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In order to provide live streaming over the global Internet, a content provider often deploys an overlay network consisting of distributed proxies placed close to user pools. Streaming of multi-Mbps video over such an overlay is challenging because of bandwidth bottlenecks in paths. To effectively overcome these bottlenecks, we consider employing proxy helpers in the overlay to provide rich path diversity. The helpers do not have any attached users, and hence may forward partial video streams (or not at all) if necessary. In this way, the helpers serve as stepping stones to supply full streams to the servers. The issue is how to involve the helpers in the overlay to achieve low streaming delay meeting a certain high streaming bitrate requirement. To address the issue, we first formulate the problem which captures various delay and bandwidth components, and show that it is NP-hard. We then propose an efficient algorithm called Stepping-Stones (SS) which can be efficiently implemented in a controller. Given the encouraging simulation results, we develop a novel streaming testbed for SS and explore, through sets of Internet experiments, the effectiveness of helpers to achieve high bitrate (multi-Mbps) global live streaming. In our experiments, proxies are deployed with a reasonably wide global footprint. We collect more than a hundred hours of streaming traces with bitrate ranging from 500kbps to a few Mbps. Our experimental data validates that helpers indeed play an important role in achieving high bitrate in today's Internet. Global multi-Mbps streaming is possible due to their multihop and multipath advantages. Our experimental trials and data also provide valuable insights on the design of a global push-based streaming network. There are strong benefits of using proxy helpers to achieve high bitrate and low delay. [ABSTRACT FROM AUTHOR]

IPTV services deployed nowadays often consist of both live TV and Video-on-Demand (VoD), offered by the same service provider to the same pool of users over the same managed network. Understanding user behaviors in such a setting is hence an important step for system modelling and optimization. Previous studies on user behavior on video services were on either live TV or VoD. For the first time, we conduct an in-depth large-scale behavior study for IPTV users offering simultaneously live TV and VoD choices at the same time. Our data is from the largest IPTV service provider in China, offering hundreds of live channels and hundreds of thousands of VoD files, with traces covering more than 1.9 million users over a period of 5 months. This large dataset provides us a unique opportunity to cross-compare user viewing behaviors for these services on the same platform, and sheds valuable insights on how users interact with such a simultaneous system. Our results lead to new understanding on IPTV user behaviors which have strong implications on system design. For example, we find that the average holding time for VoD is significantly longer than live TV. live TV users tend to surf more. However, if such channel surfing is discounted, the holding times of both services are not much different. While users in VoD tend to view HD longer, channel popularity for live TV is much less dependent on its video quality. In contrast to some popular assumptions on user interactivity, the transitions among live TV, VoD, and offline modes are far from a Markov model. [ABSTRACT FROM AUTHOR]

Many peer-to-peer systems assume that peers are cooperative to share and relay data. But in the open environment of the Internet, there may be uncooperative malicious peers. To detect malicious peers or reward well behaved ones, a reputation system is often used. In this article we give an overview of P2P reputation systems and investigate two fundamental issues in the design: reputation estimation and query. We classify the state-of-the-art approaches into several categories and study representative examples in each category. We also qualitatively compare them and outline open issues for future research. [ABSTRACT FROM AUTHOR]

Since the quality of compressed video is vulnerable to errors, video transmission over unreliable Internet is very challenging today. Multi-hypothesis motion-compensated prediction (MHMCP) has been shown to have error resilience capability for video transmission, where each macroblock is predicted by a linear combination of multiple signals (hypotheses). B picture prediction is a special case of MHMCP. In H.264/AVC, the prediction of B pictures is generalized such that both of the two predictions can be selected from the past pictures or from the subsequent pictures. The multiple reference picture framework in H.264/AVC also allows previously decoded B pictures to be used as references for B picture coding. In this paper, we will discuss the error resilience characteristics of the generalized B pictures in H.264/AVC. Three prediction patterns of B pictures are analyzed in terms of their error-suppressing abilities. Both theoretical models (picture level error propagation) and simulation results are given for the comparison. [ABSTRACT FROM AUTHOR]

IP multicast and overlay multicast have been proposed for one-to-many data delivery over the Internet. Compared to overlay multicast, IP multicast is less deployed but can achieve higher delivery efficiency. Researchers hence study how to combine IP multicast with overlay multicast in order to achieve both high deployability and high delivery efficiency. This combination is called island multicast. In this article we present a comprehensive survey of recent research on island multicast. We investigate the general architecture and key components of island multicast. We then discuss the core issue in island multicast: how to set up delivery connections across multiple multicast domains. We finally discuss open issues for future research. [ABSTRACT FROM AUTHOR]

The article focuses on the deployment issues of Scalable Island Multicast (SIM), a network that incorporates Internet Protocol (IP) into peer-to-peer (P2P) overlay delivery. It states that SIM was deployed on the Home Media Center Platform of the Hong Kong Applied Science and Technology Research Institute using a set-top box (STB). Results show that SIM provides efficient video-compression algorithm compared to H.263 standard precursor, allows packet retrieval and decoding from networks, and produces television (TV) signals to TV sets through audiovideo output. Furthermore, relay delay penalty (RDP), link stress, and resource usage are the metrics used to evaluate transit-stub topologies.

