A Supply-and-Demand Model for On-Demand Streaming in Networked Virtual Environments |
In a large scale networked virtual environment, users may request various multimedia data on-demand in streaming. Although adopting a peer-to-peer (P2P) architecture can make the transmission of on-demand streaming more efficient, most existing research assume that the peers have infinite buffer to cache the entire content and supply the data from there. In this paper, we consider the practical case in which the peers have limited buffer space to cache only a portion of the multimedia content. Due to limited buffer space, peers need effective chunk selection strategies to fetch and discard chunks. We propose a supply-and-demand strategy to estimating the usability of chunks. Peers then select the chunk with a higher usability to fetch and discard useless chunks. Simulation results show that the supply-and-demand strategy selects the chunks accurately and enhances the continuity of playing the video. |
Group-Based Peer-to-Peer 3D Streaming Authentication |
In this paper, we present an authentication scheme for group-based peer-to-peer 3D streaming that takes advantage of secure group communication to reduce computation overheads of authentication. Users of the same interest first form a group, and one of the users is then elected to be the trusted leader, who is to download 3D contents, to verify their authenticity and integrity, and to send group members a checksum value for each 3D content piece via group secure channels. By the encrypted checksum values, a group member can authenticate 3D contents downloaded from any source. Since checksum is cheap to compute, much computation is saved. We have evaluated the computation saving of the proposed scheme for the case of progressive meshes based on the hash chain signature 3D streaming authentication scheme. We have also evaluated the rendering quality when embedding hash chain signatures into the least significant bits (LSBs) of the mesh data to make the signatures imperceptible. |
Evaluation Of The HyperVerse Avatar Management Scheme Based On The Analysis Of Second Life Traces |
Abstract-Massive Multiuser Virtual Environments (MMVEs) and the idea of a global scale 3D Web have grown popular in recent years. While commercial precursors of such environments for the most part rely on centralized client/server architectures, it is commonly accepted that a global scale virtual online world can only be realized in a distributed fashion. Within the HyperVerse project, we have developed and recently presented a two-tier Peer-to-Peer (P2P) architecture that incorporates a loosely structured P2P overlay of user peers and a highly structured overlay of server machines constituting a reliable backbone service. In such a distributed environment, an essential question is how avatars are tracked and interconnected in order to allow mutual rendering and interaction. We have previously proposed a hybrid avatar management scheme that utilizes the backbone service for avatar tracking if necessary, but handles tracking in a P2P fashion when peers can track each other to reduce the backbone load. This paper presents a detailed performance analysis of this algorithm under a realistic scenario, using traces from a large scale MMVE called Second Life. Moreover this paper presents and evaluates an optimization for the hybrid avatar tracking scheme that can be utilized under a weaker condition. |
Measuring the Influence of Active Measurement on Unstructured Peer-to-Peer Network |
We present in this study an attempt to measure the in-fluence of active measurement system on unstructured peer-to-peer (P2P) network. To measure a peer-to-peer (P2P) network, a set of measuring peers along with connections among them are deployed as an active measurement system into the target network. The information gathered by measurement system are further refined into the final measuring results. However, it is still unknown to what extent the measurement system itself influences the final measurement results. The final results will have little information if significant influence is introduced by a measurement system. As an initial study, we investigate in this paper the influence of a measurement system on degree distribution of a P2P network. Theoretical analysis and simulation results suggest an interesting phase-transition phenomena when measurement system increases. In particular, a P2P network mixed with a small active measurement added remains as a scale-free network; however, the mixture P2P network will not remain as scale-free when the size of measurement system exceeds a threshold. We also observed that in this process, the number of measuring peers usually has stronger influence than the number of connections among these peers. These results can serve as a guiding rule to design an active measurement system: briefly speaking, a small but dense active measurement is better than a large but loose measurement system. |
Optimizing Unstructured Peer-to-Peer Overlays with Topology Awareness |
In an unstructured peer-to-peer (P2P) network (e.g.,Gnutella), participating peers choose their neighbors randomly such that the resultant P2P network mismatches its underlying physical network, resulting in the lengthy communication between the peers and redundant network traffics generated in the underlying network. Previous solutions to the topology-mismatch problem in the literature are far from the optimum. In this paper, we propose a novel topology-matching algorithm based on the Metropolis-Hastings method. Through extensive simulations, we show that our proposal constructs an unstructured P2P network where a broadcast message, originated by any node v, reaches any other node u by taking approximately the only physical end-to-end delay between v and u. |
