SliM: Enabling Efficient, Seamless NFV State

Instance migration and scale-in/out operations in network functions virtualization (NFV) require state transfer mechanisms, which are known to cause service degradation through increased jitter and packet loss. Techniques such as packet duplication for state synchronization mitigate this problem, however, they incur significant additional costs. In this paper, we provide a novel interface to the VNF to announce "statelets" for incoming packets, which comprise only the information in the packet which is required for a VNF's internal state change. We further propose SliM, an efficient NFV state transfer mechanism and framework. After transferring the state snapshot to the destination, SliM transfers statelets for synchronization, allowing for a significant reduction of bandwidth requirements and the impact on VNF performance. Our evaluation results show that SliM operates seamlessly at very high dataplane utilization of physical links, up to 3 times the utilization level at which existing approaches are failing due to insufficient bandwidth for state synchronization.