document: Anycast CDNS revisited Because it is an integral part of the Internet routing apparatus , and because it allows multiple instances of the same service to be `` naturally '' discovered , IP Anycast has many attractive features for any service that involve the replication of multiple instances across the Internet . While briefly considered as an enabler when content distribution networks ( CDNs ) first emerged , the use of IP Anycast was deemed infeasible in that environment . The main reasons for this decision were the lack of load awareness of IP Anycast and unwanted side effects of Internet routing changes on the IP Anycast mechanism . Prompted by recent developments in route control technology , as well as a better understanding of the behavior of IP Anycast in operational settings , we revisit this decision and propose a load-aware IP Anycast CDN architecture that addresses these concerns while benefiting from inherent IP Anycast features . Our architecture makes use of route control mechanisms to take server and network load into account to realize load-aware Anycast . We show that the resulting redirection requirements can be formulated as a Generalized Assignment Problem and present practical algorithms that address these requirements while at the same time limiting session disruptions that plague regular IP Anycast . We evaluate our algorithms through trace based simulation using traces obtained from an operation CDN network .
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