Minimum Control Latency of SDN Controller Placement

SDN is known as a decoupled architecture separatingthe control and data planes. The controller is in charge ofnetwork nodes through a southbound interface. However, it iscostly to impose all controllers to control each node separately. Meanwhile, the layout of controllers affects the network's abilityto respond to network events. Therefore, the controller placementis an important problem in SDN community. When latencyand reliability metrics are both considered, there is usuallyno single best controller placement solution, but a trade-offinstead. Most of deployment schemes based on latency are mainlyfocused on transmission delay (TD) or Propagation delay (PD) atpresent. However, to our best knowledge, no existing works haveconsidered the influence of control latency on SDN controllerplacement problem while control latency makes great sense inquick response to network events. Thus, in this paper, a minimum-control-latency optimized algorithmbased on greedy controlling pattern design is proposed. Theideas and mechanisms are illustrated using the Internet2 OS3Etopology compared to average-latency-optimized placement andworst-case-optimized placement. What's more, the accuracy oflatency measurement is also a main concern in SDN research. Itis not precise enough when measuring only based on Ping results. In this paper, a novel method based on active latency measurementis also presented to obtain more accurate control latency. Extensive experiments have shown that our minimum-controllatency-optimized can improve the imbalance when partitioningSDN domains and achieve the maximum number of nodes percontroller controlled.