Provide Service Differentiation Research Articles

Distributed TXOP Allocation Scheme in IEEE 802.11e Wireless LANs

Multimedia traffic is expected to be one of the most important traffic types in wireless LANs. However, multimedia traffic is very sensitive to delay so that the traffic has to be transmitted to receivers within its delay bound. The IEEE 802.11e EDCA (Enhanced Distributed Channel Access) defines a TXOP (Transmission Opportunity) parameter to provide service differentiation and QoS (Quality of Service) of the traffic. A station can continuously transmit multiple packets for the duration of a TXOP. When stations support multimedia applications with different QoS requirements, fairness problem occurs. In order to alleviate the fairness problem, we propose a distributed TXOP allocation scheme based on the delay bound. In the proposed scheme, a station checks the delay bound of each data packet in the queue, and allocates its TXOP value to guarantee the delay bounds of all the packets in the queue. Simulation results show that the proposed scheme outperforms other TXOP allocation schemes.

A distributed controller for a virtualized router

Abstract In this paper, a distributed controller for a virtualized router is proposed. This controller enables the dynamic and automatic resource allocation between the different virtual routers (called slices) running on top of the physical router. The controller is designed on a two-layer architecture. A slice controller (one for each slice) estimates the relationship between the past performances and resource allocations of the slice using a linear model, and then determines the requested allocation for the slice to meet its target performance. The physical router consists of a set of modular linecards. A resource controller (one for each linecard), collects the resource allocation requests from the different slices using the resources it controls and determines the allocations based on the available capacities of the resources. Resources are allocated to slices to guarantee their target performances if possible, or provide service differentiation if the total requests from all the slices exceeds the capacities of the shared resources. We have found that the convergence of the controller depends on different parameters (such as the number of slices and the parameters of the linear model) and therefore some tuning of these parameters is needed for the system to achieve the stability.

An analytical model for the performance evaluation of multistage interconnection networks with two class priorities

The aim of this paper is to develop an analytical method for performance evaluation of double prioritized Multistage Interconnected Networks (MINs) with single or multilayers and backpressure operation which provide service differentiation and QoS guarantee to an end application running over next generation Internet or Grid systems. Specifically, a new architecture of switching elements is used for the construction of MINs. This switch element uses two parallel queues in order to serve dual priority traffic. Besides this, uniform traffic conditions are presupposed and the bulk of packet arrivals in each cycle to the network inputs follow a Bernoulli distribution. A new analytical model for evaluating single buffered MIN’s with 2×2 special switching elements supporting internally two classes’ priority traffic is presented. Equations for the steady state are derived. These equations are then used in finding the most important multistage network performance metrics, such as throughput, and packet latency. The results are also validated using simulation and compared with previous related work in marginal cases. This proposed analytical model is accurate for various network sizes and various values of offered traffic to the multistage network inputs.

Autonomic Placement of Mixed Batch and Transactional Workloads

To reduce the cost of infrastructure and electrical energy, enterprise datacenters consolidate workloads on the same physical hardware. Often, these workloads comprise both transactional and long-running analytic computations. Such consolidation brings new performance management challenges due to the intrinsically different nature of a heterogeneous set of mixed workloads, ranging from scientific simulations to multitier transactional applications. The fact that such different workloads have different natures imposes the need for new scheduling mechanisms to manage collocated heterogeneous sets of applications, such as running a web application and a batch job on the same physical server, with differentiated performance goals. In this paper, we present a technique that enables existing middleware to fairly manage mixed workloads: long running jobs and transactional applications. Our technique permits collocation of the workload types on the same physical hardware, and leverages virtualization control mechanisms to perform online system reconfiguration. In our experiments, including simulations as well as a prototype system built on top of state-of-the-art commercial middleware, we demonstrate that our technique maximizes mixed workload performance while providing service differentiation based on high-level performance goals.

High-throughput differentiated service provision router architecture for wireless network-on-chip

This paper proposes a QoS-aware wireless network-on-chip architecture that not only enables quality-oriented network transmission with a feasible implementation overhead but also maintains well-balanced workload inside the hybrid networks to enhance system throughput. Transmission differentiation allows guaranteed service provision and realises network resource optimisation. The advanced routers employ congestion management which first grants high priority packets from more congested areas and then directs them to paths without contention. Adaptive load-balanced routing effectively relaxes congestion situations and prevents networks from worse contention. Simulation results show that average latency of high priority is significantly improved. Flexible buffer management further improves transmission performance and resource utilisation efficiency. The generality for the proposed router architecture has been demonstrated from various traffic patterns. Feasibility evaluation shows negligible cost overhead and demonstrates its practicality.

