A Survey and Synthesis of User Behavior Measurements in P2P Streaming Systems
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paper_title: A Comparison of Resilient Overlay Multicast Approaches

paper_content:

Overlay-based multicast has been proposed as a key alternative for large-scale group communication. There is ample motivation for such an approach, as it delivers the scalability advantages of multicast while avoiding the deployment issues of a network-level solution. As multicast functionality is pushed to autonomous, unpredictable end systems, however, significant performance loss can result from their higher degree of transiency when compared to routers. Consequently, a number of techniques have recently been proposed to improve overlays' resilience by exploiting path diversity and minimizing node dependencies. Delivering high application performance at relatively low costs and under high degree of transiency has proven to be a difficult task. Each of the proposed resilient techniques comes with a different trade-off in terms of delivery ratio, end-to-end latency and additional network traffic. In this paper, we review some of these approaches and evaluate their effectiveness by contrasting the performance and associated cost of representative protocols through simulation and wide area experimentation.
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paper_title: Peer-to-Peer Media Streaming Application Survey

paper_content:

Up to now, the Internet has been growing both in size and technologically. It is also not uncommon to find many types of media within a single web-page such as 3D animations, sound, video clips, online radio and TV services. Streaming is the technology which enables this, by viewing a media while downloading it. An important amount of research has been achieved to improve this bandwidth sensitive technology. Peer-To-Peer (P2P) network is at the moment one of the most effective solution to distribute streaming data within a large scale overlay, involving potentially thousands of nodes. This paper presents a survey on existing P2P media streaming systems. Our main goal is to study different P2P media streaming applications, state their results and present our analysis of each system.
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paper_title: Opportunities and Challenges of Peer-to-Peer Internet Video Broadcast

paper_content:

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. Internet protocol (IP) multicast represented an 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 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 paper 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 - tree-based and data-driven - and discuss their fundamental tradeoff and potential for large-scale deployment. Lastly, we outline the key challenges and open problems and highlight possible avenues for future directions.
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paper_title: A Review of Resilient Approaches to Peer-to-Peer Overlay Multicast for Media Streaming

paper_content:

The success of peer-to-peer overlay multicast for media streaming depends on their scalability. However, as multicast functionality is pushed to autonomous, unpredictable end systems, significant performance loss can be resulted from their higher degree of churn when compared to routers. Data distribution path over an overlay consisting of unreliable peers is inherently subject to disturbances. Resilience is thus inevitably a key requirement to peer-to-peer streaming architectures. Currently, a number of techniques have been proposed to improve overlays resilience by exploiting path diversity to minimize nodes dependencies and data redundancy. In this article, we present a survey of the media distribution resilient approaches proposed in literature. We classify them based on overlay topology design and error-resilient control approaches, illustrating with some representative protocols. And to achieve better performance in P2P video streaming systems, multiple-tree or mesh-based overlay topologies combining with error-resilient transport is essential.
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paper_title: Opportunities and Challenges of Peer-to-Peer Internet Video Broadcast

paper_content:

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. Internet protocol (IP) multicast represented an 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 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 paper 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 - tree-based and data-driven - and discuss their fundamental tradeoff and potential for large-scale deployment. Lastly, we outline the key challenges and open problems and highlight possible avenues for future directions.
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paper_title: On next-generation telco-managed P2P TV architectures

paper_content:

In recent years, Telcos worldwide have deployed IPTV networks to offer cable TV-like services over the IP backbones. Such walled garden IPTV networks are provisioned to guarantee the quality of service, fast channel switching, and user experience expected by TV viewers. A common key design element of these networks is the use of IP multicast within a single network domain to broadcast several hundreds of TV channels to millions of receivers. However, as the amount of content and channels increase and users demand more interactive and asynchronous viewing, current IPTV architectures are showing clear limitations. In this paper, we study next-generation Telco-managed IPTV architectures, where P2P distributed systems are integrated in Telco's TV set-top boxes or home gateways. We explore how P2P can complement existing Telco-managed IPTV architectures to support advanced rewind functionalities and whether P2P can substitute IP multicast solutions towards supporting a potentially unlimited number of live channels. To this extent, we analyze the TV viewing behavior of a quarter million users using real traces from one of the largest Telco-managed IPTV networks in the world and show the synergistic strengths and the potential for various P2P IPTV combined architectures.
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paper_title: End-to-end arguments in system design

paper_content:

This paper presents a design principle that helps guide placement of functions among the modules of a distributed computer system. The principle, called the end-to-end argument, suggests that functions placed at low levels of a system may be redundant or of little value when compared with the cost of providing them at that low level. Examples discussed in the paper include bit error recovery, security using encryption, duplicate message suppression, recovery from system crashes, and delivery acknowledgement. Low level mechanisms to support these functions are justified only as performance enhancements.
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paper_title: Deployment issues for the IP multicast service and architecture

paper_content:

IP multicast offers the scalable point-to-multipoint delivery necessary for using group communication applications on the Internet. However, the IP multicast service has seen slow commercial deployment by ISPs and carriers. The original service model was designed without a clear understanding of commercial requirements or a robust implementation strategy. The very limited number of applications and the complexity of the architectural design-which we believe is a consequence of the open service model-have deterred widespread deployment as well. We examine the issues that have limited the commercial deployment of IP multicast from the viewpoint of carriers. We analyze where the model fails and what it does not offer, and we discuss requirements for successful deployment of multicast services.
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paper_title: Multicast routing in datagram internetworks and extended LANs

paper_content:

Multicasting, the transmission of a packet to a group of hosts, is an important service for improving the efficiency and robustness of distributed systems and applications. Although multicast capability is available and widely used in local area networks, when those LANs are interconnected by store-and-forward routers, the multicast service is usually not offered across the resulting internetwork . To address this limitation, we specify extensions to two common internetwork routing algorithms—distance-vector routing and link-state routing—to support low-delay datagram multicasting beyond a single LAN. We also describe modifications to the single-spanning-tree routing algorithm commonly used by link-layer bridges, to reduce the costs of multicasting in large extended LANs. Finally, we discuss how the use of multicast scope control and hierarchical multicast routing allows the multicast service to scale up to large internetworks.
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paper_title: A survey of congestion control schemes for multicast video applications

paper_content:

Congestion control for IP multicast on the Internet has been one of the main issues that challenge a rapid deployment of IP multicast. In this article, we survey and discuss the most important congestion control schemes for multicast video applications on the Internet. We start with a discussion of the different elements of a multicast congestion control architecture. A congestion control scheme for multicast video possesses specific requirements for these elements. These requirements are discussed, along with the evaluation criteria for the performance of multicast video. We categorize the schemes we present into end-to-end schemes and router-supported schemes. We start with the end-to-end category and discuss several examples of both single-rate multicast applications and layered multicast applications. For the router-supported category, we first present single-rate schemes that utilize filtering of multicast packets by the routers. Next we discuss receiver-based layered schemes that rely on routers group/flow control of multicast sessions. We evaluate a number of schemes that belong to each of the two categories.
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paper_title: A Survey on Peer-to-Peer Video Streaming Systems

paper_content:

Video-over-IP applications have recently attracted a large number of users on the Internet. Traditional client-server based video streaming solutions incur expensive bandwidth provision cost on the server. Peer-to-Peer (P2P) networking is a new paradigm to build distributed network applications. Recently, several P2P streaming systems have been deployed to provide live and on-demand video streaming services on the Internet at low server cost. In this paper, we provide a survey on the existing P2P solutions for live and on-demand video streaming. Representative P2P streaming systems, including tree, multi-tree and mesh based systems are introduced. We describe the challenges and solutions of providing live and on-demand video streaming in P2P environment. Open research issues on P2P video streaming are also discussed.
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paper_title: Inter-Overlay Cooperation in High-Bandwidth Overlay Multicast

paper_content:

The cooperation of end users can be exploited to boost the performance of high-bandwidth multicast. While intra-overlay cooperation, the mechanism for cooperation within a single overlay (multicast group), has been extensively studied, little attention has been paid to inter-overlay cooperation. In this paper we explore the possibility and effects of cooperation among co-existing heterogeneous overlays in the context of live media streaming, where bandwidth is the bottleneck resource. To motivate such a kind of cooperation, we design a reputation-based incentive mechanism that differentiates user' streaming qualities based on the amount of data actually forwarded by individual users. This not only stimulates users to contribute as much forwarding bandwidth as possible, but also motivates those with spare bandwidths in resource-rich overlays to find downstream users in external, often resource-poor, overlays so as to accumulate more reputation scores. Under this mechanism, an adaptive bandwidth exporting/reclaiming algorithm is developed which allows users to dynamically allocate bandwidth according to the resource availability of multiple overlays. Simulation results are reported with enhanced system performance in terms of users' average media quality
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paper_title: Cross-channel collaborations in peer-to-peer streaming

paper_content:

Peer-to-Peer(P2P) streaming has become a very popular technique to realize live media broadcast over the Internet. Most previous research of P2P streaming focuses on the delivery of a single media stream (called a channel). The widely deployed implementations, however, all concurrently offer multiple channels through their P2P networks. This paper investigates the overlay organization for multi-channel P2P streaming systems through modeling and simulations. In particular, this paper examines the potential collaborations among nodes across multiple channels. Our investigation shows that collaboration among nodes across different channels can improve the overall performance of the multi-channel P2P streaming system. However, the collaboration strategies need to be carefully selected. Simple collaboration strategies, such as treating collaborative nodes (those "borrowed" from other channels) the same as a channel's native nodes (those playing the channel), tend to have marginal or even negative effects on the whole system performance. This result is contrary to common impression - the larger population the better performance of P2P system - and we found that this is caused by the differences between P2P streaming and traditional P2P file-sharing systems. Furthermore, this paper proposes a set of simple strategies that controls the upload-download ratio of collaborative nodes. We showed that this set of strategies produces a much better collaboration result for multi-channel P2P streaming systems. Although only a preliminary study, we believe the results will promote further investigation on the topic of multi-channel P2P streaming.
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paper_title: Optimal Delay-Reconstruction Tradeoffs in Peer-to-Peer Networks

paper_content:

We study the tradeoff between delay and partial reconstruction in peer-to-peer networks, i.e., the number of messages a peer must obtain to reconstruct a given fraction of the file. We present a coding scheme based on erasure compression and Slepian-Wolf binning, in which peers generate coded messages based on their current knowledge of the file. Assuming symmetric peers, we show that the coding scheme provides a Pareto optimal tradeoff between delay and reconstruction, which we characterize. In the process of proving the result, we establish an improved outer bound on the rate region of the general multi-terminal source coding problem. We further show that in the case of asymmetric peers, the coding scheme is not optimal.
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paper_title: SCRIBE: A large-scale and decentralized application-level multicast infrastructure

paper_content:

This paper presents Scribe, a scalable application-level multicast infrastructure. Scribe supports large numbers of groups, with a potentially large number of members per group. Scribe is built on top of Pastry, a generic peer-to-peer object location and routing substrate overlayed on the Internet, and leverages Pastry's reliability, self-organization, and locality properties. Pastry is used to create and manage groups and to build efficient multicast trees for the dissemination of messages to each group. Scribe provides best-effort reliability guarantees, and we outline how an application can extend Scribe to provide stronger reliability. Simulation results, based on a realistic network topology model, show that Scribe scales across a wide range of groups and group sizes. Also, it balances the load on the nodes while achieving acceptable delay and link stress when compared with Internet protocol multicast.
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paper_title: CoolStreaming/DONet: a data-driven overlay network for peer-to-peer live media streaming

paper_content:

This paper presents DONet, a data-driven overlay network for live media streaming. The core operations in DONet are very simple: every node periodically exchanges data availability information with a set of partners, and retrieves unavailable data from one or more partners, or supplies available data to partners. We emphasize three salient features of this data-driven design: 1) easy to implement, as it does not have to construct and maintain a complex global structure; 2) efficient, as data forwarding is dynamically determined according to data availability while not restricted by specific directions; and 3) robust and resilient, as the partnerships enable adaptive and quick switching among multi-suppliers. We show through analysis that DONet is scalable with bounded delay. We also address a set of practical challenges for realizing DONet, and propose an efficient member and partnership management algorithm, together with an intelligent scheduling algorithm that achieves real-time and continuous distribution of streaming contents. We have extensively evaluated the performance of DONet over the PlanetLab. Our experiments, involving almost all the active PlanetLab nodes, demonstrate that DONet achieves quite good streaming quality even under formidable network conditions. Moreover, its control overhead and transmission delay are both kept at low levels. An Internet-based DONet implementation, called CoolStreaming v.0.9, was released on May 30, 2004, which has attracted over 30000 distinct users with more than 4000 simultaneously being online at some peak times. We discuss the key issues toward designing CoolStreaming in this paper, and present several interesting observations from these large-scale tests; in particular, the larger the overlay size, the better the streaming quality it can deliver.
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paper_title: PRIME: peer-to-peer receiver-driven mesh-based streaming

paper_content:

