Nimble: Fast and Safe Migration of Network Functions

Network function (NF) migration alongside (and possibly because of) routing policy updates is a delicate task, making it difficult to ensure that all traffic is processed by its required network functions, in order. Indeed, all previous solutions to this problem adapt routing policy only after NFs have been migrated, in a serial fashion. This paper proposes a design called Nimble for interleaving these tasks to complete both more efficiently while ensuring complete processing of traffic by the required NFs, provided that the route-update protocol enforces a specific property that we define. We demonstrate the benefits of the Nimble design using an implementation in Open vSwitch and the Ryu controller, building on both known routing update protocols and a new protocol of our design that implements specifically the needed property.