Uncovering Deployment Gaps in Multipath Transport through Refined Analysis and Measurement Insights

Multipath transport, which simultaneously utilizes Wi-Fi and cellular interfaces, is a promising approach to meet the stringent latency and reliability demands of real-time communication (RTC) applications such as cloud gaming, conferencing, and live streaming. Motivated by prior work demonstrating Quality of Experience (QoE) gains, we developed and deployed a multipath RTC transport using adaptive duplication. However, our large-scale production deployment did not replicate the improvements observed in testbed or emulationbased evaluations, prompting a deeper investigation. To systematically identify deployment bottlenecks, we introduce a seven-layer funnel model spanning user, device, and network layers. To our knowledge, this is the first large-scale deployment study that exposes real-world limitations of multipath RTC transport. Our five-month analysis across 30+ regions in China and over 40 million sessions reveals that sessions with >80% multipath usage achieve a 37.4% reduction in stall rate and a 20.4% decrease in end-to-end (E2E) latency on average. These results show that interpreting A/B outcomes for multipath requires accounting for deployment and session-level activation conditions.