一种面向工业边缘计算应用的缓存替换算法

工业应用对数据传输的确定性有严格要求,有必要通过合理的缓存策略保障工业边缘网络的实时服务性能保障.首先面向工业边缘计算应用场景阐述了边缘缓存问题模型.然后分析了工业应用中用户请求的动态性特点,结合工业用户请求的特征属性,给出用户请求内容流行度变化的预测方法.在此基础上提出了基于属性特征流行度预测的缓存替换(combing periodic popularity prediction and size caching strategy,PPPS)算法,根据最近周期窗口内主导属性特征的热度预测值,和尺寸参数一起确定缓存内容价值.实验结果表明:与MPC(most-popular content)、贪婪双尺寸(greedy dual size,GDS)、最近最久未使用(least recently used,LRU)、最近最少访问频次(least frequently used,LFU)、先进先出(first in first out,FIFO)这5种经典算法相比,提出的PPPS算法在缓存命中率和平均延迟2种性能指标下,在不同的用户请求模型、内容大小分布、内容种类参数下均取得最优性能,有效提升了边缘缓存的命中率,提高了缓存利用效率,降低了用户请求内容的延迟.     

基于实时拓扑属性的虚拟网络映射算法（英文）

研究目的:基于虚拟网络请求和底层物理网络实时拓扑属性,提出一种高效的两步式虚拟网络映射算法。创新要点:分别利用中介中心性和物理节点相关性对虚拟网络请求和底层物理网络中节点进行重要性评估,在此基础上给出一种两步式映射算法(算法1,2)。研究方法:首先给出中间中心性、接近中心性以及节点相关性计算模型,结合节点本地资源分别提出虚拟网络请求和物理网络中节点排名计算方式。当虚拟网络请求到达后,根据虚拟节点排名,将其映射到拥有足够资源的物理节点中排名最靠前的节点。节点映射完成后,使用K-th最短路径算法进行链路映射。映射过程中采用文献(Yu et al.,2008)中所使用的时间窗口模式进行接入控制。重要结论:利用节点本地资源,针对性分析虚拟网络请求和物理网络实时拓扑属性,提出两步式映射算法。该算法提高请求接受率、开销收益比的同时减少算法映射时间,取得更好的映射效果(图3-10)。     

基于小世界特性的网格资源发现算法

对已有的网格资源发现方法进行分析,提出一种以P2P方式实现的、基于小世界特性的非集中式网格资源发现算法。算法将具有相似兴趣属性的结点组织在一起形成兴趣簇,使得搜索请求尽量在簇内进行传播。仿真测试结果表明,该算法可以很好地减少资源发现的通信开销．并有着较高的搜索成功率。     

p2p网络中一种基于信誉感知的资源发现算法

P2P网络的动态性和匿名性对P2P应用获取成功具有显著的贡献，但同时也造成一些恶意节点在网络中提供不可靠或者欺诈的服务．本文在非结构化P2P网络中引入健壮灵活的信誉机制，提出了基于信誉感知的启发式资源发现算法，确保资源请求节点得到可靠的资源和服务．仿真试验表明，该算法有效的抑制了P2P网络中恶意节点的欺诈行为，降低了系统的消息负载，保证了请求节点获得服务和资源的可靠性和安全性．     

基于兴趣聚类的网格资源发现算法*

为了更有效地解决网格资源的搜索和定位问题,提出一种以P2P形式实现的、基于兴趣聚类的非集中式网格资源发现算法.算法采用被动学习方式,通过用户的访问历史抽取节点的兴趣属性,将节点按照兴趣属性划分为多个簇,资源发现请求在簇内朋友节点之间传播,查找失败后,将请求路由到与其兴趣最相似的其他簇内.仿真测试表明,算法稳定高效,相比传统算法在低开销情况下性能有显著的提高.     

符合动态演变特性的网格资源发现机制研究

近年来人们对如何提高网格资源发现效率做了大量的研究,但却忽略了适应网格资源动态演变特性的重要性.针对这一问题,结合小世界理论的网络特征,提出了一种新的基于P2P分布式结构化的网格资源发现机制.通过计算资源节点间属性相似度的方法,将网格资源分类组织在不同的虚拟组织中,结合P2P技术构建出两层覆盖式资源发现模型,并设计出相应的资源查找算法DSRD (distributed structure grid resource discovery).仿真实验结果表明,DSRD算法既能够适应资源的动态特性,同时又可有效地提高资源发现效率.     

