Towards Decentralized Fast Consistent Updates

Abstract

Updating data plane state to adapt to dynamic conditions is a fundamental network control operation. Software-Defined Networking (SDN) offers abstractions for updating network state while preserving consistency properties. However, realizing these abstractions in a purely centralized fashion is inefficient, due to the inherent delays between switches and the SDN controller, we argue for delegating the responsibility of coordinated updates to the switches. To make our case, we propose ez-Segway, a mechanism that enables decentralized network updates while preventing forwarding anomalies and avoiding link congestion. In our architecture, the controller is only responsible for computing the intended network configuration. This information is distributed to the switches, which use partial knowledge and direct message passing to efficiently schedule and implement the update. This separation of concerns has the key benefit of improving update performance as the communication and computation bottlenecks at the controller are removed. Our extensive simulations show update speedups up to a factor of 2.