Twist: A Multi-site Transmission Solution for On-demand Video Streaming

Abstract

Video traffic has witnessed exponential growth in recent years. As the cost optimization space of Content Delivery Network (CDN) has reached a plateau, content providers are expanding their network infrastructure to accommodate this surge. To address the cost issue, content providers have turned to cost-effective Peer-to-Peer Content Delivery Network (PCDN) solutions. However, the utilization of limited-capability PCDN nodes may lead to a decline in overall streaming performance compared to powerful CDN servers. To bridge this performance gap, we present Twist. Twist is a receiver-driven multi-site transport that leverages multiple cost-effective PCDN nodes to achieve performance equivalent to traditional CDN solutions. It incorporates a joint flow control to prevent throughput drops that can occur when using multiple content sources, and a proactive retransmission algorithm to handle frequent packet loss. Our evaluations demonstrate that Twist improves download speed on PCDN nodes by 1.71x-2.09x compared to traditional PCDN streaming solutions. Furthermore, extensive A/B testing verifies that Twist enables PCDN to achieve comparable download performance and Quality of Experience (QoE) as CDN. Over three years of commercial deployment, Twist has already served over 300 million users and has handled 35% of the video traffic, resulting in substantial cost savings for a world-leading content provider.