Upstream Peers Research Articles

An Efficient Hybrid Push-Pull Based Protocol for VOD In Peerto-Peer network

Video-on-Demand is a service where movies are delivered to distributed users with low delay and free interactivity. The traditional client-server architecture experiences scalability issues to provide video streaming services. Peer-to-Peer (P2P) techniques for video on demand (VOD) have been shown to be a good enhancement to the traditional client/server methods when trying to reduce costs, increase robustness and solve the scalability issues. Various challenges arise when building a resilient P2P video on demand systems, such as long waiting time to receive the video segments and the quality of service. A new proposed data exchange schema is called Efficient Hybrid Push-Pull based Protocol (EHP3) can reduce the initial playback delay and improve the quality of service. The downstream peer has to accelerate the downloading process of the urgent segments, i.e. those missing segments which are near their playback time. The range of the urgent segments is referred to as the priority region. The upstream peers give a strict priority to segments within the priority region. If the downstream peer has sufficient download bandwidth, it should be able to completely receive these urgent segments before playback time. If there are no missing segments in the priority region, the downstream peer uses the pull protocol to download the missing segments which are outside the priority region. The simulation result shows that the proposed data exchange schema (EHP3) can reduce the initial play back delay and reduce the burden on the server side by increasing the number of caching segments in the playback buffer. Moreover, the proposed schema improves the quality of service by reducing the number of skipped segments during the playback.

Centrality-Based Network Coder Placement for Peer-To-Peer Content Distribution

Network coding has been shown to achieve optimal multicast throughput, yet at an expensive computation cost: every node in the network has to code. Interested in minimizing resource consumption of network coding while maintaining its performance, in this paper, we propose a practical network coder placement algorithm which achieves comparable content distribution time as network coding, and at the same time, substantially reduces the number of network coders compared to a full network coding solution in which all peers have to encode, i.e. become encoders. Our algorithm is derived from two key elements. First, it is based on the insight that coding at upstream peers eliminates information duplication to downstream peers, which results in efficient content distribution. Second, our placement strategy exploits centrality characteristics of the network topology to quickly determine key positions to place encoders. Performance evaluation using various topology and algorithm parameters confirms the effectiveness of our proposed method.

An Efficient P2P Content Distribution System Based on Altruistic Demand and Recoding Dissemination

Peer-to-peer (P2P) content distribution systems based on random linear combination coding schemes outperform traditional block forwarding and source coding systems but have large storage requirements and high computation and communication overheads. To resolve this problem, this paper presents an efficient and scalable P2P content dissemination system based on novel altruistic demand and recoding dissemination mechanisms. In the proposed approach, the shared-content file is segmented and encoded using Reed-Solomon code at a seed. Downstream peers wishing to obtain the file utilize an altruistic demand mechanism to issue demand requests for coded blocks which are useful not only to themselves but also to their neighbors. Upon receiving these requests, the upstream peers utilize a recoding dissemination mechanism to provide the downstream peers with either an existing useful coded block or a new coded block produced using a Lagrange polynomial interpolation method. The two mechanisms rapidly increase the diversity of the coded blocks within the network and therefore provide an effective solution to the missing last block problem. In addition, it is shown that the proposed content distribution system demonstrates a substantial improvement over P2P systems based on random linear combination coding in terms of a lower storage requirement, reduced computation and communication costs, and an improved download efficiency.

On Game Theoretic Peer Selection for Resilient Peer-to-Peer Media Streaming

Peer-to-peer (P2P) media streaming quickly emerges as an important application over the Internet. A plethora of approaches have been suggested and implemented to support P2P media streaming. In our study, we first classified existing approaches and studied their characteristics by looking at three important quantities: number of upstream peers (parents), number of downstream peers (children), and average number of links per peer. In existing approaches, peers are assigned with a fixed number of parents without regard to their contributions, measured by the amount of outgoing bandwidths. Obviously, this is an undesirable arrangement as it leads to highly inefficient use of the P2P links. This observation motivates us to model the peer selection process as a cooperative game among peers. This results in a novel peer selection protocol such that the number of upstream peers of a peer is related to its outgoing bandwidth. Specifically, peers with larger outgoing bandwidth are given more parents, which make them less vulnerable to peer dynamics. Simulation results show that the proposed protocol improves delivery ratio using similar number of links per peer, comparing with existing approaches under a wide range of system parameters.

Dynamic Bandwidth Auctions in Multioverlay P2P Streaming with Network Coding

In peer-to-peer (P2P) live streaming applications such as IPTV, it is natural to accommodate multiple coexisting streaming overlays, corresponding to channels of programming. In the case of multiple overlays, it is a challenging task to design an appropriate bandwidth allocation protocol, such that these overlays efficiently share the available upload bandwidth on peers, media content is efficiently distributed to achieve the required streaming rate, as well as the streaming costs are minimized. In this paper, we seek to design simple, effective, and decentralized strategies to resolve conflicts among coexisting streaming overlays in their bandwidth competition and combine such strategies with network-coding-based media distribution to achieve efficient multioverlay streaming. Since such strategies of conflict are game theoretic in nature, we characterize them as a decentralized collection of dynamic auction games, in which downstream peers bid for upload bandwidth at the upstream peers for the delivery of coded media blocks. With extensive theoretical analysis and performance evaluation, we show that these local games converge to an optimal topology for each overlay in realistic asynchronous environments. Together with network-coding-based media dissemination, these streaming overlays adapt to peer dynamics, fairly share peer upload bandwidth to achieve satisfactory streaming rates, and can be prioritized.

Outreach: peer-to-peer topology construction towards minimized server bandwidth costs

On-demand and live multimedia streaming applications (such as Internet TV) are well known to utilize a significant amount of bandwidth from media streaming servers, especially as the number of participating peers in the streaming session scales up. To scale to higher bit rates of media streams and larger numbers of participating peers, overlay tree or mesh topologies are typically constructed, such that peers utilize their available upload capacities to alleviate the excessive bandwidth demands on stream servers. Previous works rely on random selections of upstream peers, without optimizing the topologies towards maximized utilization of peer upload bandwidth, and as a result, minimized bandwidth costs on streaming servers. We propose Outreach, a distributed algorithm to construct overlay topologies among participating peers in streaming sessions. The design objective of Outreach is to optimize the quality of overlay topologies towards scalability, with respect to the number of participating peers in the session. To be scalable, Outreach seeks to maximize the utilization of available upload bandwidth on each participating peer, and consequently minimize the total bandwidth costs on streaming servers. With analysis, we show that Outreach constructs topologies such that peers can fully utilize their upload capacities, and present a practical distributed algorithm. With simulation-based comparison studies, we show that Outreach effectively achieves its goals in a high-churn peer-to-peer network with an assortment of peer uplink capacities and link delays.