基于主动网络的RSVP体系结构设计

IP网络新的应用对网络的服务质量(QoS)提出了新的不同的要求,因此必须在现有的“尽力服务”机制的基础上提供服务质量管理机制。在对QoS进行分析的基础上,提出了一种新的QoS体系结构,即基于主动网络的QoS体系结构,并结合IntServ QoS模型,提出了支持RSVP协议动态部署的主动节点的模型。     

Ad hoc网络多径带内信令系统的研究与实现

无线Ad hoc网络中带宽资源有限，研究如何给用户提供QoS保证很有意义。以带内信令系统INSIGNIA和多径源路由MSR为基础，提出了一种适合于Ad hoc网络的QoS保证机制，即M—INSIGNIA，并且用NS(Network Simulation)网络仿真软件设计实现了针对此机制的一个仿真实验，通过大量的实验证明M—INSIGNIA对QoS支持更有效。     

主动网络的服务质量体系研究

主动网络作为一种可编程(可定制)网络,其安全性和网络性能是关注的焦点.文章从主动网络的QoS需求出发,提出了支持QoS的主动节点结构,讨论了QoS部署策略以及服务质量协商模式.     

一种新的QoS约束的多播路由协议

网络技术和多媒体技术的发展使得未来的Internet对具有QoS(Quality of Service)需求的多播应用的支持变得更加迫切．为了解决现有QoS多播路由协议消息复杂度高、寻路成功率低以及连接建立时间比较长等问题，作者提出了一种新的QoS多播约束路由协议MRPQoS(Multicast Routing Protocol with QoS constraints)．它完全分布式运行，将局部搜索与全局搜索、单分支搜索与多分支搜索有机地结合在一起，较好地解决了上述问题．仿真结果证明：MRPQoS较其它协议更适合于网络状态变化比较频繁的环境以及实时多媒体应用．     

SDN/OSPF混合网络中一种智能QoS感知流量转发方案

针对SDN/OSPF混合工业网络中某些关键任务不能满足服务质量(QoS)的要求,造成网络拥塞、端到端延迟大、可靠性较低的问题,提出了一种智能QoS感知流量转发(Intelligent QoS-aware Traffic Forwarding,IQTF)策略.设计了一种新的拓扑发现方案来获得软件定义网络(Software...     

基于MPLS Diff-Serv的QoS实现技术

IP网络对服务质量(QoS)的支持一直是网络技术研究的热点,有几种协议支持IP网络的QoS,描述了综合服务结构模型(IntServ／RSVP)、区分服务结构模型(Diff-Serv)和多协议标记交换技术(MPLS)的原理,讨论了Diff-Serv的关键技术和基于MPLS Diff-Serv支持数据传输服务质量(QoS)的实现技术。     

无线传感器网络中基于Agent的QoS管理机制

针对无线传感器网络的节能特性和网络应用对服务质量(QoS)要求的不断提高,提出了一种节能高效的服务质量管理机制,运用Agent技术实现传感器节点的信息采集和QoS预约,当网络环境变化时进行QoS协商与再协商.与传统QoS机制相比,基于Agent实现的QoS管理机制能够最大限度对支持网络应用,更适合传感器网络的节能要求,延长网络的生命期.     

一种新的QoS感知的Ad Hoc网络多径DYMO路由协议

DYMO是Ad Hoc网络中一种动态的按需路由协议,本质上属于单径路由协议,而多径路由能更好地支持QoS。首先分析了DYMO协议的优点及存在的问题,在此基础上将DYMO和服务质量QoS及多径路由结合起来,提出一种新的QoS感知的多径DYMO路由协议QA-DYMO,利用多条链路不相交路径来发送数据,并提出一种QoS感知的路由算法。该协议能够适应网络的动态变化和较好地支持QoS。仿真结果表明,该协议要优于其他相关的协议。     

基于Ad Hoc多QoS约束的多播路由协议

针对移动Ad Hoc网络特点，研讨了Ad Hoc网络中其有多QoS约束的多播路由问题，其中主要包含延迟、延迟抖动、带宽、代价等QoS约束。描述了一种适应于研究Ad Hoc网络QoS多播路由的网络模型，提出了Ad Hoc网络中一种具有多QoS约束的多播路由协议。给出了MQAP的路由实现过程，进行了正确性证明和复杂性分析。仿真实验结果表明，MQAP为Ad Hoc网络多QoS约束多播路由提供了一种新的有效途径。     

QoS路由浅析

随着用户对多媒体应用需求的不断增加，几种新的网络体系结构也随之产生，如ATM(异步传输模式)网络就是以固定长度的信元 为最小传输单位来减少时延，以满足对实时性要求较高的视频和音频的需要。然而QoS路由作为支持多媒体应用的一个很重要的技术在这些体系结构中还没有涉及到。该文讨论了QoS路由的一些问题。首先讨论了QoS路由中最基本的问题，也就是说，从源端到目的端，找到一条满足各种限制的一条路径，使这条路径能满足特定应用的QoS方面的需要。最后，对于基于源地址的路由给出了一种路径计算算法。     