The success of file swarming mechanisms such as BitTorrent has motivated a new approach for scalable streaming of live content that we call mesh-based Peer-to-Peer (P2P) streaming. In this approach, participating end-systems (or peers) form a randomly connected mesh and incorporate swarming content delivery to stream live content. Despite the growing popularity of this approach, neither the fundamental design tradeoffs nor the basic performance bottlenecks in mesh-based P2P streaming are well understood. In this paper, we follow a performance-driven approach to design PRIME, a scalable mesh-based P2P streaming mechanism for live content. The main design goal of PRIME is to minimize two performance bottlenecks, namely bandwidth bottleneck and content bottleneck. We show that the global pattern of delivery for each segment of live content should consist of a diffusion phase which is followed by a swarming phase. This leads to effective utilization of available resources to accommodate scalability and also minimizes content bottleneck. Using packet level simulations, we carefully examine the impact of overlay connectivity, packet scheduling scheme at individual peers and source behavior on the overall performance of the system. Our results reveal fundamental design tradeoffs of mesh-based P2P streaming for live content.
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paper_title: Chainsaw : Eliminating Trees from Overlay Multicast

paper_content:

In this paper, we present Chainsaw, a p2p overlay multicast system that completely eliminates trees. Peers are notified of new packets by their neighbors and must explicitly request a packet from a neighbor in order to receive it. This way, duplicate data can be eliminated and a peer can ensure it receives all packets. We show with simulations that Chainsaw has a short startup time, good resilience to catastrophic failure and essentially no packet loss. We support this argument with real-world experiments on Planetlab and compare Chainsaw to Bullet and Splitstream using MACEDON.
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paper_title: A Comparison of Resilient Overlay Multicast Approaches

paper_content:

Overlay-based multicast has been proposed as a key alternative for large-scale group communication. There is ample motivation for such an approach, as it delivers the scalability advantages of multicast while avoiding the deployment issues of a network-level solution. As multicast functionality is pushed to autonomous, unpredictable end systems, however, significant performance loss can result from their higher degree of transiency when compared to routers. Consequently, a number of techniques have recently been proposed to improve overlays' resilience by exploiting path diversity and minimizing node dependencies. Delivering high application performance at relatively low costs and under high degree of transiency has proven to be a difficult task. Each of the proposed resilient techniques comes with a different trade-off in terms of delivery ratio, end-to-end latency and additional network traffic. In this paper, we review some of these approaches and evaluate their effectiveness by contrasting the performance and associated cost of representative protocols through simulation and wide area experimentation.
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paper_title: Exploring content delivery networking

paper_content:

One of the hot topics in the networking industry is content delivery networking. Unfortunately, if you ask five people for a definition of a content delivery network (CDN), you will probably get five different answers. We hope to clear up some of the confusion surrounding CDNs, discuss how typical enterprise and service provider networks are likely to use them, and describe the business drivers that will fuel their growth in the coming years.
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paper_title: From Epidemics to Distributed Computing

paper_content:

Abstract—Epidemic algorithms have been recently rec-ognized as robust and scalable means to disseminate infor-mation in large-scale settings. Information is disseminatedreliably in a distributed system the same way an epidemicwould be propagated throughout a group of individuals:each process of the system chooses random peers to whomit relays the information it has received. The underlyingpeer-to-peer communication paradigm is the key to thescalability of the dissemination scheme.Epidemic algorithms have been studied theoretically andtheir analysis is built on sound mathematical foundations.Although promising, their general applicability to largescale distributed systems has yet to go through addressingmany issues. These constitute an exciting research agenda.Index Terms—Scalability, peer-to-peer, epidemics, in-formation dissemination, random graphs, probabilisticreliability. T HE SERVER IS EVERYWHERE The traditional client-server computing model is notadequate to address reliability and scalability properties.Even when servers are replicated for fault-tolerance, thesynchronisation mechanism needed to preserve replicaconsistency is a major source of overhead.The peer-to-peer computing model represents a rad-ically different and a plausible alternative for manylarge scale applications in Internet-wide settings. In thismodel, resources are shared between end-user processesthemselves in a peer style, meaning that every such pro-cess potentially acts both as a client and a server. Centralpoints of failures disappear as well as the associatedperformance bottlenecks. Scalability is achieved becausethe load, whether it consists in forwarding messages orstoring data for example, is balanced between all pro-cesses of the system. In addition, each process requiresonly local knowledge of the state of the system.Application-level multicast is one of the distributedapplications which may beneﬁt from such a communi-cation paradigm to scale to large systems. The designof scalable peer-to-peer application-level multicast pro-tocols is not straightforward and represents an active areaof research. This is one of the challenges that epidemicinformation dissemination algorithms take up [2].E
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paper_title: SplitStream: high-bandwidth multicast in cooperative environments

paper_content:

In tree-based multicast systems, a relatively small number of interior nodes carry the load of forwarding multicast messages. This works well when the interior nodes are highly-available, dedicated infrastructure routers but it poses a problem for application-level multicast in peer-to-peer systems. SplitStream addresses this problem by striping the content across a forest of interior-node-disjoint multicast trees that distributes the forwarding load among all participating peers. For example, it is possible to construct efficient SplitStream forests in which each peer contributes only as much forwarding bandwidth as it receives. Furthermore, with appropriate content encodings, SplitStream is highly robust to failures because a node failure causes the loss of a single stripe on average. We present the design and implementation of SplitStream and show experimental results obtained on an Internet testbed and via large-scale network simulation. The results show that SplitStream distributes the forwarding load among all peers and can accommodate peers with different bandwidth capacities while imposing low overhead for forest construction and maintenance.
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paper_title: Scalable application layer multicast

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We describe a new scalable application-layer multicast protocol, specifically designed for low-bandwidth, data streaming applications with large receiver sets. Our scheme is based upon a hierarchical clustering of the application-layer multicast peers and can support a number of different data delivery trees with desirable properties.We present extensive simulations of both our protocol and the Narada application-layer multicast protocol over Internet-like topologies. Our results show that for groups of size 32 or more, our protocol has lower link stress (by about 25%), improved or similar end-to-end latencies and similar failure recovery properties. More importantly, it is able to achieve these results by using orders of magnitude lower control traffic.Finally, we present results from our wide-area testbed in which we experimented with 32-100 member groups distributed over 8 different sites. In our experiments, average group members established and maintained low-latency paths and incurred a maximum packet loss rate of less than 1% as members randomly joined and left the multicast group. The average control overhead during our experiments was less than 1 Kbps for groups of size 100.
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paper_title: IP anycast point-to-(any) point communication

paper_content:

The Internet supports three communication paradigms. The first, unicast, is the point-to-point flow of packets between a single source (client) and destination (server) host. Web browsing and file Me transfer are unicast applications. The next, multicast, is the point-to-multipoint flow of packets between a single source host and one or more destination hosts. Broadcast-style videoconferencing, for example, employs IP multicast. Anycast is the point-to-point flow of packets between a single client and the "nearest" destination server identified by an anycast address. The idea behind anycast is that a client wants to send packets to any one of several possible servers offering a particular service or application but does not really care which one. Any number of servers can be assigned a single anycast address within an anycast group. A client sends packets to an anycast server by placing the anycast address in the packet header. Routers then attempt to deliver the packet to a server with the matching anycast address.
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paper_title: PALS: peer-to-peer adaptive layered streaming

paper_content:

This paper presents a new framework for Peer-to-Peer Adaptive Layered Streaming, called PALS. PALS is a receiver-driven approach for quality adaptive playback of layer encoded streaming media from a group of congestion controlled sender peers to a single receiver peer. Since the effective throughput from each sender is variable and not known a priori, it is challenging to coordinate delivery among active senders. In PALS, the receiver orchestrates coordinated delivery among active senders by adaptively determining: 1) a subset of senders that maximize overall throughput, 2) overall quality (i.e. number of layers) that can be delivered from these senders as well as distribution of overall throughput among active layers, and most importantly 3) required packets to be delivered by each active sender in order to effectively cope with any sudden change in throughput from individual senders. We describe PALS framework, identify key components of the framework and their interesting design challenges, present sample solution for the key components, and present our preliminary results.
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paper_title: mTreebone: A Collaborative Tree-Mesh Overlay Network for Multicast Video Streaming

paper_content:

Recently, application-layer overlay networks have been suggested as a promising solution for live video streaming over the Internet. To organize a multicast overlay, a natural structure is a tree, which, however, is known vulnerable to end-hosts dynamics. Data-driven approaches address this problem by employing a mesh structure, which enables data exchanges among multiple neighbors, and thus, greatly improves the overlay resilience. It unfortunately suffers from an efficiency-delay trade-off, because data have to be pulled from mesh neighbors by using extra notifications periodically. In this paper, we closely examine the contributions of overlay nodes, and argue that performance of a mesh overlay closely depends on a small set of stable backbone nodes. This is validated through a real trace study on PPLive, the largest commercial application-layer live streaming system to date. Motivated by this observation, we then suggest a novel collaborative tree-mesh design that leverages both mesh and tree structures. The key idea is to identify a set of stable nodes to construct a tree-based backbone, called treebone, with most of the data being pushed over this backbone. These stable nodes, together with others, are further organized through an auxiliary mesh overlay, which facilitates the treebone to accommodate node dynamics and fully exploit the available bandwidth between overlay nodes. This hybrid design, referred to as mTreebone, brings a series of unique and critical design challenges. In particular, the identification of stable nodes and seamless data delivery using both push and pull methods. In this paper, we present optimized solutions to these problems, which reconcile the two overlays under a coherent framework with controlled overhead. We evaluate mTreebone through both simulations and PlanetLab experiments. The results demonstrate the superior efficiency and robustness of this hybrid solution in both static and dynamic scenarios.
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paper_title: Enabling Adaptive Video Streaming in P2P Systems

paper_content:

Peer-to-peer (P2P) systems are becoming increasingly popular due to their ability to deliver large amounts of data at a reduced deployment cost. In addition to fostering the development of novel media applications, P2P systems 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 article 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 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 multi-path packet transmission.
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paper_title: LT codes

paper_content:

We introduce LT codes, the first rateless erasure codes that are very efficient as the data length grows.
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paper_title: Large-scale live media streaming over peer-to-peer networks through global internet

paper_content:

We describe the design and implementation of unstructured peer-to-peer networks for large-scale live media streaming through global Internet in this paper. In so called GridMedia system, we adopt gossip-based protocol to organize end nodes into an application layer overlay. Each node in GridMedia independently selects its neighbors and utilizes a novel and efficient push-pull streaming mechanism to fetch data from neighbors with low latency and little redundancy. The traditional pull mode in the unstructured overlay has inherent robustness to high churn rate which is common in peer-to-peer environment while the push mode could efficiently diminish the accumulated latency observed at end users. A practical system based on this architecture has been developed, and we evaluate its performance on PlanetLab [10] in various rigorous conditions. All the results demonstrate that the proposed push-pull method in GridMedia achieves good performance even with high group change rate and very low upload bandwidth limitation. Furthermore, this system was provided for CCTV (the largest TV station in China) to live broadcast the Gala Evening of Spring Festival 2005 over global Internet at the bit rate of 300 Kbps. It is evidenced that more than 500,000 users were attracted all over the world with the peak concurrent online users of 15,239 during the night.
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paper_title: Queuing Network Models for Multi-Channel P2P Live Streaming Systems

paper_content:

In recent years there have been several large-scale deployments of P2P live video systems. Existing and future P2P live video systems will offer a large number of channels, with users switching frequently among the channels. In this paper, we develop infinite-server queueing network models to analytically study the performance of multi-channel P2P streaming systems. Our models capture essential aspects of multi-channel video systems, including peer channel switching, peer churn, peer bandwidth heterogeneity, and Zipf-like channel popularity. We apply the queueing network models to two P2P streaming designs: the isolated channel design (ISO) and the View-Upload Decoupling (VUD) design. For both of these designs, we develop efficient algorithms to calculate critical performance measures, develop an asymptotic theory to provide closed-form results when the number of peers approaches infinity, and derive near- optimal provisioning rules for assigning peers to groups in VUD. We use the analytical results to compare VUD with ISO. We show that VUD design generally performs significantly better, particularly for systems with heterogeneous channel popularities and streaming rates.
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paper_title: Towards low-redundancy push-pull P2P live streaming

paper_content:

