Utilization-Based Admission Control for Scalable Real-Time Communication

We propose a utilization-based schedulability and admission control mechanism for distributed systems with workload aggregation to achieve scalability. We use the differentiated services (diffserv) architecture to describe and illustrate our approach. Scalability of admission control is achieved by determining off-line safe levels of server utilization. Scalability during the connection lifetimes is provided by the aggregation mechanisms (for example, class-based scheduling) provided by the diffserv architecture. Our evaluations show that our system's admission probabilities are very close to those of significantly more expensive approaches, which do not allow for workload aggregation. At the same time, admission control overhead during flow establishment is very low.     

Patience is a Virtue: The Effect of Slack on Competitiveness for Admission Control

We consider the on-line competitiveness for scheduling a single resource non-preemptively in order to maximize its utilization. Our work examines this model when parameterizing an instance by a new value which we term the patience. This parameter measures each job's willingness to endure a delay before starting, relative to this same job's processing time. Specifically, the slack of a job is defined as the gap between its release time and the last possible time at which it may be started while still meeting its deadline. We say that a problem instance has patience , if each job with length J has a slack of at least ·J.Without any restrictions placed on the job characteristics, previous lower bounds show that no algorithm, deterministic or randomized, can guarantee a constant bound on the competitiveness of a resulting schedule. Previous researchers have analyzed a problem instance by parameterizing based on the ratio between the longest job's processing time and the shortest job's processing time. Our main contribution is to provide a fine-grained analysis of the problem when simultaneously parameterized by patience and the range of job lengths. We are able to give tight or almost tight bounds on the deterministic competitiveness for all parameter combinations.If viewing the analysis of each parameter individually, our evidence suggests that parameterizing solely on patience provides a richer analysis than parameterizing solely on the ratio of the job lengths. For example, in the special case where all jobs have the same length, we generalize a previous bound of 2 for the deterministic competitiveness with arbitrary slacks, showing that the competitiveness for any 0 is exactly 1+1/(+1). Without any bound on the job lengths, a simple greedy algorithm is (2+(1/))-competitive for any <0. More generally we will find that for any fixed ratio of job lengths, the competitiveness of the problem tends towards 1 as the patience is increased. The converse is not true, as for any fixed <0 we find that the competitiveness is bounded away from 1, no matter what further restrictions are placed on the ratio of job lengths.     

可提供预约视频点播服务的一种加权入口控制算法

一个视频点播系统需要有大容量的存储空间和高速的输入／输出带宽,在视频点播的高峰时期,经常会出现系统资源供不应求的情况,这就需要有一种策略来决定如何管理用户请求,以及以什么样的顺序为用户提供服务,文中提出了一个新的入口控制算法：WMQL（Weighted Maximal Queue Length)调度,在选择要发送的视频段时,不仅考虑了视频的请求队列长度,还考虑了用户的请求等待时间。接着又提出了一个改进的调度方案：AWMQL（Advanced WMQL)调度,这种调度策略允许用户进行预约,而且尽量在用户的等待容忍度范围内满足用户请求,最后,进行了模拟试验,结果表明,AWMQL调度算法可以有效地增加系统的吞量,同时实现了较好的公平性。     

一种基于动态阈值的简化接纳控制策略

在线多媒体业务中,主机和网络瓶颈限制了系统能提供的最大服务量。如何保证用户的服务质量,对不同服务类的请求进行接纳控制,从而使系统获得最大的收益成为关注的焦点。该文分析比较了原有接纳控制机制,提出了一种新的简化的基于动态阈值的策略,能够在保持接纳灵活性的同时保证高级用户的优先性。理论分析和模拟仿真表明,该策略相对于以往几种接纳策略具有一定优势,且这种优势随着高级服务密度的增大及其收益率的提高而越发明显。     

基于在线测量的视频服务器接纳控制

实时多媒体系统中,有限的磁盘I/O带宽和缓存空间使得接纳控制显得更为重要。针对传统算法接纳控制方面的不足,论文提出基于在线测量的VBR视频服务器接纳控制算法。通过在线测量系统所剩资源和周期容限的幅度变化来实时调节调度周期的大小,不但简化了接纳过程,节约了系统资源,提高了算法的可实现性,而且也使得系统的所剩资源达到更优的“等量”平衡。结果表明,系统的综合性能指标明显提高。     

