Abstract—Existing approaches to P2P streaming can be divided into two general classes: (i) tree-based approaches use pushbased content delivery over multiple tree-shaped overlays, and (ii) mesh-based approaches use swarming content delivery over a randomly connected mesh. Previous studies have often focused on a particular P2P streaming mechanism and no comparison between these two classes has been conducted. In this paper, we compare and contrast the performance of representative protocols from each class using simulations. We identify the similarities and differences between these two approaches. Furthermore, we separately examine the behavior of content delivery and overlay construction mechanisms for both approaches in static and dynamic scenarios. Our results indicate that the meshbased approach consistently exhibits a superior performance over the tree-based approach. We also show that the main factors attributing in the inferior performance of the tree-based approach are (i) the static mapping of content to a particular tree, and (ii) the placement of each peer as an internal node in one tree and as a leaf in all other trees. I.

Video-on-demand in the Internet has become an immensely popular service in recent years. But due to its high bandwidth requirements and popularity, it is also a costly service to provide. We consider the design and potential benefits of peer-assisted video-on-demand, in which participating peers assist the server in delivering VoD content. The assistance is done in such a way that it provides the same user quality experience as pure client-server distribution. We focus on the single-video approach, whereby a peer only redistributes a video that it is currently watching. Using a nine-month trace from a client-server VoD deployment for MSN Video, we assess what the 95 percentile server bandwidth costs would have been if a peer-assisted employment had been instead used. We show that peer-assistance can dramatically reduce server bandwidth costs, particularly if peers prefetch content when there is spare upload capacity in the system. We consider the impact of peer-assisted VoD on the cross-traffic among ISPs. Although this traffic is significant, if care is taken to localize the P2P traffic within the ISPs, we can eliminate the ISP cross traffic while still achieving important reductions in server bandwidth. We also develop a simple analytical model which captures many of the critical features of peer-assisted VoD, including its operational modes.

A pervasive requirement of distributed systems is to deal with churn -- change in the set of participating nodes due to joins, graceful leaves, and failures. A high churn rate can increase costs or decrease service quality. This paper studies how to reduce churn by selecting which subset of a set of available nodes to use. First,

The latest debate in P2P and overlay multicast systems is whether or not to build trees. The main argument on the anti-tree side is that tree construction is complex, and that trees are fragile. The main counter-argument is that non-tree systems have a lot of overhead. In this paper, we argue that you can have it both ways: that one can build multi-tree systems with simple and scalable algorithms, and can still yield fast convergence and robustness. This paper presents Chunkyspread, a multi-tree, heterogeneous P2P multicast algorithm based on an unstructured overlay. Through simulation, we show that Chunkyspread can control load to within a few percent of a heterogeneous target load, and how this can be traded off for improvements in latency and tit-for-tat incentives.

In order to maximize throughput in end-system multicast, it is necessary to have fine-grained control over the transmit load of each participating member. This both avoids bottlenecks where members are overloaded, and allows heterogeneous members to contribute as much transmit capacity as they are able or willing to. In this paper, we describe and simulate an unstructured endsystem multicast protocol called Chunkyspread that provides members with fine-grained control over their transmit load, scales well, has relatively low latencies, and can tolerate high membership churn. Chunkyspread is designed as a flexible framework that easily incorporates different constraints and optimizations. For instance, it is straightforward to add tit-for-tat or path disjointness as constraints to the system. This paper demonstrates the performance of Chunkyspread through extensive simulations, and provides partial validation of these simulations on Emulab. It also provides detailed comparisons with Splitstream, a structured heterogeneous end-system multicast protocol. The simulations show that Chunkyspread provides far better control over transmit load than Splitstream, while exhibiting comparable or better latency and responsiveness to churn.

Abstract — There have been tremendous efforts and many technical innovations in supporting real-time video streaming in the past two decades, but cost-effective large-scale video broadcast has remained an elusive goal. IP multicast represented the earlier attempt to tackle this problem, but failed largely due to concerns regarding scalability, deployment, and support for higher level functionality. Recently, peer-to-peer based broadcast has emerged as a promising technique, which has been shown to be cost effective and easy to deploy. This new paradigm brings a number of unique advantages such as scalability, resilience and also effectiveness in coping with dynamics and heterogeneity. While peer-to-peer applications such as file download and voice over IP have gained tremendous popularity, video broadcast is still in its early stages and its full potential remains to be seen. This article reviews the state-of-the-art of peer-to-peer Internet video broadcast technologies. We describe the basic taxonomy of peer-to-peer broadcast and summarize the major issues associated with the design of broadcast overlays. We closely examine two approaches, namely, tree-based and data-driven, and discuss their fundamental trade-off and potential for large-scale deployment. Finally, we outline the key challenges and open problems, and highlight possible avenues for future directions. I.

