共查询到19条相似文献,搜索用时 78 毫秒
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将宏观移动性管理的主机标识协议(HIP)应用于分布式移动性管理(DMM)构架,并将聚合服务器(RVS)与DMM中的移动性接入路由MAR功能集成于分布式接入网关(D-GW)。采用扩展HIP协议数据包头的参数,在注册D-GW的HIP BEX消息中携带切换前D-GW的主机标识符的二元组(HIT,IP地址),新D-GW根据此二元组信息向前一个D-GW注册并建立的隧道,将缓存在前D-GW中的数据转给新D-GW。这一切换机制可有效地保证数据完整性,仿真结果表明该方法能有效减少总的信令开销,同时基于HIP的移动性管理使节点的安全性得到了保证。 相似文献
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移动支持协议切换性能研究 总被引:2,自引:1,他引:1
切换是移动支持协议研究的重要内容,其性能好坏对移动网络的性能和服务质量提供具有至关重要的影响.在合适的网络模型和切换模型的基础上,通过理论分析和数值仿真的方法对各类移动支持协议(包括移动IP与微观移动协议以及不同的微观移动协议)的切换性能进行了深入的研究和比较.结果表明,切换性能受无线网络参数和移动支持协议的路径更新算法两个因素影响;采用微观移动协议时的切换性能好于只使用移动IP时的情形;在所有微观移动协议中,MIP-RR和MMP协议中的路径更新算法切换性能最佳. 相似文献
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移动主机(MH)在域间切换时延迟较长,不能实现快速切换。为支持MH域间的快速切换,该文在层次移动IP(HMIP)协议的基础上,提出了一种扩展的层次移动IP(eHMIP)协议,使得域间切换分组丢失延迟与MH到家乡网络之间的距离无关。以注册信令开销、切换分组丢失延迟为性能评价指标,对基于HMIP和eHMIP协议的切换性能进行分析。仿真实验结果表明:基于eHMIP协议的平均切换分组丢失延迟低于HMIP,但注册信令开销略高于HMIP。 相似文献
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改善移动节点通信质量的移动性管理最有效的方式是IP微移动.它的核心是切换管理.分析微IP协议和IP网络的不足之处.对全IP无线网络的移动性管理最关心的问题进行详细阐述,介绍一种目前主流的区域移动性管理协议PMIPv6.并分析其域内切换移动性管理机制。提出一种优化的基于网络的区域移动性管理域内切换管理方法.并与已形成IETF标准的切换管理方法进行性能分析比较.证明该方法可以有效地减少切换时延和位置更新信令代价. 相似文献
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一体化网络采用身份与位置分离映射机制,避免了传统网络中IP地址在语义上的双重属性问题,使得一体化网络不但可以有效解决核心网的路由可扩展问题,而且可以很好地支持节点的移动性.提出了一种一体化网络的移动性管理机制,详细描述了移动过程中该机制的协议流程,然后建立了一个移动过程信令开销分析模型,并给出了通过该模型计算最佳域大小的方法.根据建立的信令开销模型得出的各种信令开销,通过仿真得到了移动过程中不同参数对总信令开销的影响. 相似文献
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移动IP是支持IP移动性的协议,但是当其用于移动节点驻留在远离归属网络的外地网络时,将会产生严重的注册延迟,从而引起严重的包丢失和通信吞吐量的下降,为了改变这些不足,人们把移动节点的移动方式分为宏移动和微移动,并且提出了很多应用于微移动的移动性管理方案。文章深入研究了宏移动协议(RFC2002)和微移动协议的包丢失率,给出了计算公式,并且对计算结果进行了详细的分析。 相似文献
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现今Internet上的网络层协议IPv4的路由算法不支持主机漫游,为此IETF提出了一种新的基于现有IP协议的移动IP协议,现在移动IP协议是被提议的Internet标准。本文首先简要讲述了该协议的要求、目标和原理,然后对移动IP的应用进行了初步的探讨。 相似文献
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在研究移动自组网移动模型和无线路由协议的基础上,选取移动自组网中具有代表性的参考点群移动模型,基于ns2网络模拟平台,以参考点群组移动模型生成移动场景文件,应用层使用cbr数据流量,对OLSR无线路由协议在不同参数条件下的性能进行了模拟测试。通过对测试结果数据的详细分析,总结得出了OLSR无线路由协议在参考点群移动模型下端到端时延、报文交付率和路由负载三个方面的特点。为进一步研究移动自组网下基于OLSR协议的各种应用提供参考。 相似文献
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二次损失函数支持向量机性能的研究 总被引:7,自引:0,他引:7
通过比较二次损失函数支持向量机和标准支持向量机在模式识别问题上的表现,分析了二次损失函数支持向量机的性能.实验表明这两种支持向量机对平衡数据有相似的分类能力,但二次损失函数支持向量机的优化参数更小,支持向量更多;对不平衡数据,二次损失函数支持向量机的分类准确率随不平衡度的增加而急剧下降.研究同时表明基于RM界的梯度方法对某些数据无效.文中定性分析了导致上述各种现象的原因.最后提出了一种利用黄金分割原理缩减二次损失函数支持向量机支持向量的方法,该方法冗余的支持向量数不超过一个. 相似文献
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通信开销在云环境中无法忽略,但现有DAG(directed acyclic graph)工作流费用优化模型大都未考虑任务之间的通信开销,难以在实际云环境中应用.为此,提出带通信开销的工作流费用优化模型CA-DAG(communication aware-DAG),并在分层算法的基础上提出针对CA-DAG模型的调度算法CACO(communication aware cost optimization).CACO使用前向一致规则(forward consistent, FC)求解工作流的最小完工时间;根据逆向分层策略将任务分层,使费用优化问题从全局转化到局部;采用动态规划方法收集任务在选择服务时产生的零散“时间碎片”,增加任务的费用优化空间,改善费用优化效果.仿真实验结果表明,在考虑通信开销时,CACO费用优化效果较DTL(deadline top level),DBL(deadline bottom level),TCDBL(temporal consistency deadline bottom level)都有显著提高. 相似文献
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With the rapid growth of powerful mobile devices, to improve the speed and quality of customer service, mobilizing their workforce became more and more important to many companies. Consequently, all kinds of enterprise applications, policies and data access are enabled through mobile platforms. However, how to manage such various mobile types and mobile applications and to integrate them with existing enterprise IT infrastructure becomes a great challenge. In this paper, we propose a novel approach to manage the enterprise mobiles through IT service management by using standard ITIL processes. Motivated by real cases of insurance industry mobile solution, firstly, a system architecture named BlueStar is designed which integrated ITIL-compliant mobile management and enterprise IT service management into a uniform platform. Secondly, typical ITIL processes and best practices: Change and configuration workflow are introduced for mobility management. Thirdly, the BlueStar system included device management component is implemented and evaluated by the motivating cases. 相似文献