Provisioning random access functions in peer-to-peer on-demand video streaming is challenging, due to not only the asynchronous user interactivity but also the unpredictability of group dynamics. In this paper, we propose VMesh, a distributed peer-to-peer video-on-demand (VoD) streaming scheme which efficiently supports random seeking functionality. in VMesh, videos are divided into segments and stored at peers' local storage in a distributed manner. An overlay mesh is built upon peers to support random forward/backward seek, pause and restart during playback. Our scheme takes advantage of the large aggregate storage capacity of peers to improve the segment supply so as to support efficient interactive commands in a scalable manner. Unlike previous work based on "cache-and-relay" mechanism, in our scheme, user interactivity such as random seeking performed by a peer does not break the connections between it and its children, and hence our scheme achieves better playback continuity. Through simulation, we show that our system achieves low startup and seeking latency under random user interactivity and peer join/leave which is a crucial requirement in an interactive VoD system. [ABSTRACT FROM AUTHOR]

The article discusses Internet multimedia streaming applications. Large-scale multimedia streaming over the Internet requires a large amount of server and network resources. Traditional client-server approaches allocate a dedicated stream from the server for each client request, but this approach is expensive and doesn't scale well. The authors state that by using end hosts' huge bandwidth and computational capacity, peer-to-peer technologies support media streaming applications' development. Locating supplying peers and content delivery path maintenance remain as two major challenges in this area. INSET: Related Solutions in Media Streaming.

In traditional mobile streaming networks such as 3G cellular networks, all users pull streams from a server. Such pull model leads to high streaming cost and problem in system scalability. In this paper, we propose and investigate a fully distributed, scalable, and cost-effective protocol to distribute multimedia content to mobiles in a peer-to-peer manner. Our protocol, termed Collaborative Streaming among Mobiles (COSMOS), makes use of broadcasting and data sharing to achieve high performance (in terms of delay, cost fairness, stream continuity, etc.). In COSMOS, only a few peers pull video descriptions from base stations. Using a free broadcast channel (such as Wi-Fi and Bluetooth), they share the streams to nearby neighbors. As a result, COSMOS greatly reduces the streaming cost and cellular bandwidth requirement. Furthermore, as video streams are supplied by multiple peers, COSMOS is robust to peer failure. Since broadcasting is used to distribute video data, COSMOS is highly scalable to large number of users. In COSMOS, peers autonomously determine whether to broadcast packets or not in order to efficiently use of the channel bandwidth. By taking turns to pull descriptions, peers can effectively share, and hence substantially reduce, streaming cost. As broadcast scope is small and peers can often obtain a number of streams from its neighbors, COSMOS achieves low delay and excellent stream continuity. [ABSTRACT FROM AUTHOR]

The delivery of quality video service often requires high bandwidth with low delay or cost in network transmission. Current routing protocols such as those used in the Internet are mainly based on the single-path approach (e.g., the shortest-path routing). This approach cannot meet the end-to-end bandwidth requirement when the video is streamed over bandwidth-limited networks. In order to overcome this limitation, we propose multipath routing, where the video takes multiple paths to reach its destination(s), thereby increasing the aggregate throughput. We consider both unicast (point-to-point) and multicast scenarios. For unicast, we present an efficient multipath heuristic (of complexity O(|V|³)), which achieves high bandwidth with low delay. Given a set of path lengths, we then present and prove a simple data scheduling algorithm as implemented at the server, which achieves the theoretical minimum end-to-end delay. For a network with unit-capacity links, the algorithm, when combined with disjoint-path routing, offers an exact and efficient solution to meet a bandwidth requirement with minimum delay. For multicast, we study the construction of multiple trees for layered video to satisfy the user bandwidth requirements. We propose two efficient heuristics on how such trees can be constructed so as to minimize the cost of their aggregation subject to a delay constraint. [ABSTRACT FROM AUTHOR]

In recent years, there has been an increasing interest to deliver multimedia services over wireless ad hoc networks. Due to the existence of hidden terminal and absence of central control, the medium access control protocol as used in the ad hoc networks may lead to channel capture, where some flows monopolize the channel while others suffer from starvation. As a consequence, the system throughput and fairness are greatly degraded. After showing that static power control leads to channel capture, we propose and study a distributed dynamic power control scheme termed "power adaptation for starvation avoidance" (PASA), which dynamically adjusts the transmission power of a node so as to avoid starvation. PASA is shown to be effective in breaking channel captures, hence improving short-term fairness among contending flows. It is simple, fully autonomous and requires no communication overhead. Via extensive simulations, we show that our power control algorithm achieves much better fairness without compromising system throughput through better spatial reuse. Our experiments with video sequences transmitting over different network topologies show that PASA achieves much better video quality with lower start-up delay and buffer requirement. [ABSTRACT FROM AUTHOR]

In order to cost-effectively accommodate a large number of titles in a video system, a hierarchical storage system can be used. In this system, not-so-popular video files are stored in a tertiary level such as a disk/tape library. These files are transferred, or "staged," to a secondary level composed of magnetic disks before being streamed to the users. This system overcomes the current limitations in using disk/tape libraries to stream videos and resolves the bandwidth difference between staging and streaming. In this paper, we present, via analysis, a model of the system and determine the minimum storage and bandwidth required, at each level, to meet a given user delay goal. We also analyze a number of system operations pertaining to whether or not a file is played while it is being staged (i.e., stage-streaming) and whether or not the displayed segments are deleted (i.e., trail-deletion). We show that stagestreaming and trail-deletion can achieve substantially lower bandwidth and storage requirements. In order to further increase the streaming and storage scalability, a distributed storage system can be used where multiple local servers are put close to user pools and get their files from one of the libraries through a network. We extend the models developed to such a system and specify the resource requirements to meet a given delay goal. [ABSTRACT FROM AUTHOR]

Discusses a study which proposed a distributed servers approach to minimize the overall system bandwidth by splitting the user pool into multiple groups each served by a server. Step taken in order to offer backward and forward secrecy for multicast applications; Advantages of the approach; Efficiency of the multicast technique.

The article discusses various reports published within the issue including "Will IPTV Ride the Peer-to-Peer Stream?," by Gustavo Marfia and "Experience on Deploying P2P Networks for LargeScale Live Video Streaming Service," by Yun Tang, Qian Zhang and Shiqiang Yang.