A CDN-P2P Hybrid Architecture for Cost-Effective Streaming Media DistributionA CDN-P2P Hybrid Architecture for Cost-Effective StreamingMedia DistributionDongyan Xu?, Sunil Suresh Kulkarni?, Catherine Rosenberg?, Heung-Keung Chai?Department of Computer Sciences?School of Electrical and Computer EngineeringPurdue UniversityWest Lafayette, IN 47907, USAdxucs.purdue.edu, sunilkul, cathecn.purdue.edu, heung.keung.chaiintel4AbstractTo distribute video and audio data in real-time streaming mode, two different technologies - ContentDistribution Network (CDN) and Peer-to-Peer (P2P) - have been proposed. However, both technologies havetheir own limitations: CDN servers are expensive to deploy and maintain, and consequently incur a cost formedia providers and/or clients for server capacity reservation. On the other hand, a P2P-based architecturerequires sufficient number of seed supplying peers to jumpstart the distribution process. Compared witha CDN server, a peer usually offers much lower out-bound streaming rate and hence multiple peers mustjointly stream a media data to a requesting peer. Furthermore, it is not clear how to determine how mucha peer should contribute back to the system after receiving the media data, in order to sustain the overallmedia distribution capacity.In this paper, we propose and analyze a novel hybrid architecture that integrates both CDN and P2Pbased streaming media distribution. The architecture is highly cost-effective: it significantly lowers the costof CDN capacity reservation, without compromising the media quality delivered. In particular, we proposeand compare different limited contribution policies for peers that request a media data, so that the streamingcapacity of each peer can be exploited on a fair and limited basis. We present: (1) in-depth analysis ofthe proposed architecture under different contribution policies, and (2) extensive simulation results whichvalidate the analysis. Our analytical and simulation results form a rigorous basis for the planning anddimensioning of the hybrid architecture.EDICS: 6-MMMR?Corresponding author. Address: 250 N. University Street, West Lafayette, IN 47907-2066, USA; Phone: (765)494-6182; Fax:(765)494-0739.11 IntroductionThe proliferation of high-speed, broadband networking technologies has made real-time media streaminga reality. It is increasingly feasible to distribute video and audio data in real-time streaming mode. In fact,streaming media distribution has been an intensively studied research topic in the past few years. Amongthe most established technologies is the Content Distribution Network (CDN), where a number of CDNservers are deployed at the edge of the Internet, and clients request media streaming service from theirclosest CDN servers. More recently, peer-to-peer (P2P) based media distribution architectures have quicklygained popularity, where clients store the media data after the streaming service, and act as supplying peersby streaming the media data to other requesting clients (peers). However, we argue that both CDN-basedand P2P based architectures have their advantages and disadvantages, and each architecture alone does notprovide a cost-effective and scalable solution to streaming media distribution.In a CDN architecture, a media data is first pushed to multiple CDN servers, each of which serves clientsin its designated domain(s). A CDN server has dedicated storage space and out-bound bandwidth for high-quality media streaming. However, CDN servers are expensive to deploy and maintain. The server capacity(including processing power and out-bound bandwidth) that can be allocated to the distribution of one mediafile is limited, and it incurs a non-trivial cost to the provider and/or clients of this media file. For example,users now have to pay a subscription fee to 6view streaming videos on CNN. There exist solutionsto CDN cost control, which adaptively degrade the media quality according to the rate of client requests,and therefore bounding the CDN server capacity requirement. The downside of such solutions is that theycompromise the quality of service received by individual clients.On the other hand, P2P media streaming exhibits a more de-centralized nature: After clients receive themedia data, they will act as supplying peers and stream the data to other requesting clients (Note that wewill use the terms peers and clients interchangeably for the rest of this paper). A P2P streaming sessiontakes place between peers, without involving a CDN server. Such a P2P architecture exploits the growingaggregated streaming capacity of individual supplying peers, and therefore provides a more economical wayto disseminate the media content among the peers. However, the P2P architecture has its own problems.First, it needs a s