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PMIPv6协议是MIPv6协议的扩展,是一种基于网络的移动性管理技术。在PMIPv6协议中,由网络负责探测节点的移动路径并初始化所必须的移动信令,MN不参与切换过程,能量消耗低,但是PMIPv6依赖于一个独一无二的处于网络中央的本地移动锚点( LMA),容易导致瓶颈问题,且带来切换时延长、通信路径非最优等问题。基于此,提出了一种基于PMIPv6的移动性管理方案,使用簇对移动接入网关(MAG)进行分组。在每个簇中选举出一个头移动接入网关(HMAG)作为簇头,由HMAG代替LMA负责执行本簇内的移动切换以及最优化数据通信路径,这样就减少了LMA的负载,延长了网络寿命。分析及仿真结果表明所提方案与PMIPv6相比在总开销、LMA负载等方面都有较大的改善。 相似文献
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This paper describes the modelling of a two multicast group key management protocols in a firstorder inductive model, and the discovery of previously unknown attacks on them by the automated inductive counterexample finder Coral. These kinds of protocols had not been analysed in a scenario with an active intruder before. Coral proved to be a suitable tool for a job because, unlike most automated tools for discovering attacks, it deals directly with an open-ended model where the number of agents and the roles they play are unbounded. Additionally, Coral's model allows us to reason explicitly about lists of terms in a message, which proved to be essential for modelling the second protocol. In the course of the case studies, we also discuss other issues surrounding multicast protocol analysis, including identifying the goals of the protocol with respect to the intended trust model, modelling of the control conditions, which are considerably more complex than for standard two and three party protocols, and effective searching of the state space generated by the model, which has a much larger branching rate than for standard protocols. 相似文献
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成本控制是企业长久发展的命脉所在,一个工程项目从立项到完成需经过多个阶段,比如立项审批阶段、立项可研阶段、初步设计阶段、设计阶段、招投标阶段、施工阶段和竣工结算阶段等。每一个阶段都有它独特的计价方式和成本控制方法。因此,每一个环节都对成本有不同程度的影响。通过阐述工程项目各个阶段的管理和控制内容,提出了有效降低工程成本和合理控制投资规模的措施,以供相关单位参考。 相似文献
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More resources are spent on maintaining software than for its development. Maintenance costs for large scale software systems can amount to somewhere between 40 and 67% of the total system life cycle cost. It is therefore important to manage maintenance costs, and to balance costs with benefits. Frequently this task is approached, at least in the literature, merely as a software cost estimation problem. Unfortunately, the creation of effort estimation models for maintenance – a primary requisite for cost calculation – has not yet been satisfactorily addressed. At the same time, project managers do not estimate costs first, but instead prioritize maintenance projects, trying to determine which projects to carry out (first) within their fixed budgets and resource capabilities. This essentially means that cost estimation is done qualitatively first before formal cost estimation techniques are employed. Recognizing the problems associated with standard, regression based estimation models, and focusing on the needs of software project managers, this research studied the process of project prioritization as an expert problem solving and decision making task, through concurrently taken (think aloud) protocols. Analysis of these protocols revealed that experts rarely make use of formal mathematical models to determine project priorities or resource needs, such as COCOMO or FPA, although project size is a key determinant of a project's priority. Instead, estimators qualitatively consider cost or value, urgency, and difficulty of a maintenance task, then prioritize projects accordingly, followed by a decision concerning further treatment of the problem. The process employs case based reasoning and the use of heuristics. While different experts may use different strategies, there exists great overlap in their overall prioritization procedure. 相似文献