跨数据中心的动态资源联合预留研究

如何有效保障服务质量(Quality of Service,QoS)是网格计算和云计算等网络计算平台面临的核心问题之一,资源可获得性和性能的动态变化使得将多媒体网络的资源提前预留机制直接应用到网络计算平台面临巨大挑战.为此提出了一种跨数据中心的资源联合预留体系架构,引入虚拟资源容器以适应资源的动态性,提出了资源预留协商算法以增加预留请求与资源的匹配率.在东南大学校园云计算平台的实验结果表明,在资源动态变化的网络计算环境中,所提出的体系架构能显著提高预留请求的成功率,且具有更强的稳定性.     

对等网络中基于结点兴趣的资源查找算法

为了提高对等网络中资源查找的效率,根据P2P结点的群聚特性,构建了基于结点兴趣的覆盖网络,并设计了相应的资源查找算法。算法根据查询请求和结点的相似度来决定搜索策略,在簇内查找请求不能被满足时,请求将被发送到与其兴趣最为相似的其他簇内。仿真测试表明,算法稳定高效,搜索成功率和查找效率均优于传统的搜索算法。     

车联网数据流的多维服务质量改进异构计算最早完成时间调度算法

针对车联网中数据流分布式处理的调度问题,提出了多维服务质量(QoS)改进异构计算最早完成时间(HEFT)调度算法.首先,分别建立了车联网中数据流的分布式处理任务的带权有向无环图模型和车联网分布式计算资源的七维QoS属性带权无向拓扑结构图模型.其次,改进经典的HEFT调度算法中的列表构造方法为最高层最小后继任务优先列表构造方法; 同时,将车联网分布式计算资源的七维QoS属性进行分组、降维,转化为两维综合属性优先权:计算性能优先权和通信性能优先权,形成了两种不同用户偏好的多维QoS改进HEFT调度算法.最后,通过算例分析表明:两种不同用户偏好的多维QoS改进HEFT调度算法综合性能优于经典的HEFT调度算法和轮询调度算法.     

基于蚁群算法的非结构化P2P搜索机制的研究

通过对P2P中资源搜索技术的研究,针对非结构化P2P网络中的传统洪泛搜索机制中的路由盲目性和产生过多冗余消息等缺点,提出一种基于蚁群算法的非结构化P2P搜索机制.蚁群算法是一种新型的优化算法,利用蚁群算法信息素的正反馈机制指导查询请求消息的转发,将查询请求消息尽量发往资源可能存在的节点上.实验结果表明,该算法在查询成功率和查询消息的传送次数方面都优于洪泛搜索算法,提高了算法的有效性.     

基于P2P的教育资源网络设计

在网络中搜索各种教育资源时,通用的搜索引擎很难满足特定的需求。P2P网络是一种有效的资源共享和搜索方式。通过分析P2P网络的基本结构和资源共享特点,提出了一种基于P2P的教育资源网络（PBERN）模型。PBERN是由教育资源实体“自组织”组成的分布式、虚拟、动态和松散的纯P2P网络。     

CompuP2P: An Architecture for Internet Computing Using Peer-to-Peer Networks

Internet computing is emerging as an important new distributed computing paradigm in which resource intensive computing is integrated over Internet-scale networks. Over these large networks, different users and organizations share their computing resources, and computations take place in a distributed fashion. In such an environment, a framework is needed in which the resource providers are given incentives to share their resources. CompuP2P is a lightweight architecture for enabling Internet computing. It uses peer-to-peer networks for sharing of computing resources. CompuP2P create dynamic markets of network accessible computing resources, such as processing power, memory storage, disk space, etc., in a completely distributed, scalable, and fault-tolerant manner. This paper discusses the system architecture, functionality, and applications of the proposed CompuP2P architecture. We have implemented a Java-based prototype, and our results show that the system is light-weight and can provide almost a perfect speedup for applications that contain several independent compute-intensive tasks     

A flabellate overlay network for multi-attribute search

Peer-to-peer (P2P) technology provides a popular way of distributing resources, sharing, and locating in a large-scale distributed environment. However, most of the current existing P2P systems only support queries over a single resource attribute, such as file name. The current multiple resource attribute search methods often encounter high maintenance cost and lack of resilience to the highly dynamic environment of P2P networks. In this paper, we propose a Flabellate overlAy Network (FAN), a scalable and structured underlying P2P overlay supporting resource queries over multi-dimensional attributes. In FAN, the resources are mapped into a multi-dimensional Cartesian space based on the consistent hash values of the resource attributes. The mapping space is divided into non-overlapping and continuous subspaces based on the peer’s distance. This paper presents strategies for managing the extended adjacent subspaces, which is crucial to network maintenance and resource search in FAN. The algorithms of a basic resource search and range query over FAN are also presented in this paper. To alleviate the load of the hot nodes, a virtual replica network (VRN) consisting of the nodes with the same replicates is proposed for replicating popular resources adaptively. The queries can be forwarded from the heavily loaded nodes to the lightly loaded ones through VRN. Theoretical analysis and experimental results show that FAN has a higher routing efficiency and lower network maintenance cost over the existing multi-attribute search methods. Also, VRN efficiently balances the network load and reduces the querying delay in FAN while invoking a relatively low overhead.     

A dynamic framework for integrated management of all types of resources in P2P systems

Traditional Peer-to-Peer (P2P) systems were restricted to sharing of files on the Internet. Although some of the more recent P2P distributed systems have tried to support transparent sharing of other types of resources, like computer processing power, but none allow and support sharing of all types of resources available on the Internet. This is mainly because the resource management part of P2P systems are custom designed in support of specific features of only one type of resource, making simultaneous access to all types of resources impractical. Another shortcoming of existing P2P systems is that they follow a client/server model of resource sharing that makes them structurally constrained and dependent on dedicated servers (resource managers). Clients must get permission from a limited number of servers to share or access resources, and resource management mechanisms run on these servers. Because resource management by servers is not dynamically reconfigurable, such P2P systems are not scalable to the ever growing extent of Internet. We present an integrated framework for sharing of all types of resources in P2P systems by using a dynamic structure for managing four basic types of resources, namely process, file, memory, and I/O, in the same way they are routinely managed by operating systems. The proposed framework allows P2P systems to use dynamically reconfigurable resource management mechanisms where each machine in the P2P system can at the same time serve both as a server and as a client. The pattern of requests for shared resources at a given time identifies which machines are currently servers and which ones are currently clients. The client server pattern changes with changes in the pattern of requests for distributed resources. Scalable P2P systems with dynamically reconfigurable structures can thus be built using our proposed resource management mechanisms. This dynamic structure also allows for the interoperability of different P2P systems.     

Data resource discovery model based on hybrid architecture in data grid environment

Today, the management of massive data collections draws much attention as data grids have been developed to deal with large computational problems and provide the opportunity for sharing geographically distributed resources for large‒scale data‒intensive applications. Therefore, finding an effective approach to discover data resources in order to promote better interactions between application communities or virtual organizations becomes a critical challenge. Traditional grid resource discovery models are mostly based on central and hierarchical architecture that can lead to bottlenecking with the expansion of the grid scale. Although the Peer‒to‒Peer (P2P) technique is integrated into the grid in order to improve the performance in recent years, each P2P structure still has drawbacks that require several compensatory strategies. In this paper, based on the unstructured super‒node‒based architecture from the P2P system, we design a structured logic resource tree in each domain in order to effectively alleviate the load on the super‒node, and we propose a query recording learning algorithm based on this hybrid architecture to reduce traffic in the network and greatly shorten the response time. The model and algorithm are validated by simulations and compared with the traditional super‒peer model and the flooding‒based approach. Copyright © 2014 John Wiley & Sons, Ltd.     

基于语义覆盖网的P2P信息共享系统研究

现有P2P信息共享系统存在仅支持粗粒度、弱语义共享以及系统效率低等局限性,限制了其更大规模、更高层次的应用。基于资源相似节点通过信息聚类聚集在同一主题域,实现节点资源有序组织的思想,提出了一种基于语义覆盖网的P2P信息共享系统,建立由资源层、信息服务中心层、语义覆盖网络层和应用层四个层次组成的系统框架结构,并阐述了系统流程。分析表明,该系统有效优化了网络性能,可扩展性好,可以胜任不同的网络规模。     

Measuring web feature impacts in Peer-to-Peer file sharing systems

In Peer-to-Peer (P2P) file sharing systems, the presentation of resource attributes organized in different web features can influence users’ selection. However, this has been only qualitatively speculated without concrete analysis. In this paper, we conduct extensive quantitative measurements on the impacts of these attributes by crawling web pages of a BitTorrent site, “5QZone”. The measurement lasts for 31 days, and 168,610 records containing 11,228 distinct resources have been collected. We further compare it with one-day commercial measurement data from a hybrid file sharing site, “Xunlei”, which contains 5,473,283 resources for 5,156,696 participating users. The finding is twofold. On one hand, it confirms the above qualitative speculation; on the other hand, it shows more significant results: (1) with the highlight feature on popular items, the downloads of each resource yield to a long-tail distribution, deviated from Zipf Law; (2) publications with attracting titles disseminate substantially faster than others; (3) publisher authority feature has limited influence on depressing low quality resources; (4) other features such as presenting resource categories and sizes also affect user behavior. We further demonstrate the implications of the web feature impact for system design and potential attackers.     

