document: Anycast-aware transport for content delivery networks Anycast-based content delivery networks ( CDNs ) have many properties that make them ideal for the large scale distribution of content on the Internet . However , because routing changes can result in a change of the endpoint that terminates the TCP session , TCP session disruption remains a concern for anycast CDNs , especially for large file downloads . In this paper we demonstrate that this problem does not require any complex solutions . In particular , we present the design of a simple , yet efficient , mechanism to handle session disruptions due to endpoint changes . With our mechanism , a client can continue the download of the content from the point at which it was before the endpoint change . Furthermore , CDN servers purge the TCP connection state quickly to handle frequent switching with low system overhead . We demonstrate experimentally the effectiveness of our proposed mechanism and show that more complex mechanisms are not required . Specifically , we find that our mechanism maintains high download throughput even with a reasonably high rate of endpoint switching , which is attractive for load balancing scenarios . Moreover , our results show that edge servers can purge TCP connection state after a single timeout-triggered retransmission without any tangible impact on ongoing connections . Besides improving server performance , this behavior improves the resiliency of the CDN to certain denial of service attacks .
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