MANET adaptive structured P2P overlay

This paper presents an efficient structured P2P overlay over MANET which better matches to the physical network in term of routing. This feature is achieved by locally building up the minimum-spanning tree (MST) at each peer using the information of the peer’s logical neighbors which are either directly connected (1-hop) or 2-hops away. Using this interconnection structure among the peers, we design a new algorithm to distribute the contents information in the overlay by partitioning the identifier (ID) space among the peers. In this algorithm, each peer maintains a disjoint portion of the ID space. The ID space at a peer may be non-contiguous and each contiguous part is consecutive to the ID space of its directly connected neighbor peers. To route the file-lookup query, each peer builds up a binary search tree (BST) using the knowledge of the ID space of itself and of its directly connected neighbor peers. Simulation results show that our approach outperforms the existing approaches in term of routing overhead, average file-discovery delay, false-negative ratio and average path-stretch value.     

一种网络敏感的结构化小世界P2P覆盖网络*

近年来人们对结构化P2P覆盖网络进行了大量的研究,在结构化P2P网络的构建中,下层的网络拓扑结构并没有得到考虑,因此在端到端的通信中,尽管覆盖网上所反映出路径跳数很少,但实际的延迟却会很大。针对此问题,结合小世界理论提出一种网络敏感的新P2P覆盖网络,使实际网络中邻近的节点能聚集到同一簇中,并利用小世界网络平均距离小和大簇系数特性进行路由选择和拥塞控制。仿真实验表明,与经典的P2P覆盖网络相比,该网络具有更高的查询效率。     

Balance-Peer:负载均衡的结构化P2P模型

为了有效实现结构化P2P系统中数据均衡分布,借鉴并行数据库中数据划分的基本思想,通过在节点加入和数据加入时的存储均衡算法实现大数据量在系统中存储均衡,使得系统存储差异系数大大降低.设计了一个使用数据划分的结构化P2P模型Balance-Peer.在不需要全局信息的情况下,实现动态数据划分方法.实验结果表明了该存储均衡策略是有效的.     

利用结构化对等网络构造计算资源共享平台

设计和构建了一个基于结构化对等网络的计算资源共享平台DHT-CRSP。它可以把因特网上用户提交的科学计算作业高效地映射到平台中合适的工作节点上运行,通过容错和安全机制,能保证系统的可靠性和正确性。描述了DHT-CRSP中支持的两种分布式哈希表：Chord协议节点树和CAN协议空间区域;分析了DHT-CRSP中高效的资源匹配算法。通过构建评测环境,运行各种负载与作业场景下的结果表明,DHT-CRSP系统可以获得好的负载均衡性能、低的资源匹配代价,它提供了一种构建高性能的桌面网格平台的新思路。     

A self-similar super-peer overlay construction scheme for super large-scale P2P applications

Unstructured peer-to-peer (P2P) overlay networks with two-layer hierarchy, comprising an upper layer of super-peers and an underlying layer of ordinary peers, are used to improve the performance of large-scale P2P applications like content distribution and storage. In order to deal with continuous growth of participating peers, a scalable and efficient super-peer overlay topology is essential. However, there is relatively little research conducted on constructing such super-peer overlay topology. In the existed solutions, the number of connections required to be maintained by a super-peer is in direct proportion to the total number of super-peers. For super large-scale P2P applications, i.e. the number of participating peer is over 1,000,000, these solutions are not scalable and impractical. Therefore, in this paper, we propose a scalable hierarchical unstructured P2P system in which a self-similar square network graph (SSNG) is proposed to construct and maintain the super-peer overlay topology adaptively. The SSNG topology is a constant-degree topology in which each node maintains a constant number of neighbor nodes. Moreover, a simple and efficient message forwarding algorithm is presented to ensure each super-peer to receive just one flooding message. The analytical results showed that the proposed SSNG-based overlay is more scalable and efficient than the perfect difference graph (PDG)-based overlay proposed in the literature.     

一种分层分簇的P2P流媒体覆盖网络模型

提出一种新型的分层分簇结构的P2P覆盖网络模型HCPON。该模型根据能力对节点分层处理,分簇聚合,分别应用不同方案优化覆盖网络结构,兼顾了节点的能力差异性和位置特性。仿真实验表明,该模型具有很好的可扩展性和鲁棒性,能够满足大规模流媒体服务需求。     

Service-based P2P overlay network for collaborative problem solving

This paper describes a service-based P2P overlay network architecture to support a collaborative environment for solving complex business processes over the network. In the proposed architecture, autonomic service providers corresponding to various activities that occur in the processes reside on the overlay network and are discovered dynamically during the execution of the process. To consummate a specific process, a set of services that map into the business process are federated together and executed in a choreographed sequence. All services have standardized interfaces and this allows any service to be seamlessly replaced with another service without affecting the performance of the federation. The paper presents two cases of application of this architecture, namely, business-to-business collaboration in an engineering environment (General Electric) and multiparty financial transactions (mortgage).     