QoS for wireless sensor networks: Enabling service differentiation at the MAC sub-layer using CoSenS

Providing service differentiation in wireless sensor networks while proposing simple and highly scalable solution is a challenging problem. We retain the use of CSMA/CA as access protocol because of its simplicity, versatility and good scalability properties. We developed CoSenS, a Collect then Send burst Scheme, on top of it to address its weaknesses while facilitating the implementation of scheduling policies. In this article, we propose a simple and scalable service differentiation solution; we implement fixed priority and earliest deadline first on top of CoSenS. The simulation analysis shows that our solution self-adapts to the traffic variation and greatly enhances end-to-end delay, reliability and deadline meet ratio for urgent traffic while not degrading best effort traffic compared to IEEE 802.15.4 original protocol and IEEE 802.15.4 implementing these scheduling policies. Additionally, CoSenS is implemented and tested on motes. The real experimentation results validated our simulation analysis.

Performance Optimization for IEEE 802.11 with QoS Differentiation Supporting

PDF HTML阅读 XML下载 导出引用 引用提醒 IEEE 802.11支持QoS区分服务的性能优化 DOI: 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: Supported by the National Natural Science Foundation of China under Grant No.60802024 (国家自然科学基金); the National High-Tech Research and Development Plan of China under Grant Nos.2005AA123820, 2005AA121122 (国家高技术研究发展计划(863)) Performance Optimization for IEEE 802.11 with QoS Differentiation Supporting Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:基于IEEE 802。11 p-persistent协议模型的研究，对一种近似优化条件在多优先级业务网络条件下的适用性进行了证明。应用该近似优化条件，提出了一种适用于IEEE 802。11 QoS区分服务支持的自适应优化算法QATC (QoS-supporting adaptive transmission control)。算法利用信道侦听信息实时优化调整各优先级业务的发送概率，更新相应的协议参数，实现信道利用率的提高和系统性能的增强。QATC算法不需要估计各优先级业务的节点数量，并且拥有 Abstract:In this paper, the extended application of an approximating optimization formula, which is first proposed to simplify the optimization of networks with a single traffic class in the literature, in QoS-supporting networks is analytically justified and numerically investigated. Based on the formula, an adaptive optimization scheme, named QATC (QoS-supporting adaptive transmission control), is proposed for IEEE 802.11 to optimize the system performance, while providing service differentiation among traffic classes. The proposed scheme works around the difficult station number estimation. It utilizes information acquired from channel sensing to adjust the packet transmitting, adaptively towards achieving an invariable system object for different network conditions. Furthermore, the scheme to optimize the multi-rate networks is also exploited. Simulation results show that QATC has an effective ability to optimize the operation of networks adaptively in various conditions, and it can greatly improve the system throughput compared with the standard IEEE 802.11 MAC and related enhancements. Moreover, the system throughput, achieved by the scheme, is very close to the theoretical optimal value. 参考文献 相似文献 引证文献

High-Priority First Transmission to Efficiently Support Service Differentiation in Just-in-Time OBS Networks

The provision of service differentiation is an important aspect that has to be considered for the definition of next-generation networks due to the high heterogeneity of the traffic that will dominate networks in the near future. This is particularly important in the context of optical burst switching, which is emerging as one of the strong candidate technologies for the next-generation optical Internet. Preemptive contention resolution schemes are very effective solutions for providing service differentiation in such networks; however, they cannot be applied together with the just-in-time signaling protocol because of the great loss in efficiency in terms of wavelength utilization and maximum achieved throughput that results when the number of preemptions becomes too large. This paper presents a preemption-based service differentiation solution that is suitable for the just-in-time optical burst switching paradigm because it keeps the preemption probability (i.e., the probability of observing a preemption when a contention occurs) low. Within the proposed technique, bursts are created at their ingress node and combined into chains, arranging them in order of decreasing priority. Then, a conventional preemption scheme is adopted at core nodes to handle contentions. An analytical study is presented and some traffic scenarios are analyzed by simulation to evaluate the performance of the proposed method.

