基于分形漏桶整形器的通用处理器共享系统性能分析

为了分析自相似业务流对通用处理器共享（GPS）系统性能的影响,研究了GPS系统性能与业务流自相似参数等因素之间的关系.通过使用分形漏桶的包络曲线对进入GPS系统的自相似业务流进行整形,推导了利用自相似业务流作为输入的GPS系统的队列长度和时延统计上界.数值结果与分析显示,基于分形漏桶的GPS系统性能模型对自相似业务流具有较好的性能.     

基于令牌漏桶法的数据记录技术

针对实时系统记录数据会引起系统运行速度缓慢、瘫痪、甚至＂死机＂的问题,提出了具有特色的令牌漏桶法。该方法通过创建循环队列数据池并根据数据池的数据量适时发放令牌和拥有令牌的任务自动选择CPU空闲时执行等技术实现。通过试验验证,在保证整个系统实时性、可靠性的前提下,该方法实现了实时记录数据的功能。     

Performance of adaptive token allocation in the leaky bucket

The leaky bucket is a popular method that can regulate traffic into an ATM broadband network. This paper examines a simple but innovative modification that would also provide priority to access the network. This is done by requiring cells of different classes to obtain different numbers of tokens before receiving their services. As a step further, a dynamic scheme can be used in which the tokens allocated to each class are changed according to the traffic load. Performance evaluations of mean cell delays and cell loss probabilities are obtained to provide insight into the behaviour of the system and to provide guideline for furture design.     

ATM突发性业务阻塞控制

在ＡＴＭ网里业务阻塞控制是一个十分重要的问题，本文对一种缓冲漏桶业务阻塞控制算法在突发性业务输入情况下的性能进行了计算机模拟分析，模拟结构表明缓冲漏桶算法是一种适合于突发性业务的阻塞控制算法，文章在模拟结果的基础上给出了缓冲漏桶算法中参量选择的算法。     

Estimating cell loss rates in high-speed networks with leaky bucket controlled sources

This paper deals with high-speed networks, such as the ATM network, over which data is transferred in cells or packets. Results based on asymptotic analysis of stochastic fluid flow models imply that these networks would have to be run at very low utilization to satisfy the stringent performance requirement of very low cell loss rates. Recent papers have quantified that asymptotic approximations can be quite bad with even a modest number of users sending traffic into the network. In this paper it is shown that two more assumptions in the asymptotic analysis may lead to significant overestimation of the cell loss rates. The more significant of these is the use of the underlying exponential ON durations if sources are policed. The second and less significant is the assumption of an infinite buffer. A new approximate nalytic method is then developed for estimating the cell loss rate with sources policed by a leaky bucket type mechanism. This method focuses directly on the problem of measuring cell losses in the presence of many sources simultaneously bursting in a time period small enough to cause buffer overflow. It turns out to be highly accurate even with some rather drastic simplifying assumptions.     

Bursty ATM user traffic allowed by a jitter tolerant leaky bucket and its impact on link utilization

In a network based on the asynchronous transfer mode (ATM), quality of service requirements have to be met even in the presence of users who send traffic as bursty as the policing device allows. For peak cell rate policing with a jitter tolerant leaky bucket, a periodic maximally bursty traffic pattern allowed by the leaky bucket is derived. The impact of this kind of bursty user traffic on the cell loss performance of the remaining sources is investigated by introducing, solving and applying the queueing model Geo(n) + P/D/1/K, where P stands for ‘periodic’. Taking bursty user traffic into account, it is shown that the maximal jitter or cell delay variation allocated to the user and tolerated by the leaky bucket is an important parameter for link utilization. The results help to answer the question under which conditions a shaping function is needed in conjunction with the usage parameter control function.     

ANALYSIS OF THE LEAKY BUCKET ALGORITHM FOR PRIORITY SERVICES

The leaky bucket algorithm with loss priorities is studied in this paper. The analytical expression of the relation among leaky bucket performance, statistical parameters of input traffic and leaky bucket, parameters for various priority services is obtained, and the effect of adjustment factor on leaky bucket performance of higher-priority service and lower-priority service is studied with two priority classes.     

Lowpass traffic policing mechanism based on the leaky bucket

A traffic throttle can be modelled as a gate with one input and two outputs: pass for accepted calls, and gap for rejected calls. The gate decides whether to pass or to gap an incoming call according to its policing mechanism. The authors show that a small modification to a leaky bucket policing mechanism yields a lowpass filter. The proposed mechanism is a new type of a nonlinear filter     

Efficient Transmission of MPEG-2 Coded Video Traffic over ATM Networks

Video traffic is expected to account for a significant share of the traffic volume in the future asynchronous transfer mode (ATM) networks. MPEG-2 proposed by Moving Picture Expert Group is one of the most promising compression techniques for such applications. One of the critical issues in MPEG-2 is to realize effective variable bit rate (VBR) video transfer thorough ATM networks. The Leaky Bucket (LB) scheme has been widely accepted as the usage parameter control (UPC) mechanism to police the VBR sources. We proposed a new Adaptive Dynamic Leaky Bucket (ADLB) congestion control mechanism, which is based on the LB scheme. Unlike the conventional LB, the leak rate of the ADLB is controlled using delayed feedback information of available bandwidth sent by the network. This scheme allows sources to get varying amounts of bandwidth over time, while reserving a minimum guaranteed bandwidth (MCR) for the entire duration of the connection. At the time of congestion, the leak rate of the ADLB is adjusted according to the feedback indicating the currently available bandwidth to the connection. The simulation results show that the end-to-end cell transfer delay and cell loss of each source has been improved significantly.     

