基于业务流偏好的多QoS目标决策分层路由研究

以移动自组织网络分层路由中网关与网关间多路径优选问题为研究背景,研究了满足业务流特定QoS需求的保障方法,体现了"按需服务"的思想.给出了业务流QoS需求偏好的表示、转化及其计算的策略和方法,并扩展了GPSR路由算法,提出了基于业务流偏好的多QoS目标决策分层路由TMQODR算法,使其具有QoS选路功能,能根据业务流的QoS偏好选择最合适的路径.通过相关性能分析及仿真实验验证了算法的有效性.     

QoS驱动的服务动态替换方法

在基于SOA(Service-Oriented Architecture)的软件中,为了适应用户对软件QoS(Quality of Service)值要求的改变或是组成软件的Web服务本身QoS值的不稳定,需要对软件进行重配置,使其QoS值达到用户要求。提出一个QoS驱动的动态替换算法,通过对软件的QoS的监测结果或用户所提出的QoS需求,确定动态替换目标。通过目标的替换,使配置后的软件满足用户需求。理论分析和实验结果都说明了算法的可行性和有效性。     

自相似网络业务流建模方法与比较

随着网络服务的发展．多媒体数据逐渐成为网络业务流的主要内容。基于多媒体数据的网络业务流对服务质量(QoS)提出了更高的要求。通常对服务质量的要求必然转化为对网络资源的需求，然而这个需求的量化必须基于一个能够准确描述网络变化的网络业务流数学模型。同时，网络业务流的不同特征以及研究目的的不同使得自相似网络业务流建模成为一个挑战性的问题。近来，一系列的方法被用于自相似网络业务流建模，本文的作者将这些方法分为两类共四种方法。本文全面分析比较了这些方法，并提出一种分类机制用于根据不同的研究需要确定相应的建模方法。     

一种支持混合QoS属性的服务选择方法

当前的服务选择方法大都假设所有服务的QoS(Quality of Service)属性值必须均为确定的实数,并未考虑QoS属性的模糊性。这个假设在实际应用需求中具有一定的局限性,还会丢失大量的数据信息。为增强QoS表达能力,将QoS属性值描述成精确数值型、区间数值型、模糊数值型。同时,用序关系向量表示用户对不同QoS属性的需求偏好,将其转换成用户对QoS属性的主观权重,并采用熵权法计算QoS属性的客观权重。在此基础上,采用相对优势度算法给出混合QoS属性的服务选择过程。最后通过模拟和实验验证,证明相对优势度算法的有效性与合理性。     

聚集业务流特性与QoS性能界限的研究

文章首先对业务流特性模型进行了概述，然后以母函数为工具阐述了经典的有效带宽理论并获得了聚集业务流的QoS(Quality-of-Service)性能界限，最后以网络演算为工具对受限敌对流方法进行了扩展，获得了更一般的聚集业务流特性与QoS性能界限。本文的研究结果适用于区分服务DiffServ(DiHerentiated Services)的边界节点。     

基于语义的QoS感知Web服务发现机制

随着提供相同功能的Web服务数量的日益增多,服务质量(Quality of Service,QoS)成为用户选择Web服务的重要考虑因素.目前,通过对服务QoS属性在语法层匹配来提供Web服务选取的机制不能很好地满足复杂QoS属性匹配的要求.研究了基于用户QoS需求偏好,将用户需求的QoS与候选服务的QoS进行语义比较,结合约束规划(Constraint Programming)方法,在语义层匹配Web服务的QoS属性,选取满足匹配要求的服务,最后对满足QoS属性值约束的候选服务进行优化选择处理,获取最终匹配的候选服务.     

NGI中一种基于食物链算法的柔性QoS组播路由算法

针对下一代互联网（Next Generation Internet,NGI）难以精确测量和用户服务质量（Quality of Service,QoS）需求难以完全表达的特点,设计了一种基于食物链算法（Food Chain Algorithm,FCA）的柔性QoS组播路由算法。给出了QoS组播路由问题模型及其数学描述,针对NGI中QoS参数信息不精确和用户需求柔性的特点,通过博弈分析确定用户和网络方在边上的效用能否达到Nash均衡,基于模糊数学的相关知识并结合FCA的寻优能力,找出在给定条件下用户效用、网络方效用和满足用户QoS需求的可信度同时达到最大的组播路由树。对算法进行了仿真实现与性能评价,结果表明,它是可行和有效的。     

基于组织进化的ABC支持型单播路由机制

提出一种支持总最佳连接ABC(Always Best Connected)的服务质量QoS(Quality of Service)单播路由机制.该机制采用区间形式刻画用户QoS需求和网络链路参数;引入偏好序列,以满足用户对不同类型网络的偏爱;引入概率密度函数、满意度函数和评价函数,以精确测量网络链路参数值和准确表达用户QoS需求;引入成本、价格、费用和博弈机制,兼顾用户和网络提供方利益;基于组织进化算法OEA(Organizational Evolutionary Algorithm),寻找使各方效用达到或接近Nash均衡下Pareto最优的QoS单播路径.仿真结果表明,该机制是可行和有效的.     

