P4Update: Fast and locally verifiable consistent network updates in the P4 data plane

Programmable networks come with the promise of logically centralized control, in order to optimize the network's routing behavior. However, until now, controllers are heavily involved in network operations to prevent inconsistencies such as blackholes, loops, and congestion. In this paper, we propose the P4Update framework, based on the network programming language P4, to shift the consistency control and most of the routing update logic out of the overloaded and slow control plane. As such P4Update avoids high and unnecessary control plane delays by mainly scheduling and offloading the update process to the data plane. P4Update returns to operating networks in a partially centralized and distributed manner - - taking the best of both centralized and distributed worlds. The main idea is to flip the problem setting and see asynchrony as an opportunity: switches inform their local neighborhood on resolved update dependencies. What's more, our mechanisms are also provably resilient against inconsistent, reordered, or conflicting concurrent updates. Unlike prior systems, P4Update enables switches to locally verify and reject inconsistent updates, and is also the first system to resolve inter-flow update dependencies purely in the data plane, significantly reducing control plane preparation time and improving its scalability. Beyond verification, we implement P4Update in a P4 software-switch-based environment. Measurements show that P4Update outperforms existing systems with respect to update speed by 28.6% to 39.1% in average.