This paper describes the Stanford P2P Multicast (SPPM) streaming system that employs an overlay architecture specifically designed for low delay video applications. In order to provide interactivity to the user, this system has to keep the end-to-end delay as small as possible while guaranteeing a high video quality. A set of complimentary multicast trees is maintained to efficiently relay video traffic and a Congestion-Distortion Optimized (CoDiO) scheduler prioritizes more important video packets. Local retransmission is employed to mitigate packet loss. Real-time experiments performed on the Planet-Lab show the effectiveness of the system and the benefits of a content-aware scheduler in case of congestion or node failures. 1.

This article is an editorial note submitted to CCR. It has NOT been peer reviewed. Authors take full responsibility for this article’s technical content. Comments can be posted through CCR Online. In this paper, we discuss the current situation with respect to simulation usage in P2P research, testing the available P2P simulators against a proposed set of requirements, and surveying over 280 papers to discover what simulators are already being used. We found that no simulator currently meets all our requirements, and that simulation results are generally reported in the literature in a fashion that precludes any reproduction of results. We hope that this paper will give rise to further discussion and knowledge sharing among those of the P2P and network simulation research communities, so that a simulator that meets the needs of rigorous P2P research can be developed.

In live peer-to-peer streaming, a video stream is transmitted to a large population of viewers, through the use of the uplink bandwidth of participating peers. This approach overcomes the cost of large-scale deployment of such services. An essential problem of this type of system is to limit the incurred congestion. In particular, overwhelming the uplink of some peers would create a large increase in the latency of the system and make this application less compelling. In this work we focus on limiting the congestion in a peer-to-peer network where multiple multicast trees are used to distribute video to a large set of receivers. We present the idea of congestiondistortion optimized streaming which aims at maximizing decoded video quality while limiting network congestion. We describe how this type of media scheduling maintains high video quality even for low latencies, and extend its usage to the peer-to-peer scenario. Experiments over a simulated network of 300 peers illustrate the benefits of the suggested approach. Index Terms — Video communication, distributed computing, scheduling.

Video streaming with virtual pan/tilt/zoom functionality allows the viewer to watch arbitrary regions of a high-spatial-resolution scene. In our proposed system, the user controls his region-of-interest (ROI) interactively during the streaming session. The relevant portion of the scene is rendered on his screen immediately. An additional thumbnail overview aids his navigation. We design a peer-to-peer (P2P) multicast live video streaming system to provide the control of interactive region-of-interest (IROI) to large populations of viewers while exploiting the overlap of ROIs for efficient and scalable delivery. Our P2P overlay is altered on-the-fly in a distributed manner with the changing ROIs of the peers. The main challenges for such a system are posed by the stringent latency constraint, the churn in the ROIs of peers and the limited bandwidth at the server hosting the IROI video session. Experimental results with a network simulator indicate that the delivered quality is close to that of an alternative traditional unicast client-server delivery mechanism yet requiring less uplink capacity at the server. Index Terms — peer-to-peer video streaming, interactive regionof-interest, pan/tilt/zoom 1.

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.

Abstract — Peer-to-peer (P2P) systems are becoming increasingly popular due to their ability to deliver large amounts of data at a reduced deployment cost. While P2P systems foster the development of novel media applications, they also represent an interesting alternative paradigm for media streaming applications that can benefit from the inherent self organization and resource scalability available in such environments. This paper presents an overview of application and network layer mechanisms that enable successful streaming frameworks in peer-to-peer systems. We describe media delivery architectures that can be deployed over P2P networks, in order to address the specific requirements of streaming applications. In particular, we show how video streaming applications can benefit from the diversity offered by P2P systems, and implement distributed streaming and scheduling solutions with multipath packet transmission. I.

Abstract. In this paper we evaluate the data transmission performance of a generalized multiple-tree-based overlay architecture for peer-to-peer live streaming that employs multipath transmission and forward error correction. We give mathematical models to describe the error recovery in the presence of packet losses. We evaluate the data distribution performance of the overlay, its asymptotic behavior, the stability regions for the data transmission, and analyze the system behavior around the stability threshold. We argue that the composed measure of the mean and the variance of the packet possession probability can support adaptive forward error correction. 1

Abstract — Peer-to-peer (P2P) networks represent a valuable architecture for streaming video over the Internet. In these systems, users contribute their resources to relay the media to others and no dedicated infrastructure is required. In order to ensure a low end-to-end delay, P2P overlay networks are often organized as a set of complementary multicast trees. The source of the stream multiplexes the data on top of these trees and the routing of packets is statically defined. In this scenario, the reliability of the overlay links is critical for the performance of the system since temporary link failure or network congestion can cause a significant disruption of the end-user quality. The novel Scalable Video Coding (SVC) standard enables efficient usage of the network capacity by allowing intermediate high capacity nodes in the overlay network to dynamically extract layers from the scalable bit stream to serve less capable peers. On the other hand, SVC incurs a certain loss in terms of coding efficiency with respect to H.264/AVC single-layer coding. We propose a simple model that allows to evaluate the trade-off of using a scalable codec with respect to single-layer coding, given the distribution of the receivers ’ capacities in an error-free network. We also report experimental results obtained by using SVC on top of a real-time implementation of the Stanford Peer-to-Peer Multicast (SPPM) protocol that clearly show the benefits of a prioritization mechanism to react to network congestion. I.

Traditionally, a large number of dedicated media servers have been deployed to serve a large population of viewers for a single streaming event. However, maintaining media servers is not only costly but also usually requires over-provisioning due to the difficulty of predicting the peak size of an audience. Peer-to-Peer (P2P) streaming is a new approach to overcome these difficulties inherent in server-based streaming. We have developed the Stanford Peer-to-Peer Multicast (SPPM) protocol for live multicast streaming. SPPM constructs multiple multicast trees to push media streams to the population of peers, thereby achieving low end-to-end transmission delay. The degradation of video quality due to peer churn and packet loss in the network is reduced by video-aware packet scheduling and retransmission. In this paper, we present lessons we acquired from the deployment of a commercial variant of SPPM for a large-scale streaming event which attracted more than 33,000 viewers. We collected server logs and analyzed user statistics as well as the system performance. The results show that our system can achieve low end-to-end delay of only a few seconds with an average packet loss ratio of around 1%. We also found that improving peer-to-peer connectivity can substantially enhance the aggregate uplink capacity of P2P systems. Index Terms — Peer-to-peer multicast streaming, P2P, large-scale deployment, low-latency streaming.

Abstract — We provide a generic achievability argument for incentives in gossip based p2p streaming by proving that after coupling a randomized optimistic unchoke mechanism to an incentive based gossip streaming algorithm we can (still) distribute a stream from one source to n peers in O(log n) time with high probability. We provide simulation results for a distributed incentive scheme for gossip based p2p streaming and confirm the ability to achieve a constant (per peer in time, not across peers) stream rate to peers that is needed for streaming applications. The scheme differentiates users ’ download rates based upon how much bandwidth they contribute back to the p2p system. I.