HCNet: An SDN Enabled Virtual Network Management System for Hybrid Clouds Hybrid clouds require scalable, high performance virtual networks (VN) to facilitate the resource interoperability among multiple clouds. However, current VNs in hybrid clouds face the following challenges: (1) Management complexity. The VNs in hybrid clouds need to support intercloud resource deployment with multitenancy and full address space virtualization, and therefore are complex to manage. Meanwhile, the VNs are vulnerable to failures due to their large scale. (2) Performance limitation. Hybrid clouds rely on the Internet to support intercloud data transmission. Therefore without a meticulous design, the intercloud VNs would suffer from a performance limitation introduced by the Internet, e.g., the intercloud bandwidth provided by the Internet is much lower and more fluctuant than that of the intracloud networks. To the best of our knowledge, most existing VN solutions cannot solve both of these challenges simultaneously.In this paper we introduce HCNet, a hybrid cloud virtual network management system. HCNet makes use of Software Defined Networking (SDN) and: (1) supports multitenancy and full address space virtualization on both Layer2 and Layer3 networks through the help of its elaborated packet processing pipeline, (2) leverages a dynamic load balance policy atop multiple intercloud gateways to achieve better performance on intercloud virtual networking, (3) maintains masterslave backup relationship based on paxos protocol to deal with controller outages. The experiment results indicate that HCNet achieves significant intercloud communication performance gain with respect to packet loss. Moreover, in presence of controller failures, HCNet is able to recover in about 5 seconds.

An SDNbased Hybrid Strategy for Load Balancing in Data Center Networks th for various services. Yet todayxe2x80x99s widely used load balancing scheme, i.e., ECMP, may cause serious congestion when hash collision happens. Recent proposals either push load balancing function to a centralized controller or network edges. However, the centralized schemes are too slow for latencysensitive flows, while the distributed schemes lack the global view and usually cannot make the best choices. In this paper, based on SoftwareDefined Networking (SDN), we present a new hybrid load balancing scheme called BLEND. It promotes the cooperation among network components and takes advantage of both global view and fast endhost action. BLEND aims to improve the throughput of big flows and reduce the latency of small and medium flows. It employs a controller to assign paths to big flows to achieve high throughput. In addition, in order to provide guidance for fast distributed load balancing decisions, the controller also calculates the optimal network delay thresholds for small and medium flows, while hosts utilize these thresholds to decide whether to change the current paths. BLEND is practical and easily deployable in the current data center networks. Comprehensive experiments demonstrate that BLEND outperforms both the centralized and distributed schemes and achieves at most 40% reduction in FCT and at most 2.8 times improvement in throughput.