基于灰色关联分析的Web服务选择

为方便用户选择最优Web服务,利用灰色系统理论对Web服务质量QoS属性因子进行分析,提出了一种基于用户QoS偏好的Web服务灰色关联分析方法。考虑到Web服务QoS的不确定性,该方法使用区间对Web服务QoS值进行建模。为了确定候选服务的QoS与用户QoS需求的符合程度,先针对服务的每个QoS属性,计算其与用户QoS需求的灰色区间关联系数;然后结合各个QoS属性的关联系数计算候选服务的QoS与用户QoS需求的综合灰色区间关联度,关联度越大的服务越符合用户的要求;最后从满足用户功能需求的Web服务中选择灰色关联度最大的Web服务推荐给用户。与其它Web服务评价模型相比较,该模型更加符合Web服务QoS的实际情况,能够在服务QoS信息不充分、不确定的环境下,对QoS属性进行合乎实际的分析处理,从而得到更加合理有效的QoS评价。     

基于OpenFlow的自适应QoS流量控制方法设计与实现

随着新型业务类型如视频会议、网络游戏、交互应用等不断涌现,如何利用有限的网络资源进行有效的流量控制,以保障业务的服务质量(Quality of Service,QoS)已成为一个非常迫切的问题。而目前已有的QoS流量控制方法大多存在着对网络资源的利用率低、可靠性差、粒度粗、实现困难,可扩展性差等问题。软件定义网络(Software Defined Network,SDN)提出的控制层与数据层分离思想,为解决此类问题提供了崭新的思路。本文提出了一种基于OpenFlow技术的QoS流量控制方法,利用自适应多约束QoS路由技术,提高了QoS控制的灵活性与可靠性,实现了对网络资源的高效利用和业务流控制的细粒度。最后,我们在OpenvSwitch环境下验证了该方法的有效性。     

M-GREEN: An active queue management mechanism for multi-QoS classes

This paper proposes a QoS active queue management (AQM) mechanism for multi-QoS classes, named as M-GREEN (Global Random Early Estimation for Nipping), which includes the consideration of QoS parameters and provides service differentiation among different flows/classes. M-GREEN extends the concept of “Random” and “Early Detection” in RED to “Global Random” and “Early Estimation,” respectively. Furthermore, M-GREEN extends the “linear” concept of RED to an “exponential” one to enhance the efficiency of AQM. For performance evaluation, extensive numerical cases are employed to compare M-GREEN with some popular AQM schemes and to show the superior performance and characteristics of M-GREEN. Consequently, M-GREEN is a possible way to provide the future multimedia Internet with differential services for different traffic classes of diverse QoS requirements.     

Generalized processor sharing: Characterization of the admissible region and selection of optimal weights

We consider a two-class Generalized Processor Sharing (GPS) queueing system, in which each class has its specific traffic characteristics and quality-of-service (QoS) requirements. Traffic of both classes is assumed to be Gaussian (a versatile family of models that covers both long-range dependent and short-range dependent traffic). In this paper we address the question how to select the GPS weight values. To do so, we first characterize the admissible region of the system for fixed weights. Then we obtain the realizable region by taking the union of the admissible regions over all possible weight values. The results indicate that, under a broad variety of traffic characteristics and QoS requirements, nearly the entire realizable region can be obtained by strict priority scheduling disciplines. In addition, we indicate how the buffer thresholds, QoS requirements and the traffic characteristics of the two classes determine which class should get high priority.     

A QoS Multicast Routing Algorithm Working with Imprecise State Information

In large networks, maintaining precise global network state information is almost impossible. Many factors, including non-negligible propagation delay, infiequent link state update due to overhead concerns, link state update policy, and hierarchical topology aggregation, have impacts on the precision of the network state information. The existing QoS multicast routing algorithms do not provide satisfactory performance with imprecise state information. In this paper, we propose a distributed QoS multicast routing scheme based on traffic lights, called QMRI algorithm, which can probe multiple feasible tree branches, and select the optimal or near-optimal branch through the UR or TL mode for constructing a multicast tree with QoS guarantees if it exists. The proposed algorithm considers not only the QoS requirements but also the cost optimality of the multicast tree. Extensive simulations show that our algorithm achieves high call-admission ratio and low-cost multicast trees with modest message overhead. The algorithm can tolerate high degree of state information imprecision.     

FIAC: a resource discovery-based two-level admission control for differentiated service networks

Differentiated Service (DiffServ) architecture has been proposed as a scalable QoS architecture for Internet. DiffServ, however, could not control its loads under heavy traffic conditions, and it could not provide strong QoS responses for individual traffic flow. This paper introduces at the edges of a DiffServ domain, a novel two-level admission control scheme, the Fair Intelligent Admission Control (FIAC). At per-class level, FIAC admits traffic according their fairshare and usage while preventing possible congestion within the DiffServ core. At per-flow level, FIAC estimates and allocates the fairshare for each flow within a class.

Simulation results demonstrate that FIAC adheres extremely well to the bandwidth requirements of DiffServ classes while preventing congestion within the DiffServ core. With FIAC's per-flow level enabled, FIAC is able to prevent uncontrolled UDP flows from depriving TCP-controlled flows of bandwidth share when they are aggregated to the DiffServ domain.     