P2P live streaming systems are developed in two major approaches: tree-push versus mesh-pull. The hybrid push-pull streaming, as an emerging and promising approach, offers a good tradeoff between traffic overhead and system throughput. In this paper, we demonstrate that video redundancy is a large contributor of the traffic overhead in push-pull systems. To reduce the traffic overhead, we propose simple but effective sub-stream scheduling and re-scheduling mechanisms, implemented in a push-pull streaming prototype called Low-redundancy Streaming (LStreaming). To demonstrate its effectiveness on reducing the traffic overhead, we conduct both simulation and prototype experiments and compare the proposed LStreaming with random mesh-pull and GridMedia. The simulation results show that LStreaming significantly reduces the total traffic overhead, i.e., up to 33% and 37% reduction compared with mesh-pull and GridMedia in dynamic P2P environments, respectively. LStreaming also achieves the throughput, more close to the optimal value than the other two schemes, and sustains a better video playback quality. The prototype experiments show that LStreaming is practical and achieves the expected performance.
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paper_title: On large-scale peer-to-peer streaming systems with network coding

paper_content:

Live peer-to-peer (P2P) streaming has recently received much research attention, with successful commercial systems showing its viability in the Internet. Nevertheless, existing analytical studies of P2P streaming systems have failed to mathematically investigate and understand their critical properties, especially with a large scale and under extreme dynamics such as a flash crowd scenario. Even more importantly, there exists no prior analytical work that focuses on an entirely new way of designing streaming protocols, with the help of network coding. In this paper, we seek to show an in-depth analytical understanding of fundamental properties of P2P streaming systems, with a particular spotlight on the benefits of network coding. We show that, if network coding is used according to certain design principles, provably good performance can be guaranteed, with respect to high playback qualities, short initial buffering delays, resilience to peer dynamics, as well as minimal bandwidth costs on dedicated streaming servers. Our results are obtained with mathematical rigor, but without sacrificing realistic assumptions of system scale, peer dynamics, and upload capacities. For further insights, streaming systems using network coding are compared with traditional pull-based streaming in large-scale simulations, with a focus on fundamentals, rather than protocol details. The scale of our simulations throughout this paper exceeds 200,000 peers at times, which is in sharp contrast with existing empirical studies, typically with a few hundred peers involved.
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paper_title: MultiPeerCast: A Tree-Mesh-Hybrid P2P Live Streaming Scheme Design and Implementation Based on PeerCast

paper_content:

In this paper, we firstly analyze the mechanism of PeerCast as a P2P live streaming solution. An then, based on the shortcoming analysis of tree-based PeerCast, we propose a improved tree-mesh-hybrid scheme-MultiPeerCast, including Multi-thread media transmission, multiple-to-one overlay network reconstruct, optimized buffer design, media retrieving style changing from push mode to pull mode. As part of experiment work, we discuss an improved P2P live streaming prototype system implementation based on MultiPeerCast. The experiment results verify MultiPeerCast scheme is more stable and efficient than PeerCast. At last, from our research experiences and related survey, we analyze the prospective research direction and challenges in this field.
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paper_title: Multiple Description Coding: Compression Meets the Network

paper_content:

This article focuses on the compressed representations of pictures. The representation does not affect how many bits get from the Web server to the laptop, but it determines the usefulness of the bits that arrive. Many different representations are possible, and there is more involved in their choice than merely selecting a compression ratio. The techniques presented represent a single information source with several chunks of data ("descriptions") so that the source can be approximated from any subset of the chunks. By allowing image reconstruction to continue even after a packet is lost, this type of representation can prevent a Web browser from becoming dormant.
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paper_title: Network Coding Applications

paper_content:

Network coding is an elegant and novel technique introduced at the turn of the millennium to improve network throughput and performance. It is expected to be a critical technology for networks of the future. This tutorial deals with wireless and content distribution networks, considered to be the most likely applications of network coding, and it also reviews emerging applications of network coding such as network monitoring and management. Multiple unicasts, security, networks with unreliable links, and quantum networks are also addressed. The preceding companion deals with theoretical foundations of network coding.
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paper_title: Raptor codes

paper_content:

This paper exhibits a class of universal Raptor codes: for a given integer k, and any real /spl epsiv/>0, Raptor codes in this class produce a potentially infinite stream of symbols such that any subset of symbols of size k(1 + /spl epsiv/) is sufficient to recover the original k symbols, with high probability. Each output symbol is generated using O(log(1//spl epsiv/)) operations, and the original symbols are recovered from the collected ones with O(klog(1//spl epsiv/)) operations.
---
paper_title: View-Upload Decoupling: A Redesign of Multi-Channel P2P Video Systems

paper_content:

In current multi-channel live P2P video systems, there are several fundamental performance problems including exceedingly-large channel switching delays, long playback lags, and poor performance for less popular channels. These performance problems primarily stem from two intrinsic characteristics of multi-channel P2P video systems: channel churn and channel- resource imbalance. In this paper, we propose a radically different cross-channel P2P streaming framework, called view-upload decoupling (VUD). VUD strictly decouples peer downloading from uploading, bringing stability to multichannel systems and enabling cross-channel resource sharing. We propose a set of peer assignment and bandwidth allocation algorithms to properly provision bandwidth among channels, and introduce substream swarming to reduce the bandwidth overhead. We evaluate the performance of VUD via extensive simulations as well with a PlanetLab implementation. Our simulation and PlanetLab results show that VUD is resilient to channel churn, and achieves lower switching delay and better streaming quality. In particular, the streaming quality of small channels is greatly improved.
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paper_title: Redesigning multi-channel P2P live video systems with View-Upload Decoupling

paper_content:

In current multi-channel P2P live video systems, there are several fundamental performance problems including exceedingly-large channel switching delays, long playback lags, and poor performance for less popular channels. These performance problems primarily stem from two intrinsic characteristics of multi-channel P2P video systems: channel churn and channel-resource imbalance. In this paper, we propose a radically different cross-channel P2P streaming framework, called View-Upload Decoupling (VUD). VUD strictly decouples peer downloading from uploading, bringing stability to multi-channel systems and enabling cross-channel resource sharing. We propose a set of peer assignment and bandwidth allocation algorithms to properly provision bandwidth among channels, and introduce substream-swarming to reduce the bandwidth overhead. We evaluate the performance of VUD via extensive simulations as well with a PlanetLab implementation. Our simulation and PlanetLab results show that VUD is resilient to channel churn, and achieves lower switching delay and better streaming quality. In particular, the streaming quality of small channels is greatly improved.
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paper_title: Modeling and Analysis of Multichannel P2P Live Video Systems

paper_content:

In recent years, there have been several large-scale deployments of P2P live video systems. Existing and future P2P live video systems will offer a large number of channels, with users switching frequently among the channels. In this paper, we develop infinite-server queueing network models to analytically study the performance of multichannel P2P live video systems. Our models capture essential aspects of multichannel video systems, including peer channel switching, peer churn, peer bandwidth heterogeneity, and Zipf-like channel popularity. We apply the queueing network models to two P2P streaming designs: the isolated channel design (ISO) and the View-Upload Decoupling (VUD) design. For both of these designs, we develop efficient algorithms to calculate critical performance measures, develop an asymptotic theory to provide closed-form results when the number of peers approaches infinity, and derive near-optimal provisioning rules for assigning peers to groups in VUD. We use the analytical results to compare VUD with ISO. We show that VUD design generally performs significantly better, particularly for systems with heterogeneous channel popularities and streaming rates.
---
paper_title: Asymptotics for the random coupon collector problem

paper_content:

We develop techniques of computing the asymptotics of the expected number of items that one has to check in order to detect all N existing kinds, as N → ∞. The occurring frequencies of the differend kinds are random variables.
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paper_title: Coolstreaming: Design, Theory, and Practice

paper_content:

Peer-to-peer (P2P) technology has found much success in applications like file distributions and VoIP yet, its adoption in live video streaming remains as an elusive goal. Our recent success in Coolstreaming system brings promises in this direction; however, it also reveals that there exist many practical engineering problems in real live streaming systems over the Internet. Our focus in this paper is on a nonoptimal real working system, in which we illustrate a set of existing practical problems and how they could be handled. We believe this is essential in providing the basic understanding of P2P streaming systems. This paper uses a set of real traces and attempts to develop some theoretical basis to demonstrate that a random peer partnership selection with a hybrid pull-push scheme has the potentially to scale. Specifically, first, we describe the fundamental system design tradeoffs and key changes in the design of a Coolstreaming system including substreaming, buffer management, scheduling and the adopt of a hybrid pull-push mechanism over the original pull-based content delivery approach; second, we examine the overlay topology and its convergence; third, using a combination of real traces and analysis, we quantitatively provide the insights on how the buffering technique resolves the problems associated with dynamics and heterogeneity; fourth, we show how substream and path diversity can help to alleviate the impact from congestion and churns; fifth, we discuss the system scalability and limitations.
---
paper_title: Linear Programming Models For Multi-Channel P2P Streaming Systems

paper_content:

Most of the commercial P2P video streaming deployments support hundreds of channels and are referred to as multichannel systems. Measurement studies show that bandwidth resources of different channels are highly unbalanced and thus recent research studies have proposed various protocols to improve the streaming qualities for all channels by enabling cross-channel cooperation among multiple channels. However, there is no general framework for comparing existing and potential designs for multi-channel P2P systems. The goal of this paper is to establish tractable models for answering the fundamental question in multi-channel system designs: Under what circumstances, should a particular design be used to achieve the desired streaming quality with the lowest implementation complexity? To achieve this goal, we first classify existing and potential designs into three categories, namely Naive Bandwidth allocation Approach (NBA), Passive Channel-aware bandwidth allocation Approach (PCA) and Active Channel-aware bandwidth allocation Approach (ACA). Then, we define the bandwidth satisfaction ratio as a performance metric to develop linear programming models for the three designs. The proposed models are independent of implementations and can be efficiently solved due to the linear property, which provides a way of numerically exploring the design space of multi-channel systems and developing closedform solutions for special systems.
---
paper_title: A Survey on Peer-to-Peer Video Streaming Systems

paper_content:

Video-over-IP applications have recently attracted a large number of users on the Internet. Traditional client-server based video streaming solutions incur expensive bandwidth provision cost on the server. Peer-to-Peer (P2P) networking is a new paradigm to build distributed network applications. Recently, several P2P streaming systems have been deployed to provide live and on-demand video streaming services on the Internet at low server cost. In this paper, we provide a survey on the existing P2P solutions for live and on-demand video streaming. Representative P2P streaming systems, including tree, multi-tree and mesh based systems are introduced. We describe the challenges and solutions of providing live and on-demand video streaming in P2P environment. Open research issues on P2P video streaming are also discussed.
---
paper_title: P2VoD: providing fault tolerant video-on-demand streaming in peer-to-peer environment

paper_content:

We present a system for video-on-demand streaming in peer-to-peer environment. We start by realizing the major differences between two types of streaming: live and on-demand. These observations lead to a set of problems that need to be solved for a peer-to-peer video-on-demand system. To address these problems, we propose a solution, which includes detail algorithms for building and maintaining an application multicast tree. The novel ideas in this paper are the use of a new caching scheme at clients, and the introduction of generation for better client management. Performance study based on simulation is carried out. The results show that our system outperforms a recently proposed system in a number of important performance metrics.
---
paper_title: Multicast Video-on-Demand services

paper_content:

The server's storage I/O and network I/O bandwidths are the main bottleneck of VoD service. Multicast offers an efficient means of distributing a video program to multiple clients, thus greatly improving the VoD performance. However, there are many problems to overcome before development of multicast VoD systems. This paper critically evaluates and discusses the recent progress in developing multicast VoD systems. We first present the concept and architecture of multicast VoD, and then introduce the techniques used in multicast VoD systems. We also analyze and evaluate problems related to multicast VoD service. Finally, we present open issues on multicast VoD as possible future research directions.
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paper_title: Challenges, design and analysis of a large-scale p2p-vod system

paper_content:

P2P file downloading and streaming have already become very popular Internet applications. These systems dramatically reduce the server loading, and provide a platform for scalable content distribution, as long as there is interest for the content. P2P-based video-on-demand (P2P-VoD) is a new challenge for the P2P technology. Unlike streaming live content, P2P-VoD has less synchrony in the users sharing video content, therefore it is much more difficult to alleviate the server loading and at the same time maintaining the streaming performance. To compensate, a small storage is contributed by every peer, and new mechanisms for coordinating content replication, content discovery, and peer scheduling are carefully designed. In this paper, we describe and discuss the challenges and the architectural design issues of a large-scale P2P-VoD system based on the experiences of a real system deployed by PPLive. The system is also designed and instrumented with monitoring capability to measure both system and component specific performance metrics (for design improvements) as well as user satisfaction. After analyzing a large amount of collected data, we present a number of results on user behavior, various system performance metrics, including user satisfaction, and discuss what we observe based on the system design. The study of a real life system provides valuable insights for the future development of P2P-VoD technology.
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paper_title: Multicast routing in datagram internetworks and extended LANs

paper_content:

Multicasting, the transmission of a packet to a group of hosts, is an important service for improving the efficiency and robustness of distributed systems and applications. Although multicast capability is available and widely used in local area networks, when those LANs are interconnected by store-and-forward routers, the multicast service is usually not offered across the resulting internetwork . To address this limitation, we specify extensions to two common internetwork routing algorithms—distance-vector routing and link-state routing—to support low-delay datagram multicasting beyond a single LAN. We also describe modifications to the single-spanning-tree routing algorithm commonly used by link-layer bridges, to reduce the costs of multicasting in large extended LANs. Finally, we discuss how the use of multicast scope control and hierarchical multicast routing allows the multicast service to scale up to large internetworks.
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paper_title: Periodic broadcasting with VBR-encoded video

paper_content:

We consider designing near video on demand (VoD) systems that minimize start-up latency while maintaining high image quality. Recently non-uniform segmentation has been used to develop periodic broadcasting techniques for near VoD. These techniques give significant reductions in start-up latency as compared with more conventional uniform segmentation. All of these schemes assume, however, that the videos are CBR-encoded. Since a CBR-encoded video has a larger average rate than an open-loop VBR encoding with the same image quality, there is potential to obtain further performance improvements by using VBR video. In this paper we develop a series of multiplexing schemes for the periodic broadcasting of VBR-encoded video, which are based on smoothing, server buffering and client prefetching. Two key but conflicting performance measures exist when using VBR video: latency and packet loss. By introducing small additional delays in our multiplexing schemes, our traced-based numerical work shows that the schemes can achieve nearly 100% link utilization with negligible packet loss. When the ratio of the CBR rate to the VBR average rate is a modest 1.8, start-up latency can be reduced by a factor of four or more for common scenarios.
---
paper_title: SonicVoD: A VCR-supported P2P-VoD system with network coding

paper_content:

Video-on-demand (VoD) service on the Internet has been surprisingly popular during these years. And it is being greatly enhanced by the emergence and maturation of both the peer-to-peer (P2P) schema and network coding (NC) technology. P2P-based solution can make VoD systems obtain high scalability. The introduction of network coding improves the content distributing efficiency of the system. Meanwhile, digital video cassette recording (VCR) functionality provides users more freedom to choose playback mode while viewing video-clips. Designed a video segmentation-aided VCR support for P2P VoD system without network coding; and in ,we designed a P2P VoD system with scene-segmentation and network coding, which is called SonicVoD. In this paper, we will place our detailed design for SonicVoD and introduce some extensions for it.
---
paper_title: Modeling channel popularity dynamics in a large IPTV system

paper_content:

Understanding the channel popularity or content popularity is an important step in the workload characterization for modern information distribution systems (e.g., World Wide Web, peer-to-peer file-sharing systems, video-on-demand systems). In this paper, we focus on analyzing the channel popularity in the context of Internet Protocol Television (IPTV). In particular, we aim at capturing two important aspects of channel popularity - the distribution and temporal dynamics of the channel popularity. We conduct in-depth analysis on channel popularity on a large collection of user channel access data from a nation-wide commercial IPTV network. Based on the findings in our analysis, we choose a stochastic model that finds good matches in all attributes of interest with respect to the channel popularity. Furthermore, we propose a method to identify subsets of user population with inherently different channel interest. By tracking the change of population mixtures among different user classes, we extend our model to a multi-class population model, which enables us to capture the moderate diurnal popularity patterns exhibited in some channels. We also validate our channel popularity model using real user channel access data from commercial IPTV network.
---
paper_title: A hierarchical characterization of a live streaming media workload

paper_content:

We present a thorough characterization of what we believe to be the first significant live Internet streaming media workload in the scientific literature. Our characterization of over 3.5 million requests spanning a 28-day period is done at three increasingly granular levels, corresponding to clients, sessions, and transfers. Our findings support two important conclusions. First, we show that the nature of interactions between users and objects is fundamentally different for live versus stored objects. Access to stored objects is user driven, whereas access to live objects is object driven. This reversal of active/passive roles of users and objects leads to interesting dualities. For instance, our analysis underscores a Zipf-like profile for user interest in a given object, which is in contrast to the classic Zipf-like popularity of objects for a given user. Also, our analysis reveals that transfer lengths are highly variable and that this variability is due to client stickiness to a particular live object, as opposed to structural (size) properties of objects. Second, by contrasting two live streaming workloads from two radically different applications, we conjecture that some characteristics of live media access workloads are likely to be highly dependent on the nature of the live content being accessed. This dependence is clear from the strong temporal correlation observed in the traces, which we attribute to the impact of synchronous access to live content. Based on our analysis, we present a model for live media workload generation that incorporates many of our findings, and which we implement in GISMO.
---
paper_title: Measurement-based study on the relation between users' watching behavior and network sharing in P2P VoD systems

paper_content:

P2P-based Video on Demand (P2P VoD) systems can provide higher quality video services than P2P live systems. However, owing to the unavailability of open source codes, the characteristics of P2P VoD systems have not been fully explored. For this purpose, in this paper, we first implemented reverse engineering to the protocols of two most popular VoD systems used in China. Peers' watching behavior and network sharing were then studied through the measured buffer messages. Based on our study, we found that uploading-only peers were more than downloading peers, and smooth-watching peers were more than randomly-seeking peers in the current P2P VoD systems. This finding is significantly different from the existing P2P-based file dissemination systems and the results obtained in the previous work on VoD systems. Furthermore, this study revealed the relations between watching behavior and network sharing. It has been observed that randomly-seeking peers will provide more regular as well as rare chunks than smooth-watching peers. A simple mathematical model was established to analytically demonstrate the relation between the watching index (WI) distribution and network-sharing profile, and this relation was also validated by our measured data.
---
paper_title: DIGITAL VIDEO RECORDER-DRIVEN IMPACTS ON THE VIDEO CONTENT SERVICES INDUSTRY

paper_content:

Being part of a larger research program, this paper focuses on the impacts of so-called 'Digital Video Recorders' (DVRs) on the video content services industry. First, it gives a succinct definition of the video content services industry using the value chain as a metaphor. After laying a brief theoretical foundation on technological change and adoption, it considers the technological factors 'increased broadband connectivity to the home' and 'increased storage capacities' as change drivers in the video content services industry. The paper then highlights DVRs in detail (features, history, evolution, and viewer behavior) and investigates implications of a DVR roll-out for the different value propositions of players in the industry. It concludes with a brief outlook for the industry in the light of new technological developments.
---
paper_title: On next-generation telco-managed P2P TV architectures

paper_content:

In recent years, Telcos worldwide have deployed IPTV networks to offer cable TV-like services over the IP backbones. Such walled garden IPTV networks are provisioned to guarantee the quality of service, fast channel switching, and user experience expected by TV viewers. A common key design element of these networks is the use of IP multicast within a single network domain to broadcast several hundreds of TV channels to millions of receivers. However, as the amount of content and channels increase and users demand more interactive and asynchronous viewing, current IPTV architectures are showing clear limitations. In this paper, we study next-generation Telco-managed IPTV architectures, where P2P distributed systems are integrated in Telco's TV set-top boxes or home gateways. We explore how P2P can complement existing Telco-managed IPTV architectures to support advanced rewind functionalities and whether P2P can substitute IP multicast solutions towards supporting a potentially unlimited number of live channels. To this extent, we analyze the TV viewing behavior of a quarter million users using real traces from one of the largest Telco-managed IPTV networks in the world and show the synergistic strengths and the potential for various P2P IPTV combined architectures.
---
paper_title: Analysis of PPLive through active and passive measurements

paper_content:

The P2P-IPTV is an emerging class of Internet applications that is becoming very popular. The growing popularity of these rather bandwidth demanding multimedia streaming applications has the potential to flood the Internet with a huge amount of traffic.
---
paper_title: Traffic analysis of peer-to-peer IPTV communities

paper_content:

The Internet is currently experiencing one of the most important challenges in terms of content distribution since its first uses as a medium for content delivery: users from passive downloaders and browsers are moving towards content producers and publishers. They often distribute and retrieve multimedia contents establishing network communities. This is the case of peer-to-peer IPTV communities. In this work we present a detailed study of P2P IPTV traffic, providing useful insights on both transport- and packet-level properties as well as on the behavior of the peers inside the network. In particular, we provide novel results on the (i) ports and protocols used; (ii) differences between signaling and video traffic; (iii) behavior of the traffic at different time scales; (iv) differences between TCP and UDP traffic; (v) traffic generated and received by peers; (vi) peers neighborhood and session duration. The knowledge gained thanks to this analysis is useful for several tasks, e.g. traffic identification, understanding the performance of different P2P IPTV technologies and the impact of such traffic on network nodes and links, and building more realistic models for simulations.
---
paper_title: Measurement and modeling a large-scale overlay for multimedia streaming

paper_content:

This paper presents results from our measurement and modeling efforts on the large-scale peer-to-peer (p2p) overlay graphs spanned by the PPLive system which is arguably the most popular and largest multimedia streaming p2p system today. We believe that our findings can be used to understand large-scale p2p streaming systems for future planning of resource usage, and to provide useful and practical hints for future design of large-scale p2p streaming systems. Unlike other previous studies on PPLive, which focused on either network-centric or user-centric measurements of the system, our study is unique in (a) focusing on PPLive overlay-specific characteristics, and (b) being the first to derive mathematical models for its distributions of channel population size and session length. Our studies also reveal characteristics of multimedia streaming p2p overlays that are markedly different from existing file-sharing p2p overlays. Specifically, we find that: (1) Small PPLive overlays (as many as 500 nodes) are similar to random graphs in structure, (2) Average degree of a peer in the overlay (i.e., its out-degree) is independent of channel population size, (3) The availability correlation between PPLive peer pairs is bimodal, i.e., some pairs have highly correlated availability, while others have no correlation, (4) Unlike p2p file-sharing users, PPLive peers are impatient, (5) Session lengths (discretized, per channel) are typically geometrically distributed, (6) Channel Population Size variations are larger than in p2p file-sharing networks, yet they can be fitted with polynomial mathematical models. We conclude with a series of suggestions on how our findings can improve IPTV future design.
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paper_title: Modeling user activities in a large IPTV system

paper_content:

Internet Protocol Television (IPTV) has emerged as a new delivery method for TV. In contrast with native broadcast in traditional cable and satellite TV system, video streams in IPTV are encoded in IP packets and distributed using IP unicast and multicast. This new architecture has been strategically embraced by ISPs across the globe, recognizing the opportunity for new services and its potential toward a more interactive style of TV watching experience in the future. Since user activities such as channel switches in IPTV impose workload beyond local TV or set-top box (different from broadcast TV systems), it becomes essential to characterize and model the aggregate user activities in an IPTV network to support various system design and performance evaluation functions such as network capacity planning. In this work, we perform an in-depth study on several intrinsic characteristics of IPTV user activities by analyzing the real data collected from an operational nation-wide IPTV system. We further generalize the findings and develop a series of models for capturing both the probability distribution and time-dynamics of user activities. We then combine theses models to design an IPTV user activity workload generation tool called SIMUL WATCH, which takes a small number of input parameters and generates synthetic workload traces that mimic a set of real users watching IPTV. We validate all the models and the prototype of SIMUL WATCH using the real traces. In particular, we show that SIMUL WATCH can estimate the unicast and multicast traffic accurately, proving itself as a useful tool in driving the performance study in IPTV systems.
---
paper_title: A Measurement Study of a Large-Scale P2P IPTV System

paper_content:

An emerging Internet application, IPTV, has the potential to flood Internet access and backbone ISPs with massive amounts of new traffic. Although many architectures are possible for IPTV video distribution, several mesh-pull P2P architectures have been successfully deployed on the Internet. In order to gain insights into mesh-pull P2P IPTV systems and the traffic loads they place on ISPs, we have undertaken an in-depth measurement study of one of the most popular IPTV systems, namely, PPLive. We have developed a dedicated PPLive crawler, which enables us to study the global characteristics of the mesh-pull PPLive system. We have also collected extensive packet traces for various different measurement scenarios, including both campus access networks and residential access networks. The measurement results obtained through these platforms bring important insights into P2P IPTV systems. Specifically, our results show the following. 1) P2P IPTV users have the similar viewing behaviors as regular TV users. 2) During its session, a peer exchanges video data dynamically with a large number of peers. 3) A small set of super peers act as video proxy and contribute significantly to video data uploading. 4) Users in the measured P2P IPTV system still suffer from long start-up delays and playback lags, ranging from several seconds to a couple of minutes. Insights obtained in this study will be valuable for the development and deployment of future P2P IPTV systems.
---
paper_title: Modeling channel popularity dynamics in a large IPTV system

paper_content:

