虚拟计算环境中的DHT拓扑构建技术研究综述

基于互联网的虚拟计算环境(iVCE)是一种新型网络计算平台.互联网资源的成长性、自治性和多样性等自然特性给iVCE中的资源共享带来巨大的挑战.DHT覆盖网(简称DHT)具有可扩展、延迟低、可靠性高等优点,是iVCE实现资源有效共享的重要途径之一.拓扑构建是DHT的基础性关键技术,实现了DHT的动态维护与消息路由等基本功能.本文首先概述传统DHT的拓扑构建技术,主要包括各种典型DHT的动态维护机制与消息路由算法、支持复杂查询的DHT索引构建技术,以及支持管理域匹配的DHT分组构建技术等;进而针对互联网资源的特点,综述在iVCE中DHT拓扑构建技术的最新研究进展.本文在最后对DHT拓扑构建技术的未来发展方向进行探讨.     

无结构P2P网络搜索方法及其改进

对等(P2P)计算是未来网络中的关键技术,对等网络是实现下一代互联网的重要组成部分。如何高效地搜索P2P网络上的资源是P2P网络实现的最为关键的问题。在讲述对等网络的基本搜索方法的基础上,分析了许多改进的搜索方法,包括基于转发的改进方法、基于缓存的改进方法和基于覆盖网拓扑优化的改进方法。     

基于框架技术的通用虚拟计算平台的实现

通过分析目前几种虚拟计算环境的现状、特点及适用范围,针对聚合异构分散计算资源的需求,提出了一种基于框架技术的虚拟计算环境的实现方法.研究了虚拟计算环境的关键实现技术,主要包括计算平台的总体框架和服务组件,以及各个组成部分之间的关系和通信方式;并基于服务分层设计方法来优化计算服务的架构,对各服务组件进行了详细的设计,实现了虚拟计算平台系统.以地震资料数据处理为例进行了实验测试,测试结果表明,该虚拟计算框架具有一定的可行性和有效性,能够整合零散、异构的计算资源,尤其适用于性能差异明显的计算组织,为用户提供了透明的资源访问模式,提高了计算资源的利用率.     

移动自组网中感知拓扑失配的P2P覆盖网构建

对等计算主要关注构造在应用层的虚拟覆盖网络. 在上层的覆盖网络和底层的物理网络之间, 通常都存在着拓扑失配. 这种失配会导致P2P应用耗费相当大的通信开销. 在移动自组网中, 由于资源(比如带宽, 电池能量等)和节点移动性的限制, 拓扑失配问题变得更加严重. 而已有工作对这一问题没有进行充分的研究. 本文研究了移动自组网中的拓扑失配问题对非结构化P2P覆盖网中目标搜索的影响, 并提出一个分布式的、能感知拓扑失配的覆盖网络构建算法D-TAOC.分析和实验表明在D-TAOC构建的拓扑失配感知的覆盖网中, P2P应用能够在较少牺牲目标搜索效率的前提下, 明显地降低网络中的通信负载.     

ConEntity:一种基于进程的自主并发实体编程模型及其实现

本文在虚拟计算环境之上,研究支持具有自主能力、高并发的新型互联网应用开发方法,在已有的基于进程、面向并发的编程模型中引入实体建模机制,扩展出一种兼具进程和自主并发实体的程序设计模型ConEntity,并给出了形式化定义和描述.ConEntity模型具有表达性、并发性和可伸缩性的特点,能对虚拟计算环境资源高效、透明访问.通过扩展Erlang/OTP将其实现为Erlang语言设施UniAgent.本文的模型为在虚拟计算环境上快速直接构建具有自主、高并发能力实体的新型互联网应用提供了模型和语言上的支持.     

