Software-Defined Latency Monitoring in Data Center Networks

Data center network operators have to continually monitor path latency to quickly detect and re-route traffic away from high-delay path segments. Existing latency monitoring techniques in data centers rely on either (1) actively sending probes from end-hosts, which is restricted in some cases and can only measure end-to-end latencies, or (2) passively capturing and aggregating traffic on network devices, which requires hardware modifications. In this work, we explore another opportunity for network path latency monitoring, enabled by software-defined networking. We propose SLAM, a latency monitoring framework that dynamically sends specific probe packets to trigger control messages from the first and last switches of a path to a centralized controller. SLAM then estimates the latency distribution along a path based on the arrival timestamps of the control messages at the controller. Our experiments show that the latency distributions estimated by SLAM are sufficiently accurate to enable the detection of latency spikes and the selection of low-latency paths in a data center.