Decento: A New Scalable Interactive Live Streaming System via Control Plane Decentralization

Large-scale interactive live video streaming enables real-time interaction among many streamers and viewers via video and message chat, requiring dynamic adaptation to viewers’ multi-view layouts and bandwidth conditions. Existing systems rely on SFU (Selective Forwarding Unit) servers and low-latency protocols such as WebRTC, but suffer from scalability limits: centrally aggregating all viewer states to determine bitrates incurs high computation and signaling overhead, leading to control delays that degrade responsiveness at scale. To address these challenges, we present Decento, a scalable interactive streaming system based on decentralized bitrate orchestration. Instead of centralizing viewer states, Decento lets each viewer submit preferred bitrate combinations to a nearby local control node, which aggregates them and selects representative combinations using an ϵ-covering algorithm to approximate global preferences. By forwarding only compact summaries to the central unit, Decento significantly reduces global reconfiguration complexity, suppresses signaling storms, and enables faster adaptation to viewer dynamics. Integrated with SFU servers, Decento achieves sub-3-second bitrate reconfiguration time at a 10,000-user scale — over 10× faster than state-of-the-art centralized systems — while improving average QoE by 29%.