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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

A proactive low-overhead file replication scheme for structured P2P content delivery networks

File replication is a widely used technique for high performance in peer-to-peer content delivery networks. A file replication technique should be efficient and at the same time facilitates efficient file consistency maintenance. However, most traditional methods do not consider nodes’ available capacity and physical location in file replication, leading to high overhead for both file replication and consistency maintenance. This paper presents a proactive low-overhead file replication scheme, namely Plover. By making file replicas among physically close nodes based on nodes’ available capacities, Plover not only achieves high efficiency in file replication but also supports low-cost and timely consistency maintenance. It also includes an efficient file query redirection algorithm for load balancing between replica nodes. Theoretical analysis and simulation results demonstrate the effectiveness of Plover in comparison with other file replication schemes. It dramatically reduces the overhead of both file replication and consistency maintenance compared to other schemes. In addition, it yields significant improvements in reduction of overloaded nodes.     

基于P2P覆盖树网络的流媒体传输技术优化研究

PeerCast是一个基于P2P网络的流媒体传输系统,各节点被组织成树状来进行数据的分发.但没有一个有效的机制来维护树的平衡和保证所选取的父节点是最佳的节点.在此基础上,对该系统进行优化,在媒体数据包上加一个字节用来标识当前节点与根节点的距离,并对节点间响应消息进行优化.实验结果表明,这些优化措施能够有效的维护树的平衡和降底数据传输时延.     

A structured approach for cooperative query answering

This paper proposes the use of a type abstraction hierarchy as a framework for deriving cooperative query answers. The type abstraction hierarchy integrates the abstraction view with the subsumption (is-a) and composition (part-of) views of a type hierarchy. Such a framework provides multilevel object representation, which is an important aspect of cooperative query answering. The concept of pattern that specifies one or more conditions on an object is also proposed. Patterns have smaller granularity than types, and thus provide more specific semantic information. Cooperative query answering consists of query relaxation, generalization, specialization, and association on patterns. Query relaxation can be explicitly specified by the user or implicitly performed by the system. The implicit and explicit relaxations can also be combined and performed interactively by both the system and the user. CSQL, an extension of SQL for cooperative query answering, is also proposed. Preliminary experimental results reveal that the proposed type abstraction hierarchy provides an organized structure representing concepts at different knowledge levels in various domains, and provides a systematic and efficient method for cooperative query answering     

A structured approach for VLSI circuit design

The authors review the research done on a structured, symbol-based IC design method called path programmable logic (PPL). They explain the logic partitioning strategy on which PPL is based. Compared to full-custom design methods, the PPL methods permits an order of magnitude reduction in design time. In most cases, the density of the circuits designed using the PPL method approaches or surpasses that of the practical full-custom designs. Compared to semicustom design techniques such as standard cells and gate arrays, PPL reduces the design time by a factor of three while improving the densities by a factor of two to three     

Extending OAI-PMH over structured P2P networks for digital preservation

Open archives initiative (OAI) allows both libraries and museums create and share their own low-cost digital libraries (DL). OAI DL are based on OAI-PMH protocol which, although is consolidated as a pattern for disseminating metadata, does not rely on either digital preservation and availability of content, essential requirements in this type of system. Building new mechanisms that guarantee improvements, at no or low cost increases, becomes a great challenge. This article proposes a distributed archiving system based on a P2P network, that allows OAI-based libraries to replicate digital objects to ensure their reliability and availability. The proposed system keeps and extends the current OAI-PMH protocol characteristics and is designed as a set of OAI repositories, where each repository has an independent fail probability assigned to it. Items are inserted with a reliability that is satisfied by replicating them in subsets of repositories. Communication between the nodes (repositories) of the network is organized in a distributed hash table and multiple hash functions are used to select repositories that keep the replicas of each stored item. The OAI characteristics combined with a structured P2P digital preservation system allow the construction of a reliable and totally distributed digital library. The archiving system has been evaluated through experiments in a real environment and the OAI-PMH extension validated by the implementation of a proof-of-principle prototype.     

A structured P2P network based on the small world phenomenon

In this paper, we propose a new structured P2P overlay network, named SW-Uinta(small-world). In order to reduce the routing latency, we firstly construct the Uinta network in which both physical characteristics of network and data semantic are considered. Furthermore, based on Uinta, a nondeterministic caching strategy is employed to allow for poly-logarithmic search time while having only a constant cache size. Compared with the deterministic caching strategy proposed by previous P2P systems, the nondeterministic caching strategy can reduce communication overhead for maintaining the routing cache table. Cache entries in the cache table of peer nodes can be updated by subsequent queries rather than only by running stabilization periodically. In the following, a novel cache replacement scheme, named the SW cache replacement scheme, is used to improve lookup performance, which has proved to satisfy the small-world principle. So we call this network SW-Uinta(small-world). After that, according to the theoretical analysis, it can be proved that SW-Uinta(small-world) can get O((log ² N)/k) search time with O(k) cache size. Lastly, the performance of SW-Uinta(small-world) is compared with those of other structured P2P networks such as Chord and Uinta. It shows that SW-Uinta(small-world) can achieve improved object lookup performance and reduce maintenance cost.