Two efficient packet aggregation mechanisms and QoS support in a slotted dual bus optical ring network

In this paper, a novel approach for efficiently supporting IP packets directly into a slotted optical wavelength-division-multiplexing (WDM) layer with several quality of service (QoS) requirements is presented and analyzed. The approach is based on two main features. First, an aggregation cycle is performed at fixed time intervals by assembling several IP packets into a single macro-packet of fixed size, called an aggregate packet. Second, since IP packets have variable size, the aggregation process may allow or not the segmentation of an IP packet if it does not fit into the remaining gap in the aggregate packet. As a key element of our proposition, an efficient QoS support access mechanism is presented. The new QoS control performs aggregation in a loop manner by always beginning the aggregation cycle with the highest priority class. The aggregation cycle ends if the aggregate packet cannot accommodate more IP packets, or if the lowest priority class is reached. We introduce two analytical models that allow us to evaluate the effectiveness of the aggregation technique with and without segmentation. On the other hand, a third analytical model is presented to analyze the standard case (where no aggregation is performed), and comparisons between the three models are carried out. The aggregation models are validated by simulations, and the effect of self-similarity is also analyzed. The application of the proposed approach takes place in a slotted dual bus optical ring network (SDBORN), where we prove that a good fairness and high bandwidth efficiency are achieved, and that only two QoS classes (real-time and non-real-time classes) at the access interface (IP domain) are sufficient in order to fulfill the strict delay requirements of real-time data traffic.     

Performance analysis of adaptive buffer management mechanism using autoregressive based MPEG-4 encoded video traffic model

The burstiness of video traffic in future wired and wireless networks makes dynamic management of network resources more critical. This helps to meet stringent delay and loss requirements of video traffic and improves its Quality of Service (QoS). Since buffer management in queueing system plays an important role towards effective control of QoS for various types of applications, we have focused on its dynamic management. In this paper, we have proposed ADPBS scheme for priority queueing system. The performance of this scheme is analyzed with MPEG-4 encoded video sequence as input to the ADPBS queue. The simulation is carried out in MATLAB for various combinations of threshold control parameters, different traffic load and input traffic mix variations. The results of simulations indicate that dynamically controlled threshold in ADPBS contributes to significant reduction of packet loss of different priority classes as compared with static partial buffer sharing queue and first in first out queue based on threshold control parameters and the traffic type.     

Providing traffic smoothness and service guarantees within ATM networks through a rate-controlled service discipline

With the introduction of diverse rate requirements under a variety of statistical multiplexing schemes, traffic burstiness behavior of a source stream and its quality-of-service (QoS) performances within the ATM networks become difficult to model and analyze. In this paper, we address this issue and propose a rate-controlled service discipline that provides control of the traffic burstiness while maintaining QoS guarantees for traffic flows with various rate requirements. According to our analysis, traffic streams from different connections can be well regulated at the output of each network node based on their rate requirements. Traffic envelope and the associated burstiness behavior inside the network can thus be effectively characterized. In addition, by assuming a leaky-bucket constrained input source, we prove that the proposed scheme can provide end-to-end delay and jitter bounds for each connection passing through a multi-hop network. Further, due to the low traffic burstiness, only a small buffer space is required at the internal switches for guaranteeing QoS requirements.     

由VTRR算法为DiffServ提供QoS的一种方法

DiffServ是解决宽带Internet QoS控制的一种可行方案,它在边界节点将不同的QoS要求映射成PHB.对每类具有相同PHB的IP业务流,应用VTRR公平调度算法.VTRR算法允许在竞争带宽的业务流中公平共享分配的带宽.将VTRR与RSVP结合使用,能为DiffServ提供QoS保证.     

Dynamic bandwidth allocation for 3G wireless systems—A fuzzy approach

3G Wireless systems are to support multiple classes of traffic with widely different characteristics and quality of service (QoS) requirements. A major challenge in this system is to guarantee the promised QoS for the admitted users, while maximizing the resource allocation through dynamic resource sharing. In the case of multimedia call, each of the services has its own distinct QoS requirements concerning probability of blocking (P_B), service access delay (SAD), and access delay variation (ADV). The 3G wireless system attempts to deliver the required QoS by allocating appropriate resources (e.g. bandwidth, buffers), and bandwidth allocation is a key in achieving this. Dynamic bandwidth allocation policies reported so far in the literature deal with audio source only. They do not consider QoS requirements. In this work, a fuzzy logic (FL)-based dynamic bandwidth allocation algorithm for multimedia services with multiple QoS (P_B, SAD, ADV, and the arrival rate) requirements are presented and analyzed. Here, each service can declare a range of acceptable QoS levels (e.g. high, medium, and low). As QoS demand varies, the proposed algorithm allocates the best possible bandwidth to each of the services. This maximizes the utilization and fair distribution of resources. The proposed allocation method is validated in a variety of scenarios. The results show that the required QoS can be obtained by appropriately tuning the fuzzy logic controller (FLC).