SyMon: A practical approach to defend large structured P2P systems against Sybil Attack

Sybil attack is one of the most challenging problems that plague current decentralized Peer-to-Peer(P2P) systems. In Sybil attack, a single malicious user creates multiple peer identities known as sybils. These sybils are employed to target honest peers and hence subvert the system. In this paper, we describe a novel solution that enables all honest peers to protect themselves from sybils with high probability in large structured P2P systems. In our proposed sybil defense system, we associate every peer with another non-sybil peer known as SyMon. A given peer’s SyMon is chosen dynamically such that the chances of both of them being sybils are very low. The chosen SyMon is entrusted with the responsibility of moderating the transactions involving the given peer and hence makes it almost impossible for sybils to compromise the system. We show the effectiveness of our proposed system in defending against Sybil attack both analytically and experimentally. In addition to this, we explore the feasibility of our proposed solution in two P2P applications: reputation systems for P2P based file sharing applications and P2P applications susceptible to Denial-of-Service(DOS) attack, systems known to be highly vulnerable to Sybil attack. In each of our case studies, we discuss possible ways in which our solution can be employed to defend the system against Sybil attack.     

结构化P2P自适应混合负载均衡策略

本文在深入研究已有负载均衡策略的基础上,提出了一种建立在结构化P2P上基于Chord的自适应高可用性混合负载均衡策略--RGP(Replication and Gossip Policy).该策略结合了流言传播与动态副本策略,并将负载失衡分为轻负载和重负载区分对待,以提高结构化P2P网络的性能.     

Enhancing P2P overlay network architecture for live multimedia streaming

The number of live multimedia streaming applications is increasing, explaining the use of many overlay network topologies. Application-layer multicast (ALM) that it is a feasible alternative to multimedia stream has attracted considerable attention. However, a serious problem of ALM is that the multicast tree may be fragile, and peer failure causes tree partitions. This work presents a novel Hierarchical Ring Tree (HRT) architecture for Peer-to-Peer (P2P) live multimedia streaming. The proposed architecture combines ring-based and tree-based structures in a robust, scalable, reliable and resilient structure that can be used practically as an ALM topology. When peers enter or leave the system, the topology can be recovered rapidly such that live multimedia stream can be delivered smoothly with a low latency. The proposed HRT topology is maintained efficiently without splitting or merging trees. The performance of the proposed architecture and algorithms is evaluated experimentally. Experimental results indicate that the proposed topology can be used in a high-churn P2P network with a small delay. Simulation and experiment results reveal that the proposed architecture has a lower overhead than the ZIGZAG approach when handling peers’ joining or leaving, exhibits faster recovery, better quality-of-service during streaming, and a more robust topology, even with an extremely high number of peers joining/leaving.     

面向P2P网络的渐进式三维场景更新策略

近年来网上大规模虚拟环境实时漫游已经成为WebGIS的新兴研究领域。为缓解用户终端极其有限的存储空间与海量场景之间的矛盾,设计了一种面向对等网的新型渐进式场景更新策略(PSRM)。在剔除场景前,节点通过分别计算场景文件对自身视点的“视觉保留度”、场景文件对自身兴趣区域(AOI)邻居的“潜在贡献度”及“物体重用度”,综合确定需要被剔除的场景,并按照逐渐降低场景分辨率的策略剔除旧有场景数据。仿真显示,PSRM在下载饱满度、基网格下载饱满度两个衡量漫游效果的重要指标上较现有系统有明显提升,同时能大幅降低漫游过程中的服务器端负载。     

A multi-timescale cross-layer approach for wireless ad hoc networks

Conventionally, cross-layer designs with same timescale updates can work well; however, there is a difference in layers’ timescales and each layer normally operates at its corresponding timescale when implemented in real systems. To respect this issue, in this article, we introduce a multi-timescale cross-layer design along with three sets of constraints: congestion control, link delay, and power control and with the objective of maximizing the overall utility and minimizing the total link delay and power consumption. The proposed procedure can be implemented in a distributed fashion, which not only guarantees truly optimal solutions to the underlying problem, but also adheres to the natural timescale difference among layers. Finally, the numerical results further solidify the efficacies of our proposal compared to the current frameworks.     

A cross-layer approach for multiuser multiplexing on IP mobility

In general, content distribution and multicasting can be implemented from proxies and gateways in the network on a static host in wired/wireless network environments. However, if an end point host moves to different wireless access networks, it will have a problem in many situations. For example, consideration of contents like the level of required service quality for network search, handoff, connection and call time, and caching and load balancing is necessary. Unlike previous studies, this article analyzes additional costs related to Fast Handover and compares the performance of group of pictures and data transmission delay time. For this, first, the total additional cost was divided into signaling cost and packet transmission cost, and results of the comparison calculated for video data transmission delay time and traffic overhead are presented. This article proposes service quality improvement methods by acquiring multiuser channel state information for multicast video-streaming transmission with a method implemented between network layers. Channel state information of each user in the multicast group is used as information for the transmission of multicast packets. Thus, through simulation like real-time traffic, the optimum traffic transmission state is maintained. As a result of the simulation, we found that video-streaming service performance for multicast users improved by applying the approach method between layers. This article proposes optimization methods of a cross-layered approach for wireless network multimedia communication systems and video-streaming application services.     

A novel state cache scheme in structured P2P systems

Large-scale P2P systems typically have hundreds of thousands of peers that involve frequent dynamic activities. Current structured overlays do not identify well the rhythm in the dynamic activities, thus resulting in high maintenance overhead. In this paper, we present a new state cache system, called SCS, that solves the problem by exploiting the access patterns of dynamic activities in P2P systems. SCS partitions the whole P2P network into clusters and dynamically chooses a “super” node in each cluster to selectively record and maintain the routing information for departed nodes most likely to arrive back in the near future. The cached routing information enables SCS to simplify self-organization, reduce system maintenance overhead and provide high quality routing service. The experimental results show that SCS reduces the maintenance overhead by up to 66% while delivering much better routing performance, as compared to current structured P2P systems.     

无标度异构网络中的层次化P2P覆盖网设计

针对P2P应用系统中存在的负载不均衡,拓扑不匹配等问题,提出在无标度网络中的节点上分别实现路由和服务索引维护这两种功能的覆盖网设计思想,以Chord为例设计节点成簇和成环算法,实现三层覆盖网体系和二维地址空间结构,并提出节点负载分析模型。仿真结果表明,相比以往2层的以Chord为中心的覆盖网,新提出的覆盖网在查询路径长度、负载、查询成功率等多个性能指标上都有很大的优化。     

A graph-theoretic approach to fault detection and isolation for structured bilinear systems

In this paper, using a graph-theoretic approach, we address some issues related to the fault detection and isolation for structured bilinear systems. Considering a structured bilinear system submitted to faults and disturbances, we give necessary and sufficient conditions to the solvability of the so-called bilinear fundamental problem of residual generation. We also treat the cases where the system is submitted to multiple failures occurring simultaneously or only one at a time. One of the main advantages of the proposed analysis tool is that all the given conditions are easy to check because they deal with finding paths in a digraph. This makes our approach well suited to studying large scale systems.     

一种卫星移动通信中的L/P跨层设计

针对卫星移动信道,提出了一种基于链路层(Link Layer)的混合自动请求重传(HARQ)技术联合物理层(Physical Layer)自适应编码调制(AMC)技术的L/P跨层设计;在Nakagami-m信道模型中验证其性能,并与非跨层设计结果作了对比。理论分析及仿真比较结果表明,这种跨层设计可以综合有效地优化卫星移动通信性能。     

A scalable P2P overlay based on arrangement graph with minimized overhead

With innovations in the Internet, it is becoming increasingly relied upon. In the last decade, research on peer-to-peer (P2P) technology has become even more popular. As more people use P2P systems, the scalability and flexibility of the systems must be considered. In this study, an arrangement graph is used to form a P2P overlay, the Arrangement-Graph Overlay (AGO), to reduce system overhead and bind routing hops. The proposed AGO utilizes the properties of the arrangement graph, i.e., that each node has a unique ID and IDs between adjacent nodes differ by only one digit, to form the overlay network and develop a routing algorithm. The routing hops of the proposed AGO system can be bound within a certain number because of the diameter of the arrangement graph. Experimental results show that the proposed AGO system can greatly reduce system overhead and perform routing in a constant number of hops, even in a large-scale network environment. The experimental results also show that the AGO system consumes less bandwidth, which is an important consideration in P2P systems.     

Receiving-peer-driven multi-video-source scheduling algorithms in mobile P2P overlay networks

This paper proposes two algorithms for multi-video-source in a new mobile P2P architecture for streaming media systems. One is serial, and the other is parallel. When the service peer set providing expected QoS is not empty, the former is called, otherwise the latter is called. The former triggers the video source change event, re-selects a video source, and synchronizes the multi-video-source by the time model of the streaming sequence when QoS is degraded. The latter allows the multiple video sources to concurrently send the data to the receiving peer according to the assigned transmission. Compared to the existing papers, the contribution of this paper is fourfold: (1) the serial and parallel scheduling algorithms, correctly switched according to the actual situation, are firstly proposed; (2) the mobile feature of peers are firstly considered and validated; (3) the client nodes have better and smoother video quality; (4) our algorithms have shorter run time, which is a crucial factor for an on-line system.