MDP-based lightpath establishment for service differentiation in all-optical WDM networks with wavelength conversion capability

In this paper, we propose a service differentiation method for lightpath establishment in all-optical WDM networks. The proposed method derives the optimal lightpath establishment policy for each serve class based on a Markov Decision Process (MDP). The optimal policy considered here is to provide service differentiation for lightpath establishment and to utilize wavelengths effectively. Here, we focus on two cases for wavelength conversion capability; full-range wavelength conversion and limited-range wavelength conversion. For full-range wavelength conversion, the number of lightpaths for each class is considered as a state of MDP. On the other hand, for limited-range wavelength conversion, the service class of lightpath that has been established with each output wavelength is considered as the state. Based on these states, we derive the optimal policy for lightpath establishment. In both cases, we evaluate the performance of the proposed method with simulation. In numerical examples, we show that our proposed method can provide service differentiation and use wavelengths effectively regardless of wavelength conversion capability.

Quality of experience-driven adaptation scheme for video applications over wireless networks

User's perceived quality of service (QoS) or quality of experience (QoE) is likely to be the major determining factor in the success of new multimedia applications over wireless/mobile networks. The primary aim of this study is to present an adaptation scheme that is QoE-driven for optimising content provisioning and network resource utilisation for video applications over wireless networks. The proposed scheme encompasses the application of a QoE-driven model for optimising content provisioning and network resource utilisation. The content provisioning is optimised by the determination of initial content quality by adapting the video sender bitrate (SBR) according to users' QoE requirement. By finding the impact of the QoS parameters on end-to-end perceptual video quality, the optimum trade-off between SBR and frame rate is found and the benefits to network providers in maximising existing network resources are demonstrated. The QoE is measured in terms of the mean opinion score. The proposed scheme makes it possible for content providers to achieve optimum streaming (with an appropriate SBR) suitable for the network and content type for a requested QoE. The scheme is also beneficial for network providers for network resource provision and planning, and therefore maximising existing network infrastructure by providing service differentiation.

Research of the QoS-Supporting IEEE 802.11 EDCA Performance

With the rapid development of wireless applications, the IEEE 802.11 task group proposed the QoS- supporting enhanced distributed channel access (EDCA) MAC mechanism, which is based on the legacy IEEE 802.11 DCF, to provide service differentiation for different types of traffic flows in the networks. This paper proposes a novel Markov chain-based analytical model for the IEEE 802.11 EDCA. Unlike the existing analytical models for the EDCA, the proposed model incorporates all the three major features of the EDCA, i.e., Wmin/Wmax, AIFS (arbitration inter-frame space), and TXOP (transmission opportunity). With this model, the paper presents the performance evaluations of the EDCA analytically, including each priority’s transmission throughput, media access delay, packet loss rate, etc. It dose not only analyze the saturated EDCA operation case, but also analyze the non-saturated EDCA operation case. Simulation results confirm the accuracy of the model analysis. Based on the model analysis, this paper proposes an admission control scheme D-TXOP (dynamic TXOP). While making admission decision, the scheme adjusts different priorities’ TXOP parameter settings adaptively according to their QoS requirements, which greatly enhances the network capacity.

Service differentiation using priority-based MAC protocol in MANETs

Multihop wireless network has emerged recently as an evolution of wireless network technology and is likely to be the integral part of future communication environment. In this context, support for quality of service (QoS) is becoming an inherent necessity, rather than an additional feature of the network. In this paper, we propose a priority-based variant of the IEEE 802.11 DCF for providing service differentiation at the MAC layer of MANETs. The channel access priorities are realised with a backoff timer selection scheme. Further, differentiating relayed traffic from self-generated traffic, improves both end-to-end QoS performance and overall network utilisation in multihop environments. A priority-based queue management and packet scheduling is implemented to improve the intra-node service differentiation. Performance analysis for single hop scenarios is done using a Markov chain model whose accuracy is validated through simulation. Furthermore, simulation studies in multihop scenarios show suitability of the proposed scheme to provide an enhanced level of service differentiation.

PARADOX OFMARKETINGTOTHE PHYSICALLYCHALLENGED INDIVIDUALS - SUSTAINABLE DIFFERENTIATION OR SIMPLY MARKETING HYPE

It has long been acknowledged that service differentiation through effective market segmentation ensures survivability of the firm in the long run. While voluminous studies on segmentation and providing service differentiation were conducted, little previous research work was done in the context of the airline industry. It is the intention of this paper to examine the needs of the physically challenged individuals and the reasons constraining the industry in fulