A scalable multi-datacenter layer-2 network architecture

Cloud today is evolving towards multi-datacenter deployment, with each datacenter serving customers in different geographical areas. The independence between datacenters, however, prohibits effective inter-datacenter resource sharing and flexible management of the infrastructure. In this paper, we propose WL2, a Software-Defined Networking (SDN) solution to an Internet-scale Layer-2 network across multiple datacenters. In WL2, a logically centralized controller handles control-plane communication and configuration in each datacenter. We achieve scalability in three ways: (1) eliminating Layer-2 broadcast by rerouting control-plane traffic to the controller; (2) introducing a layered addressing scheme for aggregate Layer-2 routing; and (3) creating an overlay abstraction on top of physical topology for fast flow setup. WL2 is fault-tolerant against controller and gateway failures. We deployed and evaluated WL2 in a 2,250-VM testbed across three datacenters. The results indicate high performance and robustness of the system.