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Transparent flow migration for NFV

NFV together with SDN provides the flexibility for NFs in the way that they are deployed and managed. The flexibility enables dynamical scale in and scale out through migrating in-process flows among NFs. Due to stateful packet processing in NFs, flow migration has to guarantee loss-free and order-preserving for both flow states and packets. Existing frameworks closely coupled state transfer and packets migration, and thus fail to achieve safe and efficient migration with low overhead. This paper presents our design and implementation of a distributed flow migration framework, Transparent Flow Migration (TFM). TFM completely decouples the state transfer and packets migrations. The decoupling allows us to optimize the two processes separately and run them in parallel. TFM implements various optimizations through the TFM box, a shim layer providing transparent packet migration to NFs. Our evaluation shows that TFM guarantees loss-free and order-preserving for both scale-in and scale-out flow migration, and outperforms existing approaches with 3× smaller migration time. Besides, TFM uses small overhead and has very limited impacts on throughput of live TCP flows.