Understanding the channel popularity or content popularity is an important step in the workload characterization for modern information distribution systems (e.g., World Wide Web, peer-to-peer file-sharing systems, video-on-demand systems). In this paper, we focus on analyzing the channel popularity in the context of Internet Protocol Television (IPTV). In particular, we aim at capturing two important aspects of channel popularity - the distribution and temporal dynamics of the channel popularity. We conduct in-depth analysis on channel popularity on a large collection of user channel access data from a nation-wide commercial IPTV network. Based on the findings in our analysis, we choose a stochastic model that finds good matches in all attributes of interest with respect to the channel popularity. Furthermore, we propose a method to identify subsets of user population with inherently different channel interest. By tracking the change of population mixtures among different user classes, we extend our model to a multi-class population model, which enables us to capture the moderate diurnal popularity patterns exhibited in some channels. We also validate our channel popularity model using real user channel access data from commercial IPTV network.
---
paper_title: Characterizing PPStream across Internet

paper_content:

Since the appearance of various P2P IPTV systems which timely broadcast live streaming to peers, they have attracted millions of users from all over the world. It is reported that the online audience have reached more than 1.2 million in peak time by the official website of PPStream, one of the most popular IPTV system in China. However, at the same time the popularity of these systems make the amounts of video traffic grow exponentially. In order to study the global playback performance, users ' behaviors and network characteristics as well, we developed our dedicated crawler of PPStream. Based on the measurements, we make some extensive performance evaluation on this commercially successful P2P IPTV system, and some characteristics on geographic clustering, connection stability, arrival/departure pattern, playback quality, sharing ratio and topology have been revealed. We think these findings can help other researchers model such streaming systems and system operators make further optimizations.
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paper_title: Characterizing user behavior to improve quality of streaming service over p2p networks

paper_content:

The universal recognition that it is critical to improve the performance of existing systems and protocols with the understanding to practical service experiences motivates us to discuss this issue in the context of peer-to-peer (P2P) streaming. With the benefit of both practical traces from traditional client-server (C/S) service systems and logs from P2P live broadcasting system, in this paper we first characterize end user behaviors in terms of online duration and reveal the statistically positive correlation between elapsed online duration and expected remaining online time. Then we explore the feasibility to improve the quality of streaming service over P2P networks by proposing Low Disruption Tree Construction (LDTC) algorithm to take the online duration information into account when peers self-organize into the service overlay. The experiment results show that LDTC could achieve higher stability of video date delivery tree and in turn improve the quality of streaming service.
---
paper_title: Longer, Better: On Extending User Online Duration to Improve Quality of Streaming Service in P2P Networks

paper_content:

During recent years, the Internet has witnessed a rapid growth in deployment of peer to peer (P2P) based live media streaming systems. In this paper, we are motivated to investigate the problem of improving the streaming quality of service (QoS) of those systems by two universal recognitions: one is that the understanding to practical service experiences would benefit the performance enhancement, while the other is "the more, the better" design philosophy in P2P networks. As an interesting approach, we first retrieve the practical online duration information of end users from service traces in our GridMedia system, and then intentionally extend the online duration of each peer, which would result in a more stable peer overlay. The comparative simulations with original real-world traces and modified ones demonstrate that the quality of streaming service would be better if peers stay longer in the community. We claim that, this simple but positive result essentially validates both the influence of end users' behaviors and the need of an incentive to encourage users to spend more time in P2P live streaming systems.
---
paper_title: A hierarchical characterization of a live streaming media workload

paper_content:

We present a thorough characterization of what we believe to be the first significant live Internet streaming media workload in the scientific literature. Our characterization of over 3.5 million requests spanning a 28-day period is done at three increasingly granular levels, corresponding to clients, sessions, and transfers. Our findings support two important conclusions. First, we show that the nature of interactions between users and objects is fundamentally different for live versus stored objects. Access to stored objects is user driven, whereas access to live objects is object driven. This reversal of active/passive roles of users and objects leads to interesting dualities. For instance, our analysis underscores a Zipf-like profile for user interest in a given object, which is in contrast to the classic Zipf-like popularity of objects for a given user. Also, our analysis reveals that transfer lengths are highly variable and that this variability is due to client stickiness to a particular live object, as opposed to structural (size) properties of objects. Second, by contrasting two live streaming workloads from two radically different applications, we conjecture that some characteristics of live media access workloads are likely to be highly dependent on the nature of the live content being accessed. This dependence is clear from the strong temporal correlation observed in the traces, which we attribute to the impact of synchronous access to live content. Based on our analysis, we present a model for live media workload generation that incorporates many of our findings, and which we implement in GISMO.
---
paper_title: An Empirical Study of the Coolstreaming+ System

paper_content:

In recent years, there has been significant interest in adopting the peer-to-peer (P2P) technology for Internet live video streaming. There are primarily two reasons behind this development: the elimination of infrastructure support and the self-scaling property of P2P systems. The success of our system Coolstreaming represented one of the earliest large-scale P2P video streaming experiments. Since then, there have been several large-scale commercial deployments. With desirable content, these systems have the potential to scale orders of magnitude beyond the existing academic P2P prototypes. However, to transform this potential into reality, we need to understand the key design trade-offs and principles, as well as the design limitations of these systems. There are two main design decisions in a P2P streaming system: (i) How to form an overlay, and (ii) How to deliver the content. Coolstreaming adopts a gossiping protocol for overlay construction, and a swarm-based protocol for content delivery. While these protocols provide excellent flexibility and effectiveness in dealing with system dynamics and random failure, their impact on the performance and the system scalability remain less known. This paper takes an inside look at a commercial system based on the Coolstreaming, called Coolstreaming+. We explore its design choices and the impact of these choices on streaming performance. Specifically, by using internal traces generated by recent live broadcast events, we study the workload, performance, and dynamics of the system. Based on these traces, we show that (1) the churn is the most critical factor that affects the overall performance of the system, and (2) there is a highly skew resource distribution in P2P streaming systems, which has significant impact on resource allocation. We further discuss the impact of these observations on the system properties, and present solutions to deal with various design challenges. In particular, we suggest solutions to deal with the excessive start-up time and high failure rates during flash crowd, which are two of the main challenges any streaming system needs to address.
---
paper_title: Stable Peers: Existence, Importance, and Application in Peer-to-Peer Live Video Streaming

paper_content:

This paper presents a systematic in-depth study on the existence, importance, and application of stable nodes in peer- to-peer live video streaming. Using traces from a real large-scale system as well as analytical models, we show that, while the number of stable nodes is small throughout a whole session, their longer lifespans make them constitute a significant portion in a per-snapshot view of a peer-to-peer overlay. As a result, they have substantially affected the performance of the overall system. Inspired by this, we propose a tiered overlay design, with stable nodes being organized into a tier-1 backbone for serving tier-2 nodes. It offers a highly cost-effective and deployable alternative to proxy-assisted designs. We develop a comprehensive set of algorithms for stable node identification and organization. Specifically, we present a novel structure, Labeled Tree, for the tier-1 overlay, which, leveraging stable peers, simultaneously achieves low overhead and high transmission reliability. Our tiered framework flexibly accommodates diverse existing overlay structures in the second tier. Our extensive simulation results demonstrated that the customized optimization using selected stable nodes boosts the streaming quality and also effectively reduces the control overhead. This is further validated through prototype experiments over the PlanetLab network.
---
paper_title: An analysis of live streaming workloads on the internet

paper_content:

In this paper, we study the live streaming workload from a large content delivery network. Our data, collected over a 3 month period, contains over 70 million requests for 5,000 distinct URLs from clients in over 200 countries. To our knowledge, this is the most extensive data of live streaming on the Internet that has been studied to date. Our contributions are two-fold. First, we present a macroscopic analysis of the workload, characterizing popularity, arrival process, session duration, and transport protocol use. Our results show that popularity follows a 2-mode Zipf distribution, session interarrivals within small time-windows are exponential, session durations are heavy-tailed, and that UDP is far from having universal reach on the Internet. Second, we cover two additional characteristics that are more specific to the nature of live streaming applications: the diversity of clients in comparison to traditional broadcast media like radio and TV, and the phenomena that many clients regularly join recurring events. We find that Internet streaming does reach a wide audience, often spanning hundreds of AS domains and tens of countries. More interesting is that small streams also have a diverse audience. We also find that recurring users often have lifetimes of at least as long as one-third of the days in the event.
---
paper_title: Watching television over an IP network

paper_content:

For half a century, television has been a dominant and pervasive mass media, driving many technological advances. Despite its widespread usage and importance to emerging applications, the ingrained TV viewing habits are not completely understood. This was primarily due to the difficulty of instrumenting monitoring devices at individual homes at a large scale. The recent boom of Internet TV (IPTV) has enabled us to monitor the user behavior and network usage of an entire network. Such analysis can provide a clearer picture of how people watch TV and how the underlying networks and systems can better adapt to future challenges. In this paper, we present the first analysis of IPTV workloads based on network traces from one of the world's largest IPTV systems. Our dataset captures the channel change activities of 250,000 households over a six month period. We characterize the properties of viewing sessions, channel popularity dynamics, geographical locality, and channel switching behaviors. We discuss implications of our findings on networks and systems, including the support needed for fast channel changes. Our data analysis of an operational IPTV system has important implications on not only existing and future IPTV systems, but also the design of the open Internet TV distribution systems such as Joost and BBC's iPlayer that distribute television on the wider Internet.
---
paper_title: A Measurement Study of a Large-Scale P2P IPTV System

paper_content:

An emerging Internet application, IPTV, has the potential to flood Internet access and backbone ISPs with massive amounts of new traffic. Although many architectures are possible for IPTV video distribution, several mesh-pull P2P architectures have been successfully deployed on the Internet. In order to gain insights into mesh-pull P2P IPTV systems and the traffic loads they place on ISPs, we have undertaken an in-depth measurement study of one of the most popular IPTV systems, namely, PPLive. We have developed a dedicated PPLive crawler, which enables us to study the global characteristics of the mesh-pull PPLive system. We have also collected extensive packet traces for various different measurement scenarios, including both campus access networks and residential access networks. The measurement results obtained through these platforms bring important insights into P2P IPTV systems. Specifically, our results show the following. 1) P2P IPTV users have the similar viewing behaviors as regular TV users. 2) During its session, a peer exchanges video data dynamically with a large number of peers. 3) A small set of super peers act as video proxy and contribute significantly to video data uploading. 4) Users in the measured P2P IPTV system still suffer from long start-up delays and playback lags, ranging from several seconds to a couple of minutes. Insights obtained in this study will be valuable for the development and deployment of future P2P IPTV systems.
---
paper_title: Characterizing PPStream across Internet

paper_content:

Since the appearance of various P2P IPTV systems which timely broadcast live streaming to peers, they have attracted millions of users from all over the world. It is reported that the online audience have reached more than 1.2 million in peak time by the official website of PPStream, one of the most popular IPTV system in China. However, at the same time the popularity of these systems make the amounts of video traffic grow exponentially. In order to study the global playback performance, users ' behaviors and network characteristics as well, we developed our dedicated crawler of PPStream. Based on the measurements, we make some extensive performance evaluation on this commercially successful P2P IPTV system, and some characteristics on geographic clustering, connection stability, arrival/departure pattern, playback quality, sharing ratio and topology have been revealed. We think these findings can help other researchers model such streaming systems and system operators make further optimizations.
---
paper_title: An analysis of live streaming workloads on the internet

paper_content:

In this paper, we study the live streaming workload from a large content delivery network. Our data, collected over a 3 month period, contains over 70 million requests for 5,000 distinct URLs from clients in over 200 countries. To our knowledge, this is the most extensive data of live streaming on the Internet that has been studied to date. Our contributions are two-fold. First, we present a macroscopic analysis of the workload, characterizing popularity, arrival process, session duration, and transport protocol use. Our results show that popularity follows a 2-mode Zipf distribution, session interarrivals within small time-windows are exponential, session durations are heavy-tailed, and that UDP is far from having universal reach on the Internet. Second, we cover two additional characteristics that are more specific to the nature of live streaming applications: the diversity of clients in comparison to traditional broadcast media like radio and TV, and the phenomena that many clients regularly join recurring events. We find that Internet streaming does reach a wide audience, often spanning hundreds of AS domains and tens of countries. More interesting is that small streams also have a diverse audience. We also find that recurring users often have lifetimes of at least as long as one-third of the days in the event.
---
paper_title: Watching television over an IP network

paper_content:

For half a century, television has been a dominant and pervasive mass media, driving many technological advances. Despite its widespread usage and importance to emerging applications, the ingrained TV viewing habits are not completely understood. This was primarily due to the difficulty of instrumenting monitoring devices at individual homes at a large scale. The recent boom of Internet TV (IPTV) has enabled us to monitor the user behavior and network usage of an entire network. Such analysis can provide a clearer picture of how people watch TV and how the underlying networks and systems can better adapt to future challenges. In this paper, we present the first analysis of IPTV workloads based on network traces from one of the world's largest IPTV systems. Our dataset captures the channel change activities of 250,000 households over a six month period. We characterize the properties of viewing sessions, channel popularity dynamics, geographical locality, and channel switching behaviors. We discuss implications of our findings on networks and systems, including the support needed for fast channel changes. Our data analysis of an operational IPTV system has important implications on not only existing and future IPTV systems, but also the design of the open Internet TV distribution systems such as Joost and BBC's iPlayer that distribute television on the wider Internet.
---
paper_title: Improving quality of live streaming service over p2p networks with user behavior model

paper_content:

In this paper, we mainly investigate how to improve the streaming quality of service over Peer-to-Peer (P2P) networks with the benefit of practical service traces. Considering that the QoS of P2P live streaming is generally affected by high dynamics in peer community, we abstract the online duration model of end users and then exploit this characteristic to improve the stability and encourage contribution in P2P networks, which in turn facilitates the quality of streaming. ::: ::: The first effort involves the online information when constructing video delivery tree and hence achieves less playback disruption. The other algorithm takes the online duration into account when selecting neighbor peers for data exchange and advocates more mutual cooperation between peers. The experiment results show that the proposed schemes could respectively achieve higher stability and better delivery quality.
---
paper_title: Measurement and modeling a large-scale overlay for multimedia streaming

paper_content:

This paper presents results from our measurement and modeling efforts on the large-scale peer-to-peer (p2p) overlay graphs spanned by the PPLive system which is arguably the most popular and largest multimedia streaming p2p system today. We believe that our findings can be used to understand large-scale p2p streaming systems for future planning of resource usage, and to provide useful and practical hints for future design of large-scale p2p streaming systems. Unlike other previous studies on PPLive, which focused on either network-centric or user-centric measurements of the system, our study is unique in (a) focusing on PPLive overlay-specific characteristics, and (b) being the first to derive mathematical models for its distributions of channel population size and session length. Our studies also reveal characteristics of multimedia streaming p2p overlays that are markedly different from existing file-sharing p2p overlays. Specifically, we find that: (1) Small PPLive overlays (as many as 500 nodes) are similar to random graphs in structure, (2) Average degree of a peer in the overlay (i.e., its out-degree) is independent of channel population size, (3) The availability correlation between PPLive peer pairs is bimodal, i.e., some pairs have highly correlated availability, while others have no correlation, (4) Unlike p2p file-sharing users, PPLive peers are impatient, (5) Session lengths (discretized, per channel) are typically geometrically distributed, (6) Channel Population Size variations are larger than in p2p file-sharing networks, yet they can be fitted with polynomial mathematical models. We conclude with a series of suggestions on how our findings can improve IPTV future design.
---
paper_title: A measurement of a large-scale peer-to-peer live video streaming system

paper_content:

Peer-to-Peer (P2P) technologies have found much success in applications like file distributions, and its adoption in live video streaming has recently attracted significant attentions. With the emerge of commercial P2P streaming systems that are orders of magnitude larger than the academic systems, understanding its basic principles and limitations are important in the design of future systems. Coolstreaming represented one of the earliest large-scale live streaming trials in the Internet. In this paper, we discuss the fundamental design principles and examine the system dynamics. By leveraging the recent results obtained from live event broadcast, we develop some basis to demonstrate that a random partnership selection has the potential to scale. Specifically, first, we examine the overlay topology and how it converges. Second, using a combination of real traces and analysis, we quantitatively provide insights on how buffering technique resolves the problems associated with dynamics and heterogeneity. Third, we discuss the main limitations and the implications on the scalability.
---
paper_title: Measurements, analysis, and modeling of BitTorrent-like systems

paper_content:

Existing studies on BitTorrent systems are single-torrent based, while more than 85% of all peers participate in multiple torrents according to our trace analysis. In addition, these studies are not sufficiently insightful and accurate even for single-torrent models, due to some unrealistic assumptions. Our analysis of representative Bit-Torrent traffic provides several new findings regarding the limitations of BitTorrent systems: (1) Due to the exponentially decreasing peer arrival rate in reality, service availability in such systems becomes poor quickly, after which it is difficult for the file to be located and downloaded. (2) Client performance in the BitTorrent-like systems is unstable, and fluctuates widely with the peer population. (3) Existing systems could provide unfair services to peers, where peers with high downloading speed tend to download more and upload less. In this paper, we study these limitations on torrent evolution in realistic environments. Motivated by the analysis and modeling results, we further build a graph based multi-torrent model to study inter-torrent collaboration. Our model quantitatively provides strong motivation for inter-torrent collaboration instead of directly stimulating seeds to stay longer. We also discuss a system design to show the feasibility of multi-torrent collaboration.
---
paper_title: Modeling user activities in a large IPTV system

paper_content:

Internet Protocol Television (IPTV) has emerged as a new delivery method for TV. In contrast with native broadcast in traditional cable and satellite TV system, video streams in IPTV are encoded in IP packets and distributed using IP unicast and multicast. This new architecture has been strategically embraced by ISPs across the globe, recognizing the opportunity for new services and its potential toward a more interactive style of TV watching experience in the future. Since user activities such as channel switches in IPTV impose workload beyond local TV or set-top box (different from broadcast TV systems), it becomes essential to characterize and model the aggregate user activities in an IPTV network to support various system design and performance evaluation functions such as network capacity planning. In this work, we perform an in-depth study on several intrinsic characteristics of IPTV user activities by analyzing the real data collected from an operational nation-wide IPTV system. We further generalize the findings and develop a series of models for capturing both the probability distribution and time-dynamics of user activities. We then combine theses models to design an IPTV user activity workload generation tool called SIMUL WATCH, which takes a small number of input parameters and generates synthetic workload traces that mimic a set of real users watching IPTV. We validate all the models and the prototype of SIMUL WATCH using the real traces. In particular, we show that SIMUL WATCH can estimate the unicast and multicast traffic accurately, proving itself as a useful tool in driving the performance study in IPTV systems.
---
paper_title: A Measurement Study of a Large-Scale P2P IPTV System

paper_content:

An emerging Internet application, IPTV, has the potential to flood Internet access and backbone ISPs with massive amounts of new traffic. Although many architectures are possible for IPTV video distribution, several mesh-pull P2P architectures have been successfully deployed on the Internet. In order to gain insights into mesh-pull P2P IPTV systems and the traffic loads they place on ISPs, we have undertaken an in-depth measurement study of one of the most popular IPTV systems, namely, PPLive. We have developed a dedicated PPLive crawler, which enables us to study the global characteristics of the mesh-pull PPLive system. We have also collected extensive packet traces for various different measurement scenarios, including both campus access networks and residential access networks. The measurement results obtained through these platforms bring important insights into P2P IPTV systems. Specifically, our results show the following. 1) P2P IPTV users have the similar viewing behaviors as regular TV users. 2) During its session, a peer exchanges video data dynamically with a large number of peers. 3) A small set of super peers act as video proxy and contribute significantly to video data uploading. 4) Users in the measured P2P IPTV system still suffer from long start-up delays and playback lags, ranging from several seconds to a couple of minutes. Insights obtained in this study will be valuable for the development and deployment of future P2P IPTV systems.
---
paper_title: Modeling channel popularity dynamics in a large IPTV system

paper_content:

Understanding the channel popularity or content popularity is an important step in the workload characterization for modern information distribution systems (e.g., World Wide Web, peer-to-peer file-sharing systems, video-on-demand systems). In this paper, we focus on analyzing the channel popularity in the context of Internet Protocol Television (IPTV). In particular, we aim at capturing two important aspects of channel popularity - the distribution and temporal dynamics of the channel popularity. We conduct in-depth analysis on channel popularity on a large collection of user channel access data from a nation-wide commercial IPTV network. Based on the findings in our analysis, we choose a stochastic model that finds good matches in all attributes of interest with respect to the channel popularity. Furthermore, we propose a method to identify subsets of user population with inherently different channel interest. By tracking the change of population mixtures among different user classes, we extend our model to a multi-class population model, which enables us to capture the moderate diurnal popularity patterns exhibited in some channels. We also validate our channel popularity model using real user channel access data from commercial IPTV network.
---
paper_title: Inside the New Coolstreaming: Principles, Measurements and Performance Implications

paper_content:

The peer-to-peer (P2P) based video streaming has emerged as a promising solution for Internet video distribution. Leveraging the resource available at end users, this approach poses great potential to scale in the Internet. We have now seen the commercial P2P streaming systems that are orders of magnitude larger than the earlier academic systems. We believe understanding its basic principles and limitations are important in the design of future systems. The Coolstreaming, first released in summer 2004, arguably represented the first successful large-scale P2P live streaming system. Since then, the system has been significantly modified and commercially launched. This paper takes an inside look at the new Coolstreaming system by exposing its design options and rationale behind them, and examines their implications on streaming performance. Specifically, by leveraging a large set of traces obtained from recent live event broadcast and extensive simulations, we study the workload characteristics, system dynamics, and impact from a variety of system parameters. We demonstrate that there is a highly skewed resource distribution in such systems and the performance is mostly affected by the system dynamics. In addition, we show that there are inherent correlations and fundamental trade-off among different system parameters, which can be further explored to enhance the system performance.
---
paper_title: Characterizing PPStream across Internet

paper_content:

Since the appearance of various P2P IPTV systems which timely broadcast live streaming to peers, they have attracted millions of users from all over the world. It is reported that the online audience have reached more than 1.2 million in peak time by the official website of PPStream, one of the most popular IPTV system in China. However, at the same time the popularity of these systems make the amounts of video traffic grow exponentially. In order to study the global playback performance, users ' behaviors and network characteristics as well, we developed our dedicated crawler of PPStream. Based on the measurements, we make some extensive performance evaluation on this commercially successful P2P IPTV system, and some characteristics on geographic clustering, connection stability, arrival/departure pattern, playback quality, sharing ratio and topology have been revealed. We think these findings can help other researchers model such streaming systems and system operators make further optimizations.
---
paper_title: Characterizing user behavior to improve quality of streaming service over p2p networks

paper_content:

The universal recognition that it is critical to improve the performance of existing systems and protocols with the understanding to practical service experiences motivates us to discuss this issue in the context of peer-to-peer (P2P) streaming. With the benefit of both practical traces from traditional client-server (C/S) service systems and logs from P2P live broadcasting system, in this paper we first characterize end user behaviors in terms of online duration and reveal the statistically positive correlation between elapsed online duration and expected remaining online time. Then we explore the feasibility to improve the quality of streaming service over P2P networks by proposing Low Disruption Tree Construction (LDTC) algorithm to take the online duration information into account when peers self-organize into the service overlay. The experiment results show that LDTC could achieve higher stability of video date delivery tree and in turn improve the quality of streaming service.
---
paper_title: A hierarchical characterization of a live streaming media workload

paper_content:

We present a thorough characterization of what we believe to be the first significant live Internet streaming media workload in the scientific literature. Our characterization of over 3.5 million requests spanning a 28-day period is done at three increasingly granular levels, corresponding to clients, sessions, and transfers. Our findings support two important conclusions. First, we show that the nature of interactions between users and objects is fundamentally different for live versus stored objects. Access to stored objects is user driven, whereas access to live objects is object driven. This reversal of active/passive roles of users and objects leads to interesting dualities. For instance, our analysis underscores a Zipf-like profile for user interest in a given object, which is in contrast to the classic Zipf-like popularity of objects for a given user. Also, our analysis reveals that transfer lengths are highly variable and that this variability is due to client stickiness to a particular live object, as opposed to structural (size) properties of objects. Second, by contrasting two live streaming workloads from two radically different applications, we conjecture that some characteristics of live media access workloads are likely to be highly dependent on the nature of the live content being accessed. This dependence is clear from the strong temporal correlation observed in the traces, which we attribute to the impact of synchronous access to live content. Based on our analysis, we present a model for live media workload generation that incorporates many of our findings, and which we implement in GISMO.
---
paper_title: An Empirical Study of the Coolstreaming+ System

paper_content:

In recent years, there has been significant interest in adopting the peer-to-peer (P2P) technology for Internet live video streaming. There are primarily two reasons behind this development: the elimination of infrastructure support and the self-scaling property of P2P systems. The success of our system Coolstreaming represented one of the earliest large-scale P2P video streaming experiments. Since then, there have been several large-scale commercial deployments. With desirable content, these systems have the potential to scale orders of magnitude beyond the existing academic P2P prototypes. However, to transform this potential into reality, we need to understand the key design trade-offs and principles, as well as the design limitations of these systems. There are two main design decisions in a P2P streaming system: (i) How to form an overlay, and (ii) How to deliver the content. Coolstreaming adopts a gossiping protocol for overlay construction, and a swarm-based protocol for content delivery. While these protocols provide excellent flexibility and effectiveness in dealing with system dynamics and random failure, their impact on the performance and the system scalability remain less known. This paper takes an inside look at a commercial system based on the Coolstreaming, called Coolstreaming+. We explore its design choices and the impact of these choices on streaming performance. Specifically, by using internal traces generated by recent live broadcast events, we study the workload, performance, and dynamics of the system. Based on these traces, we show that (1) the churn is the most critical factor that affects the overall performance of the system, and (2) there is a highly skew resource distribution in P2P streaming systems, which has significant impact on resource allocation. We further discuss the impact of these observations on the system properties, and present solutions to deal with various design challenges. In particular, we suggest solutions to deal with the excessive start-up time and high failure rates during flash crowd, which are two of the main challenges any streaming system needs to address.
---
paper_title: Watching television over an IP network

paper_content:

For half a century, television has been a dominant and pervasive mass media, driving many technological advances. Despite its widespread usage and importance to emerging applications, the ingrained TV viewing habits are not completely understood. This was primarily due to the difficulty of instrumenting monitoring devices at individual homes at a large scale. The recent boom of Internet TV (IPTV) has enabled us to monitor the user behavior and network usage of an entire network. Such analysis can provide a clearer picture of how people watch TV and how the underlying networks and systems can better adapt to future challenges. In this paper, we present the first analysis of IPTV workloads based on network traces from one of the world's largest IPTV systems. Our dataset captures the channel change activities of 250,000 households over a six month period. We characterize the properties of viewing sessions, channel popularity dynamics, geographical locality, and channel switching behaviors. We discuss implications of our findings on networks and systems, including the support needed for fast channel changes. Our data analysis of an operational IPTV system has important implications on not only existing and future IPTV systems, but also the design of the open Internet TV distribution systems such as Joost and BBC's iPlayer that distribute television on the wider Internet.
---
paper_title: Characterizing user access to videos on the World Wide Web

paper_content:

Despite evidence of rising popularity of video on the web (or VOW), little is known about how users access video. However, such a characterization can greatly benefit the design of multimedia systems such as web video proxies and VOW servers. Hence, this paper presents an analysis of trace data obtained from an ongoing VOW experiment in Lulea University of Technology, Sweden. This experiment is unique as video material is distributed over a high bandwidth network allowing users to make access decisions without the network being a major factor. Our analysis revealed a number of interesting discoveries regarding user VOW access. For example, accesses display high temporal locality: several requests for the same video title often occur within a short time span. Accesses also exhibited spatial locality of reference whereby a small number of machines accounted for a large number of overall requests. Another finding was a browsing pattern where users preview the initial portion of a video to find out if they are interested. If they like it, they continue watching, otherwise they halt it. This pattern suggests that caching the first several minutes of video data should prove effective. Lastly, the analysis shows that, contrary to previous studies, ranking of video titles by popularity did not fit a Zipfian distribution.
---
paper_title: Characterising User Interactivity for Sports Video-on-Demand

paper_content:

This paper presents a detailed characterisation of user behaviour for a series of interactive sport videos from the 2006 FIFA World Cup. In addition to generic VCR-like features, our custom-built Video-on-Demand architecture enabled us to provide advanced interactivity features such as bookmarking. We illustrate how such functionality may have a dramatic impact on how users consume content. A detailed discussion is also provided on how content distributors may turn this knowledge to their advantage, and thus increase the efficiency of their delivery networks.
---
paper_title: Challenges, design and analysis of a large-scale p2p-vod system

paper_content:

P2P file downloading and streaming have already become very popular Internet applications. These systems dramatically reduce the server loading, and provide a platform for scalable content distribution, as long as there is interest for the content. P2P-based video-on-demand (P2P-VoD) is a new challenge for the P2P technology. Unlike streaming live content, P2P-VoD has less synchrony in the users sharing video content, therefore it is much more difficult to alleviate the server loading and at the same time maintaining the streaming performance. To compensate, a small storage is contributed by every peer, and new mechanisms for coordinating content replication, content discovery, and peer scheduling are carefully designed. In this paper, we describe and discuss the challenges and the architectural design issues of a large-scale P2P-VoD system based on the experiences of a real system deployed by PPLive. The system is also designed and instrumented with monitoring capability to measure both system and component specific performance metrics (for design improvements) as well as user satisfaction. After analyzing a large amount of collected data, we present a number of results on user behavior, various system performance metrics, including user satisfaction, and discuss what we observe based on the system design. The study of a real life system provides valuable insights for the future development of P2P-VoD technology.
---
paper_title: Evaluation and optimization of a peer-to-peer video-on-demand system

paper_content:

Video-on-demand (VoD) is increasingly popular with internet users. However, VoD is costly due to the load placed on video servers. Peer-to-peer (P2P) techniques are an approach to alleviating server load through peer-assisted sharing. Existing studies on P2P VoD are mostly based on simulation and focus on areas such as overlay topology, but little is known about the effectiveness of P2P in a real VoD system. In this paper we present a comprehensive measurement study of GridCast, a deployed experimental P2P VoD system. Using a 2-month log of GridCast, we evaluate its scalability and end user experience. Motivated by the observations on user behavior and unused peer resource, we further optimize its performance. Our key findings are: (1) a moderate number of concurrent users can derive satisfactory user experience. However, good network bandwidth at peers and adequate server provisioning are still critical to good user experience; (2) a simple prefetching algorithm can be effective to improve random seeks; (3) a simple caching across multiple videos has great potential to further improve system scalability. Overall, we believe that it is feasible to provide a cost-effective P2P VoD service with acceptable user experience, and there is a fundamental tradeoff between good user experience and system scalability.
---
paper_title: Understanding user behavior in large-scale video-on-demand systems

paper_content:

Video-on-demand over IP (VOD) is one of the best-known examples of "next-generation" Internet applications cited as a goal by networking and multimedia researchers. Without empirical data, researchers have generally relied on simulated models to drive their design and developmental efforts. In this paper, we present one of the first measurement studies of a large VOD system, using data covering 219 days and more than 150,000 users in a VOD system deployed by China Telecom. Our study focuses on user behavior, content access patterns, and their implications on the design of multimedia streaming systems. Our results also show that when used to model the user-arrival rate, the traditional Poisson model is conservative and overestimates the probability of large arrival groups. We introduce a modified Poisson distribution that more accurately models our observations. We also observe a surprising result, that video session lengths has a weak inverse correlation with the video's popularity. Finally, we gain better understanding of the sources of video popularity through analysis of a number of internal and external factors.
---
paper_title: User behavior analysis of a video-on-demand service with a wide variety of subjects and lengths

paper_content:

This paper presents the analysis performed on the www.lne.es video-on-demand service (LNE TV), which is part of the digital version of one of the most important newspapers in Spain. Its principal special characteristic is the wide range of subjects (news, music, culture, tourism, nature, sports, etc) and lengths of the offered contents (from 2 minutes to 2 hours), which make it an interesting case study. Elements about user behavior have been analyzed such as session analysis; delivered time, pause distribution, jumps length, etc. The study points out interesting results about length dependence, interactions appearing, popularity of the videos, etc., which are compared with the results obtained in previous works, generally developed on educational environments (services or users). A behavior user model has been performed using the results of the analyses. This model is oriented to services with different types of information and lengths for the videos. This study has been performed thanks to an access log database with more than 150,000 requests of almost 900 videos stored over a period of 4 years. The conclusions of the study are essential to improve the service configuration and content selection. Moreover, they can be used to develop service models for video-on-demand services, which can help administrators to predict future situations and avoid performance problems.
---
paper_title: Characterizing user access to videos on the World Wide Web

paper_content:

Despite evidence of rising popularity of video on the web (or VOW), little is known about how users access video. However, such a characterization can greatly benefit the design of multimedia systems such as web video proxies and VOW servers. Hence, this paper presents an analysis of trace data obtained from an ongoing VOW experiment in Lulea University of Technology, Sweden. This experiment is unique as video material is distributed over a high bandwidth network allowing users to make access decisions without the network being a major factor. Our analysis revealed a number of interesting discoveries regarding user VOW access. For example, accesses display high temporal locality: several requests for the same video title often occur within a short time span. Accesses also exhibited spatial locality of reference whereby a small number of machines accounted for a large number of overall requests. Another finding was a browsing pattern where users preview the initial portion of a video to find out if they are interested. If they like it, they continue watching, otherwise they halt it. This pattern suggests that caching the first several minutes of video data should prove effective. Lastly, the analysis shows that, contrary to previous studies, ranking of video titles by popularity did not fit a Zipfian distribution.
---
paper_title: Characterising User Interactivity for Sports Video-on-Demand

paper_content:

This paper presents a detailed characterisation of user behaviour for a series of interactive sport videos from the 2006 FIFA World Cup. In addition to generic VCR-like features, our custom-built Video-on-Demand architecture enabled us to provide advanced interactivity features such as bookmarking. We illustrate how such functionality may have a dramatic impact on how users consume content. A detailed discussion is also provided on how content distributors may turn this knowledge to their advantage, and thus increase the efficiency of their delivery networks.
---
paper_title: Challenges, design and analysis of a large-scale p2p-vod system

paper_content:

P2P file downloading and streaming have already become very popular Internet applications. These systems dramatically reduce the server loading, and provide a platform for scalable content distribution, as long as there is interest for the content. P2P-based video-on-demand (P2P-VoD) is a new challenge for the P2P technology. Unlike streaming live content, P2P-VoD has less synchrony in the users sharing video content, therefore it is much more difficult to alleviate the server loading and at the same time maintaining the streaming performance. To compensate, a small storage is contributed by every peer, and new mechanisms for coordinating content replication, content discovery, and peer scheduling are carefully designed. In this paper, we describe and discuss the challenges and the architectural design issues of a large-scale P2P-VoD system based on the experiences of a real system deployed by PPLive. The system is also designed and instrumented with monitoring capability to measure both system and component specific performance metrics (for design improvements) as well as user satisfaction. After analyzing a large amount of collected data, we present a number of results on user behavior, various system performance metrics, including user satisfaction, and discuss what we observe based on the system design. The study of a real life system provides valuable insights for the future development of P2P-VoD technology.
---
paper_title: Understanding user behavior in large-scale video-on-demand systems

paper_content:

Video-on-demand over IP (VOD) is one of the best-known examples of "next-generation" Internet applications cited as a goal by networking and multimedia researchers. Without empirical data, researchers have generally relied on simulated models to drive their design and developmental efforts. In this paper, we present one of the first measurement studies of a large VOD system, using data covering 219 days and more than 150,000 users in a VOD system deployed by China Telecom. Our study focuses on user behavior, content access patterns, and their implications on the design of multimedia streaming systems. Our results also show that when used to model the user-arrival rate, the traditional Poisson model is conservative and overestimates the probability of large arrival groups. We introduce a modified Poisson distribution that more accurately models our observations. We also observe a surprising result, that video session lengths has a weak inverse correlation with the video's popularity. Finally, we gain better understanding of the sources of video popularity through analysis of a number of internal and external factors.
---
paper_title: Probabilistic analysis and interdependence discovery in the user interactions of a video news on demand service

paper_content:

Accurate workload prediction in multimedia systems requires a description of both its probabilistic properties and the interdependence between the variables of the system. This paper analyzes the interactions of the users of a news and entertainment video-on-demand service (LNE TV, http://tv.lne.es) during six months of activity. The analysis was performed using information extracted from the server logs, analyzing more than 300,000 requests for almost 1500 videos. The type of content on the site and the structure of LNE TV, which is similar to most Internet news services supported by a traditional newspaper, make this work an interesting case study, and the results can be easily extrapolated to similar audio/video streaming services. This paper shows that client interactivity in multimedia systems has the dependence structure of a stochastic process. In previous work, this type of study has been carried out in a single variable, whereas the user interactions in actual multimedia systems are multivariate. In this context, we have used copulas to create distributions to model correlated data. In our study, we model user interactions depending on their marginal univariate distributions and their correlation coefficient with the length of the videos.
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paper_title: User behavior analysis of a video-on-demand service with a wide variety of subjects and lengths

paper_content:

