SDN-Mon: Fine-Grained Traffic Monitoring Framework in Software-Defined Networks

Fine-grained network traffic monitoring is important for efficient network management in software-defined networking (SDN). The current SDN architecture, i.e., OpenFlow, relies on counters in the flow entries of forwarding tables for such monitoring tasks. This is not efficient nor flexible since the packet-header fields that users aim for monitoring are not always the same or overlap with those in OpenFlow match fields, which is designed for forwarding as a higher priority. This inflexibility may result in unnecessary flow entries added to switches for monitoring and controller-switch monitoring-based communication overhead, which may cause the communication channel to become a bottleneck, especially when the network includes a large number of switches. We propose SDN-Mon, a SDN-based monitoring framework that decouples monitoring from existing forwarding tables, and allows more fine-grained and flexible monitoring to serve a variety of network-management applications. SDN-Mon allows the controller to define the arbitrary sets of monitoring match fields based on the requirements of controller applications to flexibly monitor traffic. In SDN-Mon, some monitoring processes are selectively delegated to SDN switches to leverage the computing processor of the switch and avoid an unnecessary overhead in the controller-switch communication for monitoring. We implemented SDN-Mon and evaluated its performance on Lagopus switch, a high-performance software switch.