CDNs Meet CN An Empirical Study of CDN Deployments in China

Today’s content delivery networks (CDNs) use large sets of globally distributed servers, advanced routing techniques, and dynamic server selection to provide users with low delay, reliable access to Web, and streaming content. These strategies allow CDNs to extend their reach and performance into large numbers of networks around the globe. However, nearly 20% of Internet users reside in China, where local regulations and network policies make it challenging for global CDNs to serve foreign content from servers in China and limit the effectiveness of their traditional strategies for low-latency content delivery. Recently, a number of China-specific CDNs have partnered with global CDNs to provide service in the country. However, little is known about how CDNs in China are implemented, nor their impact on performance. In this paper, we are the first to investigate the impact of China’s unique policy and networking environment on CDN implementations and deployments. We find that deployments inside China exhibit different client-mapping behavior than global ones, namely, through static server selection for clients given a customer site, and through region-specific clients partitioning and mapping rather than using live network information. We also show that ignoring these properties can significantly impact server selection quality. Our results can be useful for optimization of CDNs in China.