OASIS: Anycast for any service

Global anycast, an important building block for many distributed services, faces several challenging requirements. First, anycast response must be fast and accurate. Second, the anycast system must minimize probing to reduce the risk of abuse complaints. Third, the system must scale to many services and provide high availability. Finally, and most importantly, such a system must integrate seamlessly with unmodified client applications. In short, when a new client makes an anycast query for a service, the anycast system must ideally return an accurate reply without performing any probing at all. This paper presents OASIS, a distributed anycast system that addresses these challenges. Since OASIS is shared across many application services, it amortizes deployment and network measurement costs; yet to facilitate sharing, OASIS has to maintain network locality information in an application-independent way. OASIS achieves these goals by mapping different portions of the Internet in advance (based on IP prefixes) to the geographic coordinates of the nearest known landmark. Measurements from a preliminary deployment show that OASIS, surprisingly, provides a significant improvement in the performance that clients experience over state-of-the-art on-demand probing and coordinate systems, while incurring much less network overhead.