基于测量的接纳控制研究

与传统的接纳控制算法相比,基于测量的纳控制有诸多优点,首先它无需知识应用的流量模型,其次它能动态适应网络的负载变化,提高网络资源的利用率。文中分析了基于测量的接纳控制的基本思想,并在此基础上提出和实现了一种自适应的接纳控制算法（Adaptive Measurement-Based Admission Control,AMBAC).作者通过实验对该算法进行了验证,发现在系统资源利用率（或接纳能力）接近的情况下,与传统的（固定时间窗口的）,MBAC相比,AMBAC能达到更低的平均分组丢失率。     

Heterogeneous CPU Services Using Differentiated Admission Control

We present an adaptive rate-controlled scheduler for heterogeneous applications running on general purpose computers. Our scheduler can effectively support diverse application requirements. It employs uniform rate-based sharing. Application heterogeneity is satisfied by partitioning CPU capacity into service classes, each with a different criterion for admission control. As a result, we are able to provide at once guaranteed performance, flexible allocation of rates with excellent scalability and intermediate service classes offering tradeoffs between reserved rate utilization and the strength of guarantees. Our scheduler has been implemented in Solaris 2.5.1. It runs existing applications without modifications. We present experimental results showing the scalability, efficiency, guaranteed performance, and overload performance aspects of our scheduler. We demonstrate the importance of priority inheritance implemented in our scheduler for stable system performance.     

准入控制研究综述

准入控制是研究网络QoS问题的一个重要方面,目前出现的相关研究可以分为基于模型的准入控制和基于测量的准入控制二类。介绍了二种基于模型的准入控制机制,其核心路由器都不需要保存每流的状态。基于测量的准入控制首先列出MBAC所采用的测量机制和准入控制算法,之后对EMBAC的原理加以介绍。在分析各准入控制机制原理的基础上,总结和对比了二类准入控制机制的优缺点、所支持的业务类型,最后分析了实现各准入控制机制所需的进一步工作。     

一种基于测量的动态公平接纳控制算法

接纳控制算法是接纳控制的核心,在基于参数和基于测量的这两类接纳控制算法中,基于测量的接纳控制无需知道应用的流量模型,其次它能动态适应网络的负载变化,提高网络资源的利用率;然而最新的研究表明,仅仅追求高接纳率的接纳控制算法会造成对不同带宽QoS需求的连接的接纳非公平性,并且历经多跳的流更不易被接纳;文章的目的是解决基于测量的接纳控制算法的非公平性问题,文中分析了基于测量的接纳控制的基本思想和非公平性产生的原因,并在此基础上提出和实现了一种基于测量的HR接纳控制算法;仿真结果表明,该算法在以降低很小的接纳率的代价下,能有效地克服基于测量类接纳控制算法的非公平性问题。     

呼叫接纳的QoS算法研究

针对如何在系统资源利用率和用户服务质量(QoS)满意度之间达到一种平衡这一问题,按照码分多址接入(CDMA)系统要求,提出了基于用户中断概率的呼叫接纳控制(CAC)算法.呼叫接纳控制是无线通信网络无线资源管理中一个重要的组成部分,CAC策略依据一定的准则决定呼叫到达请求的允许接入或拒绝接入,其中策略设计的好坏直接影响着网络的性能和资源利用率.将平均中断概率定义为业务的QoS,对用户的呼叫进行接纳控制.实验结果表明,中断概率可以成为呼叫接纳的主导因素.     

