Software-Defined Network Overlays

Software-defined networking (SDN) is a new paradigm that promises to revolutionize the operation of networks. By proposing a separation of the data-plane from the control plane and transferring all control plane operations to a centralized controller, and equipped with a global networking view, software applications can be developed to control functionalities such as routing and forwarding in all network data-path elements. This brings significant advantages such as (i) more granularity in network control, (ii) faster implementation of new services, (iii) elimination of the need for specialized middle boxes, (iv) better security control, and (v) possibility of creating easier mechanisms to test, develop, and deploy new services. However, majority of research on SDN assume full SDN deployment; i.e., all the network components should be SDN-enabled. Yet, this may not be possible in today’s networks, where legacy devices in addition to SDN-enabled devices are commonly used. In this thesis, we focus on software-defined overlay networks, which accommodate both legacy network components such as conventional switches and routers as well as SDN-enabled network components. Design and development of software-defined overlay networks have potential to lead to incremental SDN deployment, which reduces the initial deployment costs and encourages the network operators to switch to SDN. The goal of this thesis is to understand and develop software-defined overlays, particularly focusing on the question of which network components should be SDN-enabled so that the benefits of SDNs are fully exploited. Towards this goal, we first conduct a comprehensive review of SDNs. Then, we focus on software-defined overlay networks. Finally, we implement a prototype networks to compare software-defined overlays with pure SDN (where all network components are SDN-enabled), and legacy networks (where none of the network components are SDN-enabled) via experiments conducted using the Emulab networking test-bed. We observe from our experiments that software-defined overlay networks are able to exploit the full potential of SDNs, if the SDN-enabled switches are deployed by taking into account network topologies. We believe that our results would provide useful insights on the incremental deployment of SDNs on top of the existing legacy networks.