QuCOM:一种面向构件系统的QoS管理模型

在性能变化不确定的系统内,不同的应用处于竞争和共享有限的系统资源、并受其变化影响的环境中．在系统运行时,对于需要QoS保证的应用,为保证其QoS属性,应能适应于这种环境．考虑到系统资源的全局管理特性,仅从应用中增加适应机制是不够的,还需在系统层中增加QoS管理机制．为此,给出了一种面向构件系统的QoS管理模型——QuCOM（quality component）及其集成到系统构件框架的方法,使基于QuCOM开发的构件应用能够适应于变化的系统环境,并为了验证QuCOM的有效性,以一个视频流应用为例,给出了相关实验数据分析．     

Adaptive Quality of Service Support for Packet-Switched Wireless Cellular Networks

In this paper, we propose an adaptive quality of service (QoS) design approach via resource reservation and rate adaptation to support multimedia over wireless cellular networks. Three contributions of this work are: (a) an adaptive QoS model that seeks to provide QoS assurances within bounds for each packet flow and to make advance resource reservation in order to support seamless mobility, (b) a revenue-based resource adaptation design that seeks to maximize network revenue while satisfying the QoS requirements, and (c) a resource reservation protocol that supports both application-initiated resource reservation and network-initiated resource adaptation. Our initial implementation and measurements confirm the effectiveness of the proposed design.     

Specification,Mapping and Control for QoS Adaptation

In this paper we describe a fuzzy-control approach for quality of service (QoS) adaptation, needed in distributed multimedia applications. QoS adaptation is necessary (a) due to sudden variations in network resource availability, especially in the case of Internet, and (b) due to multiple applications requiring shared resource such as bandwidth. To solve the problem of QoS adaptation, several sub-problems need to be considered: (1) mapping of user perception and different combinations of application QoS values onto a uniform quality metric, (2) estimation, control and adjustment of application QoS parameters in case of network and other resource congestion, and (3) enforcement algorithm which reacts according to adapted QoS parameters. Our approach is to solve the QoS adaptation using the integration of (a) quality degree function, which maps the application QoS parameters into a metric, called quality degree, (b) fuzzy controller, which controls, estimates and adjusts the application QoS parameters according to resource availability, and (c) filter algorithms, which are the services to enforce the adapted QoS parameters. The quality degree function associates quality degree as the quality measure with different combinations of application QoS values. This function is influenced by the users perception of quality. The fuzzy control takes the results of the quality degree function, estimates the new quality degree and its corresponding quality level, predicts the new application QoS parameters, and adjusts them. The results of the adapted QoS parameters are then used by the filter algorithms to enforce the changes, proposed by the fuzzy controller, by allocating bandwidth to the application according to its QoS parameter values. We have implemented and applied the quality degree function, the fuzzy controller, and the filter algorithms to the video distribution system (VDS). The results of VDS over the local area network show that (1) the target system improves user perceived QoS at the receivers, and (2) the bandwidth utilization increases significantly when using our fuzzy-control approach for QoS adaptation.     

An Approach to Quality of Service Management in Distributed Multimedia Application: Design and an Implementation

Most work related to quality of service (QoS) is concerned with individual system components, such as the operating system or the network. However, to support distributed multimedia applications, the entire distributed system must participate in providing the guaranteed performance levels. In recognition of this, a number of QoS architectures have been proposed to provide QoS guarantees. The mechanisms and schemes proposed by those architectures are used in a rather static manner since the involved entities, e.g., the network, sender and receiver, are known before the connection (call) set-up phase. In contrast to these architectures, we propose a general QoS management framework which supports the dynamic choice of a configuration of system components to support the QoS requirements for the user of a specific application. We consider different possible system configurations and select the most appropriate one depending on the desired QoS and the available resources. In this paper we present an overview of this general framework; especially, we concentrate on QoS negotiation and adaptation mechanisms. To show the feasibility of this approach, we designed and implemented a QoS manager for distributed multimedia presentational applications, such as news-on-demand. The negotiation and adaptation mechanisms which are supported by the QoS manager are specializations of the general framework. The proposed framework allows to improve the utilization of system resources, and thus to increase the system availability; it also allows to recover automatically, if this is possible, from QoS degradations. Furthermore, it provides the flexibility to incorporate different resource reservation schemes and scheduling policies, and to accommodate new system component technologies.     