This paper presents the analysis performed on the www.lne.es video-on-demand service (LNE TV), which is part of the digital version of one of the most important newspapers in Spain. Its principal special characteristic is the wide range of subjects (news, music, culture, tourism, nature, sports, etc) and lengths of the offered contents (from 2 minutes to 2 hours), which make it an interesting case study. Elements about user behavior have been analyzed such as session analysis; delivered time, pause distribution, jumps length, etc. The study points out interesting results about length dependence, interactions appearing, popularity of the videos, etc., which are compared with the results obtained in previous works, generally developed on educational environments (services or users). A behavior user model has been performed using the results of the analyses. This model is oriented to services with different types of information and lengths for the videos. This study has been performed thanks to an access log database with more than 150,000 requests of almost 900 videos stored over a period of 4 years. The conclusions of the study are essential to improve the service configuration and content selection. Moreover, they can be used to develop service models for video-on-demand services, which can help administrators to predict future situations and avoid performance problems.
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paper_title: Distribution of Video-on-Demand Service over Cable Television Networks

paper_content:

The paper deals with investigations carried out to increase the effectiveness of video-on-demand (VoD) systems when cable television networks are used. A comparative analysis of the existing VoD architectures is made with respect to the equipment cost and the traffic load over the central transport network. Through statistical studies the main characteristics of a particular hybrid VoD are determined (such as twenty-four-hour distribution of the video traffic, average inter-arrival time of the VoD requests, average duration of video streams demanded, movies distribution according to the subscribers’ preferences). An algorithm for the videocontent flexible distribution among the distribution hubs is suggested. Thus a higher effectiveness of the system is achieved without significantly increasing the equipment cost.
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paper_title: On Feasibility of P2P On-Demand Streaming via Empirical VoD User Behavior Analysis

paper_content:

In its current art, peer-to-peer streaming solution has been mainly employed in the domain of live event broadcasting. In such a paradigm, users are required to simultaneously participate the streaming, which yields tremendous bandwidth pool to alleviate the server load. However, little effort has been paid to study the performance gain when peer-to-peer solution is deployed into the domain of Video-on-Demand (VoD) applications, when users have the freedom to access a large pool of media files at their preferred times. Users of VoD applications exhibit file-dependent and time-varying access patterns, which are hard to simulate without realistic guidance from the operational system observation. In this paper, we present an empirical study on the traces collected by the Vanderbilt University media streaming service over a period of 8 months. We pay special attention to peer aggregation around one media file, in which peer-to-peer streaming is able to play an essential role. With this regard, we investigate three key factors: file popularity, request inter-arrival time, and user online duration. Our analysis proves the existence of skewed file popularity, concentrated user requests, and long enough online duration. Furthermore, through replaying the trace via simulation, we show that peer-to-peer streaming could reduce the server load by as high as 90% over popular files.
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paper_title: Characterizing user access to videos on the World Wide Web

paper_content:

Despite evidence of rising popularity of video on the web (or VOW), little is known about how users access video. However, such a characterization can greatly benefit the design of multimedia systems such as web video proxies and VOW servers. Hence, this paper presents an analysis of trace data obtained from an ongoing VOW experiment in Lulea University of Technology, Sweden. This experiment is unique as video material is distributed over a high bandwidth network allowing users to make access decisions without the network being a major factor. Our analysis revealed a number of interesting discoveries regarding user VOW access. For example, accesses display high temporal locality: several requests for the same video title often occur within a short time span. Accesses also exhibited spatial locality of reference whereby a small number of machines accounted for a large number of overall requests. Another finding was a browsing pattern where users preview the initial portion of a video to find out if they are interested. If they like it, they continue watching, otherwise they halt it. This pattern suggests that caching the first several minutes of video data should prove effective. Lastly, the analysis shows that, contrary to previous studies, ranking of video titles by popularity did not fit a Zipfian distribution.
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paper_title: Characterizing user behavior model to evaluate hard cache in peer-to-peer based video-on-demand service

paper_content:

Peer-to-peer (P2P) based video-on-demand (VoD) systems rely on the cooperation among peers to reduce the server workload. Recently, hard cache is used to further improve the system scalability, because the contents will not be immediately cleaned up when the users get offline. However, how many practical benefits hard cache will bring to the P2P based VoD service has not been well studied and still remains far from clear. In this paper, we first characterize user behavior model with the benefit of millions of real VoD traces and identify several practical factors which potentially impact the system performance. Then we further conduct extensive trace-driven simulations to evaluate the scalability of P2P based VoD system with hard cache enabled and some interesting results are found.
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paper_title: Challenges, design and analysis of a large-scale p2p-vod system

paper_content:

P2P file downloading and streaming have already become very popular Internet applications. These systems dramatically reduce the server loading, and provide a platform for scalable content distribution, as long as there is interest for the content. P2P-based video-on-demand (P2P-VoD) is a new challenge for the P2P technology. Unlike streaming live content, P2P-VoD has less synchrony in the users sharing video content, therefore it is much more difficult to alleviate the server loading and at the same time maintaining the streaming performance. To compensate, a small storage is contributed by every peer, and new mechanisms for coordinating content replication, content discovery, and peer scheduling are carefully designed. In this paper, we describe and discuss the challenges and the architectural design issues of a large-scale P2P-VoD system based on the experiences of a real system deployed by PPLive. The system is also designed and instrumented with monitoring capability to measure both system and component specific performance metrics (for design improvements) as well as user satisfaction. After analyzing a large amount of collected data, we present a number of results on user behavior, various system performance metrics, including user satisfaction, and discuss what we observe based on the system design. The study of a real life system provides valuable insights for the future development of P2P-VoD technology.
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paper_title: Evaluation and optimization of a peer-to-peer video-on-demand system

paper_content:

Video-on-demand (VoD) is increasingly popular with internet users. However, VoD is costly due to the load placed on video servers. Peer-to-peer (P2P) techniques are an approach to alleviating server load through peer-assisted sharing. Existing studies on P2P VoD are mostly based on simulation and focus on areas such as overlay topology, but little is known about the effectiveness of P2P in a real VoD system. In this paper we present a comprehensive measurement study of GridCast, a deployed experimental P2P VoD system. Using a 2-month log of GridCast, we evaluate its scalability and end user experience. Motivated by the observations on user behavior and unused peer resource, we further optimize its performance. Our key findings are: (1) a moderate number of concurrent users can derive satisfactory user experience. However, good network bandwidth at peers and adequate server provisioning are still critical to good user experience; (2) a simple prefetching algorithm can be effective to improve random seeks; (3) a simple caching across multiple videos has great potential to further improve system scalability. Overall, we believe that it is feasible to provide a cost-effective P2P VoD service with acceptable user experience, and there is a fundamental tradeoff between good user experience and system scalability.
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paper_title: Understanding user behavior in large-scale video-on-demand systems

paper_content:

Video-on-demand over IP (VOD) is one of the best-known examples of "next-generation" Internet applications cited as a goal by networking and multimedia researchers. Without empirical data, researchers have generally relied on simulated models to drive their design and developmental efforts. In this paper, we present one of the first measurement studies of a large VOD system, using data covering 219 days and more than 150,000 users in a VOD system deployed by China Telecom. Our study focuses on user behavior, content access patterns, and their implications on the design of multimedia streaming systems. Our results also show that when used to model the user-arrival rate, the traditional Poisson model is conservative and overestimates the probability of large arrival groups. We introduce a modified Poisson distribution that more accurately models our observations. We also observe a surprising result, that video session lengths has a weak inverse correlation with the video's popularity. Finally, we gain better understanding of the sources of video popularity through analysis of a number of internal and external factors.
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paper_title: User behavior analysis of a video-on-demand service with a wide variety of subjects and lengths

paper_content:

This paper presents the analysis performed on the www.lne.es video-on-demand service (LNE TV), which is part of the digital version of one of the most important newspapers in Spain. Its principal special characteristic is the wide range of subjects (news, music, culture, tourism, nature, sports, etc) and lengths of the offered contents (from 2 minutes to 2 hours), which make it an interesting case study. Elements about user behavior have been analyzed such as session analysis; delivered time, pause distribution, jumps length, etc. The study points out interesting results about length dependence, interactions appearing, popularity of the videos, etc., which are compared with the results obtained in previous works, generally developed on educational environments (services or users). A behavior user model has been performed using the results of the analyses. This model is oriented to services with different types of information and lengths for the videos. This study has been performed thanks to an access log database with more than 150,000 requests of almost 900 videos stored over a period of 4 years. The conclusions of the study are essential to improve the service configuration and content selection. Moreover, they can be used to develop service models for video-on-demand services, which can help administrators to predict future situations and avoid performance problems.
---
paper_title: On Feasibility of P2P On-Demand Streaming via Empirical VoD User Behavior Analysis

paper_content:

In its current art, peer-to-peer streaming solution has been mainly employed in the domain of live event broadcasting. In such a paradigm, users are required to simultaneously participate the streaming, which yields tremendous bandwidth pool to alleviate the server load. However, little effort has been paid to study the performance gain when peer-to-peer solution is deployed into the domain of Video-on-Demand (VoD) applications, when users have the freedom to access a large pool of media files at their preferred times. Users of VoD applications exhibit file-dependent and time-varying access patterns, which are hard to simulate without realistic guidance from the operational system observation. In this paper, we present an empirical study on the traces collected by the Vanderbilt University media streaming service over a period of 8 months. We pay special attention to peer aggregation around one media file, in which peer-to-peer streaming is able to play an essential role. With this regard, we investigate three key factors: file popularity, request inter-arrival time, and user online duration. Our analysis proves the existence of skewed file popularity, concentrated user requests, and long enough online duration. Furthermore, through replaying the trace via simulation, we show that peer-to-peer streaming could reduce the server load by as high as 90% over popular files.
---
paper_title: User behavior anticipation in P2P live video streaming systems through a Bayesian network

paper_content:

In recent years, Peer-to-Peer (P2P) architectures have emerged as a scalable, low cost and easily deployable solution for live video streaming applications. In these systems, the load of video transmission is distributed over end-hosts by enabling them to relay the content to each other. Since end-hosts are controlled by users, their behavior directly impact the performance of the system. To understand it, massive measurement campaigns covering large-scale systems and long time periods have been performed. In this paper, we gathered and synthesized results obtained through these measurements and propose a Bayesian network that captures and integrates all of them into a synthetic model. We apply this model to the anticipation of peer departures which is an important challenge toward the performance improvement of these systems and especially churn resilience. The validation of our proposal is performed through intensive simulations that consider a streaming system composed of thousand users over two hundred days. We especially study two deployment scenarios: a system-scale one and a local one. We also compare our proposal with two standard estimators and we show under which conditions an estimator outperforms the others.
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paper_title: A Semi-Markovian Individual Model of Users for P2P Video Streaming Applications

paper_content:

P2P-based live video streaming has become one of the major applications on the Internet. Due to the importance of the user behavior in these systems, intensive measurement studies have been performed over them in order to provide global models. However, in real networks the individual user behavior does not necessarily follow the global or average behavior. As the measurement studies face difficulties to establish the link between a trace and an individual user due to both technical and privacy issues, we propose individual models of users inspired from fictional characters who represent different kinds of consistent behaviors. In this paper, we define such models with a non-homogenous semi-markovian process and give validation results that show that our model is consistent with global models in terms of population and session duration.
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Title: A Survey and Synthesis of User Behavior Measurements in P2P Streaming Systems

Section 1: INTRODUCTION
Description 1: Introduce the topic and importance of understanding user behavior in P2P streaming systems.

Section 2: RELATED WORK
Description 2: Summarize existing surveys and studies related to P2P streaming protocols and user behavior.

Section 3: VIDEO STREAMING ARCHITECTURES
Description 3: Provide a brief overview of video streaming architectures, including client/server, IP multicast, and P2P systems.

Section 4: USER BEHAVIOR AND ITS MEASUREMENT
Description 4: Discuss the distinctions between live streaming and VoD in P2P systems and present an overview of user behavior measurements.

Section 5: SYNTHESIS OF MEASUREMENTS OVER LIVE STREAMING SYSTEMS
Description 5: Perform a synthesis of user behavior measurements over live streaming systems, analyzing and comparing user behavior metrics and their relationships.

Section 6: SYNTHESIS OF MEASUREMENTS OVER VOD SYSTEMS
Description 6: Discuss the observations and synthesis of user behavior measurements over VoD streaming systems, comparing metrics and their relationships with environments and network performance parameters.

Section 7: CONCLUSIONS AND FUTURE PERSPECTIVES
Description 7: Summarize the key findings from the survey, highlight the implications, and suggest directions for future research.