一种基于聚类的虚拟计算环境资源聚合方法

作为面向互联网资源共享的虚拟计算环境的实例,iVCE(Internet based virtual computing environment) for Memory致力于解决广域分布的内存资源的共享与综合利用问题.由于内存资源的特殊性,传统的资源管理方法很难适用.以iVCE for Memory作为背景,提出一种基于聚类的虚拟计算环境资源聚合方法,有效降低了资源聚合的问题规模;借鉴物理学中的力场和势能理论,建立了实现资源聚合的基本模型和力场-势能模型以及相应的分布式算法;通过基于真实网络拓扑的模拟,对两种模型和算法分别进行了评估和验证.     

基于框架的虚拟计算环境关键技术研究

通过分析目前几种虚拟计算环境的现状、特点及适用范围,针对中小规模、异构零散的的计算需求,提出一种基于框架技术的虚拟计算环境的实现方法,并结合框架技术设计了分层服务模型.基于复杂多样的、性能差距明显的计算资源的调度问题,提出了一种基于对等模式的随机自适应调度算法.该算法提供对关联任务的调度,适合异构的、资源规模较大的环境,尤其是计算资源差异明显的异构计算环境.实现了基于框架技术的虚拟计算原型系统,并通过实验测试对比算法的调度性能,最后将计算环境应用于实际的地震资料处理中.     

基于节点连通性排序的虚拟网络映射算法

对当今云环境下的数据中心来说,以虚拟资源租赁的运营方式具有极大的灵活性,尤其是以虚拟网络为粒度的资源租赁能够为用户提供更好的个性化需求支持。虚拟网络映射问题是指依据用户资源需求,合理分配底层主机和网络资源。现有的虚拟网络映射算法大多是针对随机拓扑设计的通用算法,未针对数据中心拓扑结构进行优化,映射效率有很大提升空间。针对数据中心的结构特点,提出了一种基于节点连通性排序的虚拟网络映射算法BS-VNE算法。首先,设计了一种最大生成算法来对虚拟节点重要程度进行求解和排序。该算法不仅基于虚拟节点的带宽和连通度,还基于虚拟节点在整个虚拟网络中的连通性来进行节点连通性的计算,以获得更加合理的排序结果。然后,根据虚拟节点连通性排序结果利用离散粒子群优化算法求解虚拟网络的映射解。在求解过程中,引入了针对数据中心结构的物理网络拓扑启发式规则,并将其组合到粒子搜索过程中,以提高映射算法的收敛速度。仿真实验结果表明,与现有算法相比,本文提出的算法可以提高物理网络的收益/成本比和资源利用率。     

基于区块链的虚拟电厂模型研究

新能源技术和互联网技术推动了电力系统由智能电网向能源互联网进化,未来能源互联网将以分布式能源作为主要的一次能源。虚拟电厂技术能够聚合分布式能源并建立虚拟电力资源交易,逐步成为分布式能源高渗透情况下的核心并网技术。针对以实时电价为驱动的未来能源互联网,结合区块链这一安全、透明、去中心化的分布式计算范式,建立基于区块链的虚拟电厂模型,通过区块链的激励机制将虚拟电厂协调控制手段和分布式能源独立并网行为有机联动,从而实现高效的分布式调度计算。仿真实验表明,所提模型满足能源互联网中分布式能源高渗透率、高自由度、高交易频率、高响应速度的并网需求。     

多关键字云资源搜索算法

云计算的核心是在虚拟化技术的基础上,通过互联网技术为用户提供动态易扩展的计算资源。利用中心服务器的计算模式来管控网络上大量云资源使得中心服务器成为整个系统的瓶颈,不利于云计算的大规模应用,因此提出使用对等网络技术构建分布式的云资源索引存储和查询系统,但是结构化拓扑系统维护比较复杂,一般不支持复杂搜索条件查询。本文提出了一种多关键字云资源搜索算法。在基于分层超级节点的云资源搜索算法基础上进行路由算法改进,希望实现多关键字的精确查询。对多关键字的生成、分割及存储做出了详细说明,提出一种有效的基于数据集的索引搜索策略,实现了包含三个或三个以上的关键字高效、准确查询。分析实验结果证明了算法明显提高了资源搜索的命中率,尤其是随着关键字数目的增多,不仅保证了资源搜索的命中率,同时大大增加了资源的召回率。     