iRank: Supporting Proximity Ranking for Peer-to-Peer Applications |
Proximity ranking according to end-to-end network distances (e.g., Round-Trip Time, RTT) can reveal detailed proximity information, which is important in network management and performance diagnosis in distributed systems. However, to the best of our knowledge, there has been no similar work on this subject in the P2P computing field. We present a distributed rating method iRank, that enables proximity rankings by providing discrete ratings in a distributed manner. It formulates the proximity ranking as a rating problem that faithfully captures the proximity based on noisy distance measurements scalably and practically. The primary challenge in inferring proximity rankings is enforcing distributed ratings with complex rating policies. Our solution is based on reconstructing ratings by decomposing a centralized rating method Maximum Margin Matrix Factorization (MMMF) into independent sub-problems, that can be efficiently solved in a decentralized manner. By relaxing the dependence on infrastructure nodes that are a single point of failure and limit scalability, iRank can gracefully handle network churns. Through real network latency data sets, we demonstrate that iRank can predict ratings with low distortion, which are smaller than 20 percentage worse than the centralized method, in the context of synthetic complex rating policies. |
Anadem: A Hybrid Overlay Network for Content-Based Data Distribution |
As an infrastructure for data distribution, overlay networks have to feature efficient routing and adequate robustness to achieve fast and accurate data distribution in the environment with node churn. Considering that the existing overlay networks mostly focus on single optimization objective and fail to ensure routing efficiency and robustness simultaneously, a hybrid overlay network for content-based data distribution - Anadem is proposed in this paper. Anadem achieves a better compromise between routing efficiency and robustness by combining the inter-cluster multiple structured topologies with the intra-cluster unstructured topologies. Anadem also provides mechanisms for dynamic concurrent cluster creation, cluster departure and load balance to make data distribution more adaptive to the dynamic network environment. Experimental results reveal that compared with existing overlay networks, Anadem can support fast and accurate content-based data distribution even when large amount of nodes fail in the system. |
A Replica Placement Algorithm for Hybrid CDN-P2P Architecture |
The Hybrid CDN-P2P architecture, or HCDN, which combines the complementary advantages of CDN and P2P networks, has been proposed to reduce the deployment cost and to improve the quality of service in file sharing and video streaming applications. A replica placement algorithm (RPA) decides where to replicate the specific data. Existing RPAs for pure CDN do not work efficiently in the HCDN architecture because they do not take into consideration the contribution of the peers at the P2P distribution level. In this article, a heuristic RPA that takes into account the effects of P2P distribution is proposed for HCDN. The performance of our proposed algorithm is evaluated and the impact of some key metrics is analyzed. The experimental result shows the clear performance benefits of our approach. |
A diffusive load balancing scheme for Clustered Peer-to-Peer Systems |
Node clustering is an effective solution for achieving good performance and high reliability for peer-to-peer (P2P) systems. To improve the performance of a clustered P2P system, it is important to balance the service load among the clusters in the system. In this paper, we describe a diffusive load balancing scheme for clustered P2P systems, which dynamically adjusts the size of the clusters, by moving nodes among the clusters, based on their service demands and node resource capacities. Our simulations show that the proposed load balancing scheme significantly improves the performance of a P2P system in terms of balanced available capacity. |
Cowtra: A COntribution Willingness-based Two-phase bandwidth Resource Allocation algorithm in P2P network |
Free-riding phenomenon is overwhelming in nowadays p2p network which causes researchers to investigate and develop many approaches to combat it. However, almost all the studies neglect the role of relative contribution of peers, namely willingness of contribution (WoC) in our paper. The ignorant to the ratio of peer's actually contribution to its physical capability would undoubtedly lead to unfairly resource distribution and discourage many peers, as well as loose their support in long term Therefore, in this paper we present a novel and effective approach Cowtra to address such problem. Our algorithm guarantees that the bandwidth of a source node is distributed properly according to the absolute contribution of the competing peers. Then we adjust the amount of competing peers' received bandwidth by utilizing the WoC in the second phase, such that peers with higher WoC obtain more resource while peers with lower WoC otherwise, Cowtra encourages, if not compel, the heterogeneous peers with different capabilities to actively participate in the contribution of P2P community. At last, simulation results demonstrate the superiority of our algorithm in terms of fairness and efficiency. |
2009 International Workshop on Peer-to-PeerNetworked Virtual Environments
(P2P-NVE2009)
Last modified at 2009/09/24