Evaluating Performance and Inefficient Routing of an Anycast CDN

2019 IEEE/ACM 27th International Symposium on Quality of Service (IWQoS)(2019)

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Anycast has been increasingly deployed for content delivery networks to map clients to their nearby replicas, which relies on the underlying routing. However, the simplicity of operation comes at cost of less precise client-mapping control. Although many works have measured anycast DNS, anycast CDNs, with different service goals and engineering, are still not fully understood. In this paper, we design novel methods and combine large-scale traceroute and HTTP measurement to evaluate the overall client-proximity and inefficient routing of the largest anycast CDN, Cloudflare. We find that 90% paths traverse only 2-4 ASes, which highlights its direct networks providers. By further identifying and characterizing direct providers at finer granularity of facilities, we quantitatively shows that Cloudflare unevenly uses few large transit providers to delivery the majority of contents. Inspired by the observations, we propose an anycast routing pathology and diagnosis methodology. Investigation reveals that few huge providers have outsized impact in that they are not only related to many inter-domain inflations, but also have path inflation inside their own networks, thus deserving priority focus when troubleshooting.
content delivery,anycast,routing,measurement
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