虚拟计算环境中的可扩展分布式资源信息服务

基于网络资源的"成长性"、"自治性"和"多样性",近年来,人们提出以通用DHT(distributed Hash table)信息服务的形式实现网络资源信息的发布和查询.然而,现有的资源信息服务在通用性、易用性和自适应性等方面仍存在不足.针对虚拟计算环境iVCE(Internet-based virtual computing environment)的资源聚合需求,提出构建可扩展的分布式资源信息服务SDIRIS(scalable distributed resource information service).首先,提出采用自适应DHT(adaptive FissionE,简称A-FissionE)底层架构,以对上层应用透明的方式适应不同的系统规模和稳定性;其次,基于自适应DHT提出高效的多属性区间搜索算法(multiple-attribute range FissionE,简称MR-FissionE).理论分析和模拟结果表明,SDIRIS能够高效地实现资源信息的发布与查询功能.     

Internet-based virtual computing environment(iVCE):Concepts and architecture

Resources over Internet have such intrinsic characteristics as growth, autonomy and diversity, which have brought many challenges to the efficient sharing and comprehensive utilization of these resources. This paper presents a novel approach for the construction of the Internet-based Virtual Computing Environment (iVCE), whose sig- nificant mechanisms are on-demand aggregation and autonomic collaboration. The iVCE is built on the open infrastructure of the Internet and provides harmonious, transparent and integrated services for end-users and applications. The concept of iVCE is presented and its architectural framework is described by introducing three core concepts, i.e., autonomic element, virtual commonwealth and virtual executor. Then the connotations, functions and related key technologies of each components of the architecture are deeply analyzed with a case study, iVCE for Memory.     

Embedded DHT overlays in virtual computing environments

With the rapid development of computing and networking technologies, people propose to build harmonious, trusted and transparent Internet-based virtual computing environments (iVCE). The overlay-based organization of dynamic Internet resources is an important approach for iVCE to realizing efficient resource sharing. DHT-based overlays are scalable, low-latency and highly available; however, the current DHT overlay (SKY) in iVCE cannot satisfy the trust requirements of Internet applications. To address this...     

A Programming Language Approach to Internet-Based Virtual Computing Environment

There is an increasing need to build scalable distributed systems over the Internet infrastructure. However, the development of distributed scalable applications suffers from lack of a wide accepted virtual computing environment. Users have to take great efforts on the management and sharing of the involved resources over Internet, whose characteristics are intrinsic growth, autonomy and diversity. To deal with this challenge, Internet-based Virtual Computing Environment (iVCE) is proposed and developed to serve as a platform for distributed scalable applications over the open infrastructure, whose kernel mechanisms are on-demand aggregation and autonomic collaboration of resources. In this paper, we present a programming language for iVCE named Owlet. Owlet conforms with the conceptual model of iVCE, and exposes the iVCE to application developers. As an interaction language based on peer-to-peer content-based publish/subscribe scheme, Owlet abstracts the Internet as an environment for the roles to interact, and uses roles to build a relatively stable view of resources for the on-demand resource aggregation. It provides language constructs to use 1) distributed event driven rules to describe interaction protocols among different roles, 2) conversations to correlate events and rules into a common context, and 3) resource pooling to do fault tolerance and load balancing among networked nodes. We have implemented an Owlet compiler and its runtime environment according to the architecture of iVCE, and built several Owlet applications, including a peer-to-peer file sharing application. Experimental results show that, with iVCE, the separation of resource aggregation logic and business logic significantly eases the process of building scalable distributed applications.     

