ServeFlow: A Fast-Slow Model Architecture for Network Traffic Analysis

Network traffic analysis increasingly uses complex machine learning models as the internet consolidates and traffic gets more encrypted. However, over high-bandwidth networks, flows can easily arrive faster than model inference rates. The temporal nature of network flows limits simple scale-out approaches leveraged in other high-traffic machine learning applications. Accordingly, this paper presents ServeFlow, a solution for machine-learning model serving aimed at network traffic analysis tasks, which carefully selects the number of packets to collect and the models to apply for individual flows to achieve a balance between minimal latency, high service rate, and high accuracy. We identify that on the same task, inference time across models can differ by 1.8x - 141.3x, while the inter-packet waiting time is up to 6-8 orders of magnitude higher than the inference time! Based on these insights, we tailor a novel fast-slow model architecture for networking ML pipelines. Flows are assigned to a slower model only when the inferences from the fast model are deemed high uncertainty. ServeFlow is able to make inferences on 76.3% of flows in under 16ms, which is a speed-up of 40.5x on the median end-to-end serving latency while increasing the service rate and maintaining similar accuracy. Even with thousands of features per flow, it achieves a service rate of over 48.5k new flows per second on a 16-core CPU commodity server, which matches the order of magnitude of flow rates observed on city-level network backbones.