P2P Live Video Streaming

The ever increasing demand for video content directed the focus of researchfrom traditional server-based schemes to peer-to-peer systems for videodelivery. In such systems, video data is delivered to the users by utilizing theresources of the users themselves, leading to a potentially scalable solution.Users connect to each other, forming a p2p overlay network on top of theInternet and exchange the video segments among themselves. The performanceof a p2p system is characterized by its capability to deliver the videocontent to all peers without errors and with the smallest possible delay. Thisconstitutes a challenge since peers dynamically join and leave the overlay andalso contribute different amounts of resources to the system.The contribution of this thesis lies in two areas. The first area is theperformance evaluation of the most prominent p2p streaming architectures.We study the streaming quality in multiple-tree-based systems. We derivemodels to evaluate the stability of a multiple tree overlay in dynamic scenariosand the efficiency of the data distribution over the multiple trees. Then, westudy the data propagation in mesh-based overlays. We develop a generalframework for the evaluation of forwarding algorithms in such overlays anduse this framework to evaluate the performance of four different algorithms.The second area of the thesis is a study of streaming in heterogeneous p2poverlays. The streaming quality depends on the aggregate resources that peerscontribute to the system: low average contribution leads to low streamingquality. Therefore, maintaining high streaming quality requires mechanismsthat either prohibit non-contributing peers or encourage contribution. In thisthesis we investigate both approaches. For the former, we derive a model tocapture the evolution of available capacity in an overlay and propose simpleadmission control mechanisms to avoid capacity drainage. For the latter, inour last work, we propose a novel incentive mechanism that maximizes thestreaming quality in an overlay by encouraging highly contributing peers tooffer more of their resources.QC 2010050

Live Streaming Performance of Peer-to-Peer Systems

In peer-to-peer (P2P) live streaming systems peers organize themselves in an overlay and contributewith their resources to help diffuse live content to all peers in a timely manner. The performanceof such systems is usually characterized by the delay-loss curve, which quantifies theplayback delay required for achieving a certain streaming quality, expressed as the chunk missingratio at the peers. The streaming quality is determined by the overlay construction algorithm, theforwarding algorithm, the loss process in the underlying network, the number of peers in the overlayand their bandwidth distribution, the willingness of the peers to contribute with their resourcesand the viewing behavior of the peers (churn). The overlay construction and forwarding algorithmsare inherent characteristics of a P2P protocol, while the remaining factors are artifacts of thedeployment of the P2P system over a best-effort network such as the Internet, as well as the factthat peers act as independent agents. The current thesis addresses the problem of evaluating andimproving the performance of P2P streaming protocols based on models of the network and of thepeers' behavior. The first part of the thesis is devoted to the performance evaluation of P2P overlay constructionand forwarding algorithms and offers three contributions. First, we study the efficiency of datadistribution in multiple tree-based overlays employing forward error correction. We deriveanalytical expressions for the average packet possession probability as well as its asymptoticbounds and verify our results through simulations. Second, we evaluate the performance of astreaming system in the presence of free-riders. We define two admission control policies and studythe streaming feasibility using an analytical model and via simulations. Third, we present ananalytic framework for the evaluation of forwarding algorithms in mesh-based systems. We validate itvia simulations and use it to evaluate and to compare four push-based forwarding algorithms in termsof their delay-loss curves. The second part of the thesis investigates potential improvements to the operation of P2P streamingsystems and offers three contributions in that area. First, we study the impact of selfish peerbehavior on streaming quality in overlays where a fraction of peers has limited contribution due tophysical constraints. We show that selfish peer behavior results in suboptimal streaming quality andwe propose an incentive mechanism that increases the streaming quality by using the server uploadcapacity to reward high contributing peers. Second, we study the problem of building network aware P2P streaming overlays, taking into accountrecent measurement results that indicate that the AS-level topology of the Internet is flattening.Through extensive simulations on regular and measured topologies we show that it is possible tocreate better than random overlays relying on information about the underlying topology. Finally, westudy the problem of playout adaptation in P2P streaming systems under churn. We propose andevaluate two algorithms that tune the playback delay of the peers in such a way that the streamingquality of the peers is maintained within predetermined limits. We use simulations to show thecorrectness of the proposed algorithms and the benefits from their use.QC 2012013

On the performance of error-resilient end-point-based multicast streaming

Abstract — In this paper we propose an analytical model of a resilient end-node multicast streaming architecture based on multiple minimum-depth-trees that employs path diversity and forward error correction for improved resilience to node churns and packet losses. We study the performance of the architecture in the presence of packet losses and dynamic node behavior. We show that for a given redundancy the probability that an arbitrary node possesses a packet is high as long as the loss probability in the network is below a certain threshold. After reaching the threshold the packet possession probability suddenly drops; the rate decrease gets faster as the number of nodes in the overlay grows. The value of the threshold depends on the ratio of redundancy and on the number of the distribution trees. We study the overlay structure in the presence of node dynamics and conclude that stability can be achieved only if the root node serves a large number of nodes simultaneously. I