Queueless and Dropless Rate Control

Modern Internet traffic is increasingly dominated by interactive video applications (e.g. cloud gaming, conferencing, etc) that require high throughput, extremely low delay, and near-zero drop rates. Meeting these requirements is inherently challenging for such applications because video encoders often need to overshoot the target bitrates, causing transient traffic bursts. These bursts lead to inevitable delays and drops on traditional Internet bottlenecks with fixed capacities and finite physical queues. However, we observe that modern Internet bottlenecks are often artificial, where ISPs intentionally limit user's traffic to subscribed rates. Our work exploits the flexibility afforded in these artificial bottlenecks to achieve zero queuing and drops for interactive applications. Specifically, we make a case for using traffic policers (implemented as token bucket filters) at the ISPs to enforce desired rate limits on an average. Policers can absorb traffic bursts without any queuing, but incur packet drops. Our system, QLDL, avoids packet drops by augmenting the policer and the endpoints with a light-weight explicit rate control mechanism. Our prototype evaluation using WebRTC applications shows how QLDL thus achieves zero queuing and drops, thereby improving interactive applications' QoE on all fronts: 2× higher bitrate, 2 – 3× lower frame delays, and 20× lower playback freezes, when compared to state-of-the-art baselines.