基于漏桶的内容适配系统接纳控制

综合终端特征、内容对象语义特征和通信特征,根据系统负载情况估计用户感受到的服务质量,作为接纳控制的依据,并引入漏桶模型和PID控制法进行反馈控制,从而解决了在网页内容适配系统对内容进行动态适配时,由于异构用户服务请求的系统资源需求特征差异很大,导致适配资源耗费过大,难以有效进行的问题。理论说明和仿真测试结果表明该方法从一定程度上提高了用户的主观服务质量,为内容适配的接纳控制研究做出了有益的探索。     

PERFORMANCE ANALYSIS OF LEAKY BUCKET ALGORITHM WITH BURSTY TRAFFIC INPUT IN ATM NETWORKS

A bursty traffic model is introduced in this paper to describe the statistical characteristics of packet video. The performance of leady bucket algorithm with bursty traffic input is analyzed. The influences of various parameters on QOS (Quality of Service) are investigated. The analysis shows that although the loss probability decreases through expanding the buffer capacity, the delay and delay jitter increase, whose effect on QOS will not be negligible.     

ATM业务监控的最差通过流分析及二级漏桶算法

讨论了一定算法下最差通过流的概念，强调了最差通过流的参数特性是评价一种业务监控算法的重要指标之一。对基本漏桶和缓冲漏桶逄法进行了比较。     

Buffered and Unbuffered Leaky Bucket Policing: Guaranteeing QoS,Design and Admission Control

Traffic shaping and smoothing using buffers or leaky buckets does not necessarily improve Quality of Service (QoS). In fact there is a trade-off between controlling user traffic and guaranteeing QoS to the users. We consider the first two stages (source node and border node before entering a network cloud) of an end-to-end QoS problem and assume that the QoS requirements across each of the two stages are given. We formulate and solve a mathematical programming problem to select optimal leaky bucket parameters that would enable high-speed telecommunication network providers to optimize traffic policing subject to guaranteeing a negotiated Quality of Service requirement across the first stage namely the source end. We address both the buffered and unbuffered leaky bucket cases where using fluid models we characterize the output process from the leaky buckets for general traffic sources. Using the optimal leaky bucket parameters and output characteristics (effective bandwidths in particular), we solve design and connection admission control problems given QoS requirements at the second stage, namely the border node.     

业务优先级感知的网络流量调度机制

针对网络中业务数据流过大、分布不均匀所造成的网络拥塞,提出一种优先级感知的动态网络流量调度机制.利用令牌桶算法,根据业务优先级的不同为不同业务分配不同速率的令牌,以实现业务优先级的划分;综合考虑业务的优先级及用户节点剩余缓存空间,对不同的业务采取不同的处理方式;同时,以流量到达因素、服务因素及节点缓存为指标定义了一种网络流量调度机制性能指标——分组丢失率.数值结果表明,所提机制可以对网络中业务优先级进行合理的划分,从而有效利用网络资源,预防网络拥塞,提升网络性能,为用户提供更加稳定可靠的网络服务.     

基于FDTD的微带漏波天线分析的新方法

使用时域有限差分法对微带漏波天线进行数值仿真,得到了微带漏波天线TE01模下的电场分布,对微带漏波天线的电波传播特性进行初步的讨论.提出新的经验计算公式微带漏波天线漏波传播系数,所得漏波传播系数曲线与实测数据以及比较数据十分吻合.     

基于不同等效面的漏波天线辐射特性研究

基于等效原理计算了一款分别使用线电流源与线磁流源激励的一维无限长漏波天线的总场辐射方向图和漏波辐射方向图.应用等效原理,两种辐射方向图均分别使用了等效面电流和等效面磁流两种不同的等效方法推导.使用谱域法推导出天线总场与漏波辐射场方向图的解析解并使用互易性原理推导出总场的辐射方向图以作对比.对比结果显示不同等效面得出的漏波场辐射方向图不同.     

基于FDTD的微带缝隙漏波天线分析

应用时域有限差分法(FDTD)对微带缝隙漏波天线进行分析,直观地得到了微带缝隙漏波天线内部的电场分布。提出了一条有效的经验公式,成功地计算了微带缝隙漏波天线的漏波传播系数,与实验数据吻合较好。比较了不同缝隙宽度和微带宽度对微带缝隙漏波天线性能的影响。证明了在微带漏波天线上开缝可以有效地减少天线尺寸及降低天线的工作频率。     

具有漏桶控制的ATM复接器性能分析

提出了用间断贝努利过程可近似描述突发源经漏桶后的输出过程。分析了综合业务环境下，具有漏桶控制的ＡＴＭ复接器的性能。计算机模拟验证了分析的正确性。     

模糊漏桶在ATM网络UPC中的应用

本文提出了模糊漏桶模型，研究了它与普通漏桶在用户量参数控制（ＵＰＣ）中的作用。由于ＣＡＣ初步协议的不完全合理性，在实际应用中动态调节是必要的；仿真结果表明在降低信元丢失率、时延和时延抖动方面，及在动态利用网络资源方面，模糊漏桶算法要比普通的优越。我们还给出了合适的模糊控制规则。