Abstract—We consider the design of bandwidth-demanding broadcasting applications using overlays in environments characterized by hosts with limited and asymmetric bandwidth, and significant heterogeneity in upload bandwidth. Such environments are critical to consider to extend the applicability of overlay multicast to mainstream Internet environments where insufficient bandwidth exists to support all hosts, but have not received adequate attention from the research community. We leverage the multitree framework and design heuristics to enable it to consider host contribution and operate in bandwidth-scarce environments. Our extensions seek to simultaneously achieve good utilization of system resources, performance to hosts commensurate to their contributions, and consistent performance. We have implemented the system and conducted an Internet evaluation on PlanetLab using real traces from previous operational deployments of an overlay broadcasting system. Our results indicate for these traces, our heuristics can improve the performance of high contributors by 10–240 % and facilitate equitable bandwidth distribution among hosts with similar contributions. Index Terms—Bandwidth detection, incentive, multitree, overlay multicast, NAT, saturation detection.

Fast and effective distribution of software updates (a.k.a. patches) to millions of Internet users has evolved into a critical task over the last years. In this paper, we characterize “Windows Update”, one of the largest update services in the world, with the aim to draw general guidelines on how to best design and architect a fast and effective planet-scale patch dissemination system. To this end, we analyze an extensive set of data traces collected over the period of a year, consisting of billions of queries from over 300 million computers. Based on empirical observations and analytical results, we identify interesting properties of today’s update traffic and user behavior. Building on this analysis, we consider alternative patch delivery strategies such as caching and peer-to-peer and evaluate their performance. We identify key factors that determine the effectiveness of these schemes in reducing the server workload and the network traffic, and in speeding-up the patch delivery. Most of our findings are invariant properties induced by either user behavior or architectural characteristics of today’s Internet, and thus apply to the general problem of Internet-wide dissemination of software updates. 1

We study peer-to-peer multicast streaming, where a source distributes real-time video to a large population of hosts by making use of their forwarding capacity rather than relying on dedicated media servers. Hosts which may disconnect at any time, therefore a robust control protocol is needed to maintain connectivity among peers. This work presents a new peer-to-peer multicast protocol and analyzes the gains that video coding and prioritized packet scheduling at the application layer can bring to the overall streaming performance. A rate-distortion model which predicts endto-end video quality in throughput limited environments is presented and used to determine the over-provisioning necessary to avoid self-inflicted congestion. The video stream transmitted by the source contains H.264 SP and SI frames, which are used to adaptively stop error propagation due to packet loss. Distortion-optimized retransmission requests are issued by receiving hosts to recover the most important missing packets while limiting the induced congestion. Experiments for several hundred hosts simulated in NS-2 illustrate the benefits of our system. We achieve typical end-to-end delays of 1 sec, and a stable video quality with less than 2.5 % of frames lost to playout interruptions. Categories and Subject Descriptors

It is well-known that live multimedia streaming applications operate more efficiently when organized in peer-to-peer (P2P) topologies, since peer upload capacities are utilized to support other peers, and to alleviate the load and operating costs on the streaming servers. To date, there have been a number of existing experimental proposals with respect to how such peer-to-peer topologies are organized to support live streaming sessions. However, most of the existing proposals resort to intuition and heuristics when it comes to the design of such topology construction (i.e., neighbor selection) protocols. In this paper, we investigate the scaling laws of live P2P multimedia streaming, by quantitatively studying the asymptotic effects and tradeoffs among three key parameters in P2P streaming: server bandwidth cost, the maximum number of peers that can be supported, and the maximum number of streaming hops experienced by a peer. To further generalize our studies, we do not make restrictive assumptions in our theoretical analysis of such scaling laws: both peer upload capacities and peer lifetimes in a session may come from arbitrary distributions. With the theoretical insights we have developed, we propose Affinity, a simple and realistic heuristic to demonstrate the key benefits of our theoretical analysis in dynamic P2P networks, as compared to the topology construction algorithms in existing work.