Enabling QoS adaptation decisions for Internet applications

We present a network model that allows processing of QoS (quality of service) information about media flows to enable applications to make adaptation decisions. Our model is based around a multi-dimensional spatial representation that allows QoS information describing the flow constructions and QoS parameters – flow-states – to interact with a representation of the network QoS. The model produces reports about the compatibility between the flow-states and the network QoS, indicating which flow-states the network can currently support. The simple nature of the reports allows the application to make decisions, dynamically, on which flow-state it should use. The model is relatively lightweight and scaleable. We demonstrate the use of the model by simulation of a dynamically adaptive audio tool. Our work is ongoing.     

A formal approach to adaptive software: continuous assurance of non-functional requirements

Modern software systems are increasingly requested to be adaptive to changes in the environment in which they are embedded. Moreover, adaptation often needs to be performed automatically, through self-managed reactions enacted by the application at run time. Off-line, human-driven changes should be requested only if self-adaptation cannot be achieved successfully. To support this kind of autonomic behavior, software systems must be empowered by a rich run-time support that can monitor the relevant phenomena of the surrounding environment to detect changes, analyze the data collected to understand the possible consequences of changes, reason about the ability of the application to continue to provide the required service, and finally react if an adaptation is needed. This paper focuses on non-functional requirements, which constitute an essential component of the quality that modern software systems need to exhibit. Although the proposed approach is quite general, it is mainly exemplified in the paper in the context of service-oriented systems, where the quality of service (QoS) is regulated by contractual obligations between the application provider and its clients. We analyze the case where an application, exported as a service, is built as a composition of other services. Non-functional requirements—such as reliability and performance—heavily depend on the environment in which the application is embedded. Thus changes in the environment may ultimately adversely affect QoS satisfaction. We illustrate an approach and support tools that enable a holistic view of the design and run-time management of adaptive software systems. The approach is based on formal (probabilistic) models that are used at design time to reason about dependability of the application in quantitative terms. Models continue to exist at run time to enable continuous verification and detection of changes that require adaptation.     

Application-level QoS control for video-on-demand

User requirements and device heterogeneity call for Web services with differentiated quality of service (QoS). In particular, services with response-time constraints, such as video-on-demand (VoD), require the differentiation, control, and dynamic adaptation of QoS. Service providers and network operators need methodologies and mechanisms for managing runtime QoS. Using mobile agent technology, the ubiQoS middleware supports QoS tailoring and adaptation of video-on-demand flows in response to user preferences and terminal properties. The design, implementation, and deployment of QoS-aware Internet services can significantly benefit from a middleware approach at the application level. Our experimental results show the feasibility of application-level middleware solutions based on code mobility for Internet VoD services with differentiated QoS.     

基于服务质量水平的带宽分层自适应

自适应服务质量技术能有效地适应随时间变化的网络环境.提出了基于服务质量水平max-mi n公平的带宽分层自适应模型.此模型建立在应用层和网络层自适应控制的机制上.网络层利 用资源探测协议来实现基于服务质量水平max-min公平的带宽分配,而应用层实现特定于应 用的自适应服务.     

Joint optimisation of application QoS and energy conservation in grid environment

Mobile and wireless devices with limited energy are now of interest for the grid community. Reducing the related energy consumption is very important for wireless devices. Compared to conventional grid systems, energy aware grids need to support application quality of service (QoS) with limited energy. There is an inherent conflict in the design goals for high grid application QoS and low energy consumption. To address this challenging problem, this article considers joint optimisation of application QoS and energy conservation in grid environment. Joint optimisation of application QoS and energy conservation is targeted to maximise the system utility without exceeding the deadline and the total energy available, which can be provided by an exhaustible source such as a battery. This article formulates joint optimisation of application QoS and energy conservation as constrained maximisation problem; the constraints include energy budget and application QoS requirements. This article also presents a QoS and energy aware scheduling algorithm (QESA) which balances application QoS and energy conservation to improve system performance. In the simulation, the performance evaluation of QESA is conducted.     

Towards an ideal service QoS in fuzzy logic-based adaptation planning middleware

Mobile applications require an adaptation phase to adapt to the user's and application context. Utility functions or rules are most often used to make the adaptation planning or decision, i.e. select the most adapted variant for each required service. Fuzzy controllers are used when it is difficult or even impossible to construct precise mathematical models. In the case of mobile applications, the large number of Quality of Service (QoS) and context parameters causes an exponential increase in the number of rules (aka. rule explosion problem), that increases the processing time of the adaptation planning. To reduce the processing time and simplify the fuzzy control system, we propose the concept of ideal QoS. Fuzzy values of ideal QoS parameters are calculated using several fuzzy control systems to fit the context state and user preferences. A fuzzy logic similarity metric based on fuzzy sets and fuzzy operators is proposed to select the service variant having the nearest QoS values to the ideal. Experiments show that our approach can significantly improve both the number of rules and the processing time when selecting the variant that well adapts to environment changes.