Building Efficient Overlays

Peer-to-peer (P2P) and Grid computing systems have emerged as popular models aiming at further utilizing Internet information and resources, complementing the available client–server services. However, the mechanism of peers randomly choosing logical neighbors without any knowledge about underlying physical topology can cause a serious topology mismatch problems between the overlay network and the physical underlying network. The topology mismatch problem brings a great stress in the Internet infrastructure and greatly limits the performance gain from various search or routing techniques in P2P and Grid systems. Aiming at alleviating the mismatch problem and reducing the unnecessary traffic, we have proposed two approaches, adaptive overlay topology optimization (AOTO) and location-aware topology matching (LTM) techniques, to reduce the total traffic cost and average query response time. Both AOTO and LTM are scalable and completely distributed in the sense that they do not require any global knowledge of the whole overlay network when each node is optimizing the organization of its logical neighbors. This paper shows the effectiveness of AOTO and LTM and compares the performance of these two approaches through simulation studies.     

基于非结构化P2P技术的资源信息服务

因特网资源的“分布性”、“自治性”和“多样性”等自然特性给资源的有效共享和综合利用带来了巨大的挑战。本文基于非结构化P2P技术提出了一种虚拟计算环境（iVCE）中的可扩展资源信息服务（SRIS）,并对SRIS的应用实例进行了模拟分析。     

Location awareness in unstructured peer-to-peer systems

Peer-to-peer (P2P) computing has emerged as a popular model aiming at further utilizing Internet information and resources. However, the mechanism of peers randomly choosing logical neighbors without any knowledge about underlying physical topology can cause a serious topology mismatch between the P2P overlay network and the physical underlying network. The topology mismatch problem brings great stress in the Internet infrastructure. It greatly limits the performance gain from various search or routing techniques. Meanwhile, due to the inefficient overlay topology, the flooding-based search mechanisms cause a large volume of unnecessary traffic. Aiming at alleviating the mismatching problem and reducing the unnecessary traffic, we propose a location-aware topology matching (LTM) technique. LTM builds an efficient overlay by disconnecting slow connections and choosing physically closer nodes as logical neighbors while still retaining the search scope and reducing response time for queries. LTM is scalable and completely distributed in the sense that it does not require any global knowledge of the whole overlay network. The effectiveness of LTM is demonstrated through simulation studies.     

Building a Scalable Bipartite P2P Overlay Network

The peer-to-peer (P2P) model, being widely adopted in today's Internet computing, suffers from the problem of topology mismatch between the overlay networks and the underlying physical network. Traditional topology optimization techniques identify physically closer nodes to connect as overlay neighbors, but could significantly shrink the search scope. Efforts have been made to address the mismatch problem without sacrificing the search scope, but they either need time synchronization among peers or have a low convergent speed. In this paper, we propose a scalable bipartite overlay (SBO) scheme to optimize the overlay topology by identifying and replacing the mismatched connections. In SBO, we employ an efficient strategy for distributing optimization tasks in peers with different colors. We conducted comprehensive simulations to evaluate this design. The results show that SBO achieves approximately 85 percent of reduction on traffic cost and about 60 percent of reduction on query response time. Our comparisons with previous approaches to address the topology mismatch problem have shown that SBO can achieve a fast convergent speed, without the need of time synchronization among peers.     

On investigating overlay service topologies

Recently, a moderate amount of work has been reported on the use of overlay networks to support value-added network services, such as multicasting, Quality-of-Service (QoS), security, etc. To design an overlay network, the first step is to choose an overlay topology connecting all the overlay service nodes. When considering overlay topologies, several questions need to be answered first: How overlay topologies affect overlay routing performance? Which topologies can provide satisfactory performance? How can we construct efficient overlay topologies connecting all the overlay nodes?In this paper, we focus on the overlay network topology construction issue. First, we evaluate and compare the performance and overhead of the existing overlay topologies. Second, we formalize the overlay topology construction problem and propose two new heuristic methods to construct efficient overlay topologies. Simulation results have demonstrated the efficiency of the two proposed approaches. It is shown that overlay service performance varies significantly with respect to different overlay topologies. Thus, it is important to choose an appropriate overlay network topology. The knowledge of IP-layer topology information also benefits significantly in constructing efficient overlay topologies as inferred from the results.