CoSEL: Control-plane Only Scalable Efficient and Lightweight SDN Debugger

Abstract

Network debugging has always been a challenging task primarily because the original design of the Internet architecture gave little importance to debugging and management. In addition, the Internet makes forwarding decisions in a distributed manner, which is hard to track. With the advent of Software Defined Networks (SDNs), network debugging has potentially become easier because solely the control plane makes forwarding decisions, which is often centrally located. In this paper, we propose Control-plane Only Scalable Efficient and Lightweight SDN Debugger (CoSEL), which is to the best of our knowledge the first control-plane only, network debugger for SDN. Unlike earlier proposed debuggers, which rely on information specially obtained from the data-plane or a combination of the data and control planes, CoSEL does not require the use of any additional network bandwidth for its operation and hence outperforms existing schemes in terms of scalability. In terms of completeness, however, CoSEL does not perform as well as some existing schemes, although this loss in completeness does not prevent it from capturing most of the bugs in the network, which have1 been observed to be caused mainly by the control plane. We implement CoSEL on the Floodlight controller as a network application and present results of CoSEL in action over a network emulated by mininet. However, CoSEL is controller independent and utilizes a common programming API provided by POX, NOX and OpenDaylight. In addition, the control plane debugging of CoSEL enables it to be an effective debugging tool for network applications that are built on top of controllers utilizing Northbound APIs and interacting with network by injecting rules.