Where is the Traffic Going? A Comparative Study of Clouds Following Different Designs

Cloud computing is critical for today's information society. In this paper, we shed light on two radically different cloud design philosophies: the
DC-cloud
built around massive data centers, and the
ISP-cloud
built upon a large ISP. With extensive measurements on Alibaba, Tencent, and CTYun, we find that both designs have strengths and weaknesses: the ISP-cloud of CTYun has less inflated paths to users within the same ISP, but its paths to external users are more inflated comparing with the DC-clouds of Alibaba and Tencent. By analyzing the clouds’ routing policies, we reveal the reasons behind the path inflations: Alibaba and Tencent adopt an
early-exit
policy to use more inflated public Internet paths as early as possible; while CTYun follows a
global and location-agnostic
policy to detour traffic to remote PoPs, leading to highly inflated paths. Based on the insights, we suggest alternative policies and averagely reduce 11.0% latency to 30.5% destinations for Alibaba, 9.8% latency to 18.6% destinations for Tencent, and 54.1% latency to external destinations for CTYun. The results suggest that both cloud designs have rooms for improvement, and an ISP-cloud has the potential to achieve a superior performance, thanks to its inherited advantages from the ISP infrastructure.