Flower-CDN: a hybrid P2P overlay for efficient query processing in CDN

ABSTRACT

Many websites with a large user base, e.g., websites of nonprofit organizations, do not have the financial means to install large web-servers or use specialized content distribution networks such as Akamai. For those websites, we have developed Flower-CDN, a locality-aware P2P based content-distribution network (CDN) in which the users that are interested in a website support the distribution of its content. The idea is that peers keep the content they retrieve and later serve it to other peers that are close to them in locality. Our architecture is a hybrid between structured and unstructured networks. When a new client requests some content from a website, a locality-aware DHT quickly finds a peer in its neighborhood that has the content available. Additionally, all peers in a given locality that maintain content of a particular website build an unstructured content overlay. Within this overlay, peers gossip information about their content allowing the system to maintain accurate information despite churn. In our performance evaluation, we compare Flower-CDN with an existing P2P-CDN strictly based on DHT and not locality aware. Flower-CDN reduces lookup latency by a factor of 9 and transfer distance by a factor of 2. We also show that Flower-CDN's gossip has low overhead and can be adjusted according to hit ratio requirements and bandwidth availability.

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