Research On The Delay In Software Defined Networking

SDN is an emerging paradigm that makes it easier to flexibly manage network and finely control flow, by promoting logical centralization of network control, and introducing the ability to program the network. In consequence, SDN can be as an infrastructure technology to support the development of future networking.SDN separate the control logic from the data plane, which emerges some new features in delay. The setup time of flow entries leads to the extra delay for the first packet. Frequent interaction between the control plane and the data plane react to some influx of flow, which dramatically aggravates load on the devices, and increases the processing delay due to their limited performance. Based on above, this paper analyses the composition and effect of delay in SDN, then proposes a solution to lower delay, furthermore, designs and achieves the controller application system based on Ryu platform, at last, evaluates the effectiveness and efficiency of delay optimizing.Path pre-installing mechanism is proposed against to the effect of flow entries setup process for the first packet, it changes the way of transmission for the first packet from flow-based to label-based. When a new flow arrive in network, the first packet is marked a label that represent a certain path, and then travel through the network along the path, instead of waiting entries inserted into flow tables on the relevant switches.Active pairs discovering mechanism is designed to aim at active interaction between the controller and switches, by devolving control down to the data plane temporarily. It use SVM classification algorithm to discover active pairs according to the several features of flow between a pair of source and destination terminal, and then setup wildcard entries along path connecting them. The new data flows coming from the active pairs travel through network following the entries’ instructions or actions before timeout, instead of invoking controller. As a consequence of load relieving and resource releasing on control plane, this mechanism also improves the data forwarding ability of the switch.As a trade-off for above, re-routing mechanism is added in the app system to balancing load in network. By selecting a high available bandwidth route for a certain elephant flow, this mechanism is expected to minimize the possibility of network congestion. Further more, in order to reduce the time cost of re-routing, BIP as a heuristic routing algorithm is introduced in the mechanism, it provides a method to hierarchically abstract the network according to bandwidth resource, which reduces searching space and then promotes the performance of route searching.