A secure collaboration service for dynamic virtual organizations

Nowadays, various promising paradigms of distributed computing over the Internet, such as Grids, P2P and Clouds, have emerged for resource sharing and collaboration. To enable resources sharing and collaboration across different domains in an open computing environment, virtual organizations (VOs) often need to be established dynamically. However, the dynamic and autonomous characteristics of participating domains pose great challenges to the security of virtual organizations. In this paper, we propose a secure collaboration service, called PEACE-VO, for dynamic virtual organizations management. The federation approach based on role mapping has extensively been used to build virtual organizations over multiple domains. However, there is a serious issue of potential policy conflicts with this approach, which brings a security threat to the participating domains. To address this issue, we first depict concepts of implicit conflicts and explicit conflicts that may exist in virtual organization collaboration policies. Then, we propose a fully distributed algorithm to detect potential policy conflicts. With this algorithm participating domains do not have to disclose their full local privacy policies, and is able to withhold malicious internal attacks. Finally, we present the system architecture of PEACE-VO and design two protocols for VO management and authorization. PEACE-VO services and protocols have successfully been implemented in the CROWN test bed. Comprehensive experimental study demonstrates that our approach is scalable and efficient.     

Reputation-based dependable scheduling of workflow applications in Peer-to-Peer Grids

Grids facilitate creation of wide-area collaborative environment for sharing computing or storage resources and various applications. Inter-connecting distributed Grid sites through peer-to-peer routing and information dissemination structure (also known as Peer-to-Peer Grids) is essential to avoid the problems of scheduling efficiency bottleneck and single point of failure in the centralized or hierarchical scheduling approaches. On the other hand, uncertainty and unreliability are facts in distributed infrastructures such as Peer-to-Peer Grids, which are triggered by multiple factors including scale, dynamism, failures, and incomplete global knowledge.In this paper, a reputation-based Grid workflow scheduling technique is proposed to counter the effect of inherent unreliability and temporal characteristics of computing resources in large scale, decentralized Peer-to-Peer Grid environments. The proposed approach builds upon structured peer-to-peer indexing and networking techniques to create a scalable wide-area overlay of Grid sites for supporting dependable scheduling of applications. The scheduling algorithm considers reliability of a Grid resource as a statistical property, which is globally computed in the decentralized Grid overlay based on dynamic feedbacks or reputation scores assigned by individual service consumers mediated via Grid resource brokers. The proposed algorithm dynamically adapts to changing resource conditions and offers significant performance gains as compared to traditional approaches in the event of unsuccessful job execution or resource failure. The results evaluated through an extensive trace driven simulation show that our scheduling technique can reduce the makespan up to 50% and successfully isolate the failure-prone resources from the system.     

ERSChain: Towards secure and flexible educational resource sharing using consortium blockchain and revocable ciphertext-policy attribute-based encryption

Sharing high-quality educational resources has become an effective way to promote educational equity. The traditional educational resource sharing platforms using centralized storage architecture have security issues. Recently, many studies use blockchain to achieve secure sharing of educational resources. However, the existing blockchain-based educational resource sharing schemes only use blockchain as a storage tool, and have issues such as low sharing efficiency, without considering copyright security, and lack of a trusted sharing environment, which prevents the large-scale sharing of educational resources. In response, we propose ERSChain, a novel blockchain-based educational resources sharing solution. First, we put forward a hybrid storage method that keeps the hash value of resource in the blockchain and stores the encrypted resource in the off-chain, which can alleviate the storage and computing pressure brought by massive educational resources while ensuring the integrity of resources. Second, we construct an efficient revocable ciphertext-policy attribute-based encryption algorithm to implement flexible access control and an outsourced decryption algorithm to achieve greater efficiency. Obtaining access to educational resources is possible when user's attributes meet the access policy and the user's identity does not exist in the revocation list. Third, we put forward a credit mechanism to adjust the user's credibility and a credit-based consensus mechanism to maintain the trusted sharing environment. Finally, security analysis and plentiful of experiments demonstrate that our proposed ERSChain achieves security assurance, has better applicability than similar works, and enables large-scale sharing of educational resources.