Scalable Video Conferencing Using SDN Principles

Video-conferencing applications face an unwavering surge in traffic, stressing their underlying infrastructure in unprecedented ways. This paper rethinks the key building block for conferencing infrastructures - selective forwarding units (SFUs). SFUs relay and adapt media streams between participants and, today, run in software on general-purpose servers. Our main insight, discerned from dissecting the operation of production SFU servers, is that SFUs largely mimic traditional packet-processing operations such as dropping and forwarding. Guided by this, we present Scallop, an SDN-inspired SFU that decouples video-conferencing applications into a hardware-based data plane for latency-sensitive and frequent media operations, and a software control plane for the (infrequent) remaining tasks, such as analyzing feedback signals and session management. Scallop is a general design that is suitable for a variety of hardware platforms, including programmable switches and SmartNICs. Our Tofino-based implementation fully supports WebRTC and delivers 7-422× improved scaling over a 32-core commodity server, while reaping performance improvements by cutting forwarding-induced latency by 26×. We also present an implementation of Scallop on the BlueField-3 SmartNIC.