An Efficient and Accurate Link Latency Monitoring Method for Low-Latency Software-Defined Networks

This paper proposes a novel latency monitoring method for software-defined networks (SDNs) called LLDP-looping, which uses LLDP packets injected repeatedly in the control plane to determine latency between switches. It provides accurate and continuous latency monitoring without involving any dedicated network infrastructure, while avoiding potential measurement failures that can occur in the existing method of timestamping data packets as probe packets, and overcoming the major factors that decrease the measurement accuracy in many existing methods for monitoring SDN latency. We formulate an optimization problem to enable LLDP-looping to minimize its workload on both control and data planes, and propose a novel greedy algorithm to solve this problem efficiently. Evaluations over the tree-based network topologies demonstrate that LLDP-looping can effectively minimize its overhead, and provide measurement accuracy higher than 90% against the round trip time measured by Ping over an SDN with link latency as small as 0.05 ms. The advantages of LLDP-looping can be realized with minimal modifications to SDN switches and this technique can be generalized to other networking scenarios.