云计算环境中SaaS的接入控制和调度策略研究

SaaS是一种基于网络的软件应用模式,是服务提供商将应用软件统一部署在自己的服务器上,用户根据自己的实际需要,通过互联网向服务提供商订购并支付自己所需的服务。在未来,SaaS模式是占主导地位的云服务模型。文中阐述SaaS的基本概念,介绍了SaaS的参考结构以及服务流程,分析概括了不同类型的服务要求的接人控制策略,总结了不同性能要求作业的调度策略,最后结合已有的云计算环境下的SaaS接入控制和调度策略研究成果,展望了未来的研究方向和亟待解决的关键问题。     

Admission Control Algorithm for Guaranteeing Real-Time Anycast Flow

［1］S. Deering,R. Hinden. Internet Protocol version 6(Ipv6)specification, RFC2460, Dec. 1998［2］R. Hinde, S. Derring. IP Version 6 Addressing Architecture,RFC 1884, Dec. 1995［3］S. Bhattacharjee, M. H. Ammar, E. W. Zegura, V. Shah,Z.Fei. Application-Laye     

基于CATV网络的视频服务器接入控制分析

接入控制是视频服务器软件的必要组成部分。该文定义了磁盘与网络接口卡数据丢失率和带宽利用率的计算方法,并以其为主要控制指标,比较了逐周期测试法、卷积法和正态分布法的接入控制计算结果。选择逐周期测试法作为接入控制计算方法,保证服务器提供预定服务质量,并有较高的资源利用率。该文同时给出了预读数据对资源利用率的影响。     

WCDMA系统级仿真技术与接入控制仿真研究

介绍了系统级仿真技术的特点和工作流程，分析了基于OPNET网络仿真软件的WCDMA系统建模方法，并以一种改进的接入控制算法为例，实现了在该WCDMA系统级仿真平台上的仿真。     

巧用Access实现一种条形码可自动生成的录取通知书打印报表

将一种条形码技术,结合Access数据库报表,实现一个条形码可自动生成,且具有自动套打功能的录取通知书打印报表,解决了在招生结束后短时间内完成录取通知书的制作工作,在新生报到时,工作人员只需使用扫瞄器读取通知书上的条形码信息就能迅速准确定位到学生,大幅提高了迎新的效率和准确性。     

Control-theoretic Analysis of Admission Control Mechanisms for Web Server Systems

Web sites are exposed to high rates of incoming requests. The servers may become overloaded during temporary traffic peaks when more requests arrive than the server is designed for. An admission control mechanism rejects some requests whenever the arriving traffic is too high and thereby maintains an acceptable load in the system. This paper presents how admission control mechanisms can be designed with a combination of queueing theory and control theory. In this paper we model an Apache web server as a GI/G/1-system and then design a PI-controller, commonly used in automatic control, for the server. The controller has been implemented as a module inside the Apache source code. Measurements from the laboratory setup show how robust the implemented controller is, and how it corresponds to the results from the theoretical analysis.     

Delay Control and Parallel Admission Algorithms for Real-Time Anycast Flow

An anycast flow is a flow that can be connected to any one of the members in a group of designated (replicated) servers (called anycast group). In this paper, we derive a set of formulas for calculating the end-to-end delay bound for the anycast flows and present novel admission control algorithms for anycast flows with real-time constraints. Given such an anycast group, our algorithms can effectively select the paths for anycast flows' admission and connection based on the least end-to-end delay bounds evaluated. We also present a parallel admission control algorithm that can effectively calculate the available paths with a short delay bound for different destinations in the anycast group so that a best path with the shortest delay bound can be chosen.     

遗传算法与神经网络在接纳控制中的应用

ATM网络的业务量控制是ATM网络中的关键技术之一。连接接纳控制是业务量控制的一种,对业务源进行控制。该文采用遗传算法和神经网络对ATM网络进行连接接纳控制,是一种比较可行的方法。     

网络准入控制技术的应用研究

文章针对目前广泛采用的网络准入技术进行了分析、比较,结合应用“端点准入防御(EAD)”系统的体会,提出了部署EAD网络准入控制系统的具体措施.     

无线网络时变带宽业务的准入控制性能分析

无线蜂窝网络的通话准入控制方法与通话的 Qo S以及无线信道的利用率密切相关 .使用 Markov过程得出了业务带宽需求时变状况下系统性能 (通话的切换掉线概率、并发掉线概率、阻塞概率以及信道利用率 )的理论模型 .通过数值结果分析了系统负载、用户的移动、通话的持续时间对系统性能的影响