Real-time monitoring of network latency in Software Defined Networks

Latency in a network is an important parameter that can be utilized by Service providers and end users alike. Delay on a network path is often measured using end-to-end probing packets. When multiple end systems measure end-to-end latency, there are overlaps in their paths. Since end systems do not have this knowledge, it results in redundant work and network overhead. In this paper, we propose a method to measure end-to-end path latency in Software Defined Networks (SDN). This method avoids redundant work and measures latency in real-time. Our proposal is an improvement over the looping technique. We simplified the looping technique by using IP TTL as a counter. In order to avoid duplicate work, latency is measured per link and stored in the controller. End systems may register their flow labels with the SDN controller to receive latency information. For each registered flow, controller composes individual link latencies on that path to compute end-to-end latency. We also propose another approach to measure latency using queue lengths at network switches. This technique removes network overhead. In our simulations, improved looping technique is found to be giving better results with reduced computational and network overhead, while the proposed queue length technique shows comparable results.