Content Distribution in P2P Systems

The report provides a literature review of the state-of-the-art for content distribution. The report's contributions are of threefold. First, it gives more insight into traditional Content Distribution Networks (CDN), their requirements and open issues. Second, it discusses Peer-to-Peer (P2P) systems as a cheap and scalable alternative for CDN and extracts their design challenges. Finally, it evaluates the existing P2P systems dedicated for content distribution according to the identied requirements and challenges

Leveraging P2P overlays for Large-scale and Highly Robust Content Distribution and Search

International audienceIn the last decade, there has been a tendency of shifting content distribution towards peer-to-peer (P2P) technology. The reason behind this is the self-scalability of P2P systems provided by the principles of communal collaboration and resource sharing in P2P systems. By building a P2P Content Distribution Network}(CDN), peers collaborate to distribute the content of under-provisioned websites and to serve queries for large audiences on behalf of the websites. When designing a P2P CDN, the main challenge is to actually maintain an acceptable level of performance in terms of client-perceived latency and hit ratio while minimizing the incurred overhead. This is not a straightforward endeavor given that the P2P CDN relies on autonomous and dynamic peers rather than a dedicated infrastructure. Indeed, the distribution of duties and content over peers should take into account their interests in order to give them proper incentives to cooperate. Moreover, the P2P-CDN should adapt to increasing numbers of participants and provide robust algorithms under high levels of churn because these issues have a key impact on performance. Finally, the routing of queries should aim peers close in locality and serve content from close-by providers to achieve short latencies. This paper gives an overview of our contributions in designing and maintaining a P2P CDN that tackles the issues identified above. First, we present Flower-CDN, a P2P content distribution network (CDN) that tackles some of these issues. Peers store only content of websites they are interested in and serve them to others. Furthermore, peers can find close-by content providers by a locality aware P2P directory structure. Secondly, we present a highly scalable approach of Flower-CDN called PetalUp-CDN which dynamically adjusts the directory structure in order to avoid overload situations and to keep the index information any peer must maintain at an acceptable level. Thirdly, we discuss maintenance protocols for Flower-CDN and PetalUp-CDN to cope with the worst scenarios of churn. The performance evaluation wrt. scalability and churn management shows that our generic approach enhances hit ratio by 40% and reduces response time by a factor of 12, compared to a well-known P2P-CDN

Flower-CDN: A hybrid P2P overlay for Efficient Query Processing in CDN

International audienceMany websites with a large user base, e.g., websites of non-profit 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 peer-to-peer based content-distribution network in which the users that are interested in a website support the distribution of its content. The idea is that peers keep the web-pages they retrieve and later serve them to other peers that are close to them in locality. Our architecture is a hybrid between structured and unstructured networks. When a node requests a web-page from a website for the first time, a locality-aware DHT quickly finds a peer in its neighborhood that has the web-page available. Additionally, all peers in a given region that maintain content of a particular website build an unstructured content overlay. Within a content overlay peers gossip information about their content allowing the system to maintain accurate information despite failures and churn. In our detailed performance evaluation, we compare Flower-CDN with Squirrel, which is a content distribution network that is strictly based on DHTs and not locality aware. Compared to Squirrel, Flower-CDN reduces lookup latency by a factor of 9 and the transfer distance by a factor of 2. We also show that Flower-CDN's gossiping has low overhead and can be adjusted according to hit ratio requirements and bandwidth availability

A Highly Robust P2P-CDN Under Large-Scale and Dynamic Participation

International audienceBy building a P2P Content Distribution Network (CDN), peers collaborate to distribute the content of under-provisioned websites and to serve queries for larger audiences on behalf of the websites. This can reveal very challenging, given the highly dynamic and autonomous participation of peers. Indeed, the P2P-CDN should adapt to increasing numbers of participants and provide robust algorithms under churn because these issues have a key impact on performance. Also, the distribution of tasks and content over peers should take into account their interests in order to give them proper incentives to cooperate. Finally, the routing of queries should aim peers close in locality and serve content from close-by providers to reduce network overload and achieve scalability. We have previously proposed a locality and interest-aware P2P-CDN, Flower-CDN, that lacks efficient management of robustness and scalability. In this paper, we focus on these crucial shortcomings and propose PetalUp-CDN. The performance evaluation with respect to scalability and churn shows highly significant gains

Location-Aware Index Caching and Searching for P2P Systems

International audienceUnstructured P2P networks remain widely deployed in file-sharing systems, due to their simple features. However, the P2P traffic, mainly composed of repetitive query messages, contributes the largest portion of the Internet traffic. The principal causes of this critical issue are the search inefficiency and the construction of the P2P overlay without any knowledge of the underlying topology. In order to reduce the P2P redundant traffic and to address the limitations of existing solutions, we propose a solution that performs index caching and efficient query routing while supporting keyword search. We aim at improving the probability of finding available copies of requested files by leveraging file replication. In addition, our scheme tries to direct queries to close results, by using topological information in terms of file physical distribution. We believe that the traffic can be reduced and the user experience ameliorated in terms of faster downloads, with minimum overhead

Locaware: Index Caching in Unstructured P2P-file Sharing Systems

International audienceThough widely deployed for file-sharing, unstructured P2P systems aggressively exploit network resources as they grow in popularity. The P2P traffic is the leading consumer of bandwidth, mainly due to search inefficiency, as well as to large data transfers over long distances. This critical issue may compromise the benefits of such systems by drastically limiting their scalability. In order to reduce the P2P redundant traffic, we propose Locaware, which performs index caching while supporting keyword search. Locaware aims at reducing the network load by directing queries to available nearby results. For this purpose, Locaware leverages natural file replication and uses topological information in terms of file physical distribution

Content Distribution in P2P Systems

The report provides a literature review of the state-of-the-art for content distribution. The report's contributions are of threefold. First, it gives more insight into traditional Content Distribution Networks (CDN), their requirements and open issues. Second, it discusses Peer-to-Peer (P2P) systems as a cheap and scalable alternative for CDN and extracts their design challenges. Finally, it evaluates the existing P2P systems dedicated for content distribution according to the identied requirements and challenges

Deployment of Flower-CDN

Flower-CDN is a Peer-to-Peer Content Distribution Network (P2P CDN) that enables any under-provisionned website to distribute its content by relying on the community interested in its content. Therefore the deployment of Flower-CDN is supported by the clients that are willing to contribute in behalf of the website of their interest. This report provides the first guidelines to make Flower-CDN available for public use. We propose to implement Flower-CDN functionality as an extension for the user's web browser. As such, the user enjoys a transparent, flexible and highly configurable experience with Flower-CDN. Furthermore, we design an implementation architecture that covers security and privacy issues in a simple and practical manner

Locaware: Index Caching in Unstructured P2P-file Sharing Systems

International audienceThough widely deployed for file-sharing, unstructured P2P systems aggressively exploit network resources as they grow in popularity. The P2P traffic is the leading consumer of bandwidth, mainly due to search inefficiency, as well as to large data transfers over long distances. This critical issue may compromise the benefits of such systems by drastically limiting their scalability. In order to reduce the P2P redundant traffic, we propose Locaware, which performs index caching while supporting keyword search. Locaware aims at reducing the network load by directing queries to available nearby results. For this purpose, Locaware leverages natural file replication and uses topological information in terms of file physical distribution

Flower-CDN: A hybrid P2P overlay for Efficient Query Processing in CDN

International audienceMany websites with a large user base, e.g., websites of non-profit 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 peer-to-peer based content-distribution network in which the users that are interested in a website support the distribution of its content. The idea is that peers keep the web-pages they retrieve and later serve them to other peers that are close to them in locality. Our architecture is a hybrid between structured and unstructured networks. When a node requests a web-page from a website for the first time, a locality-aware DHT quickly finds a peer in its neighborhood that has the web-page available. Additionally, all peers in a given region that maintain content of a particular website build an unstructured content overlay. Within a content overlay peers gossip information about their content allowing the system to maintain accurate information despite failures and churn. In our detailed performance evaluation, we compare Flower-CDN with Squirrel, which is a content distribution network that is strictly based on DHTs and not locality aware. Compared to Squirrel, Flower-CDN reduces lookup latency by a factor of 9 and the transfer distance by a factor of 2. We also show that Flower-CDN's gossiping has low overhead and can be adjusted according to hit ratio requirements and bandwidth availability