XRON: A Hybrid Elastic Cloud Overlay Network for Video Conferencing at Planetary Scale

Quality and cost are two key considerations for video conferencing services. Service providers face a dilemma when selecting network tiers to build their infrastructure-relying on Internet links has poor quality, while using premium links brings excessive cost. We present XRON, a hybrid elastic cloud overlay network for our planetary-scale video conferencing service. XRON differs from prior overlays with two distinct features. First, XRON is hybrid, i.e., it leverages both Internet and premium links to simultaneously achieve high quality and low cost. Second, XRON is elastic, i.e., it exploits elastic cloud resources to adaptively scale its capacity based on realtime demand. The data plane of XRON combines active probing and passive tracking for scalable link state monitoring, uses asymmetric forwarding based on heterogeneous bidirectional link qualities, and quickly reacts to sudden link degradations without the control plane involvement. The control plane of XRON predicts video traffic based on application knowledge, and computes global forwarding paths and reaction plans with scalable algorithms. Large-scale deployment in DingTalk shows that XRON reduces video stall ratio and bad audio fluency by 77% and 65.2%, respectively, compared to using Internet links only, and reduces cost by 79%, compared to using premium links only.