This paper introduces cloud-assisted software-defined networking (Ca-SDN), a networking paradigm for implementing flexible and highly optimized networks by combining the strengths of cloud computing and state of the art software-defined networking technologies. The basic idea is to utilize the vast resources of datacenters ("the cloud") for complex network management functionalities such as the management of network state and optimized route calculation. The software-defined network consists of standard OpenFlow switches whose flow tables are configured based on routes calculated by an external controller hosted in the datacenter. This approach promises a clear design, flexibility, scalability, high performance, ease of administration, and cost reduction.

In this paper, we present a cloud-assisted IP multicast service as a concrete example of Ca-SDN, and discuss the benefits, challenges, and research questions for implementing Ca-SDN by this example.