extensive experiments, we demonstrate that our system can correctly identify network state inconsistencies with little system and network overhead, therefore can be adopted in large-scale production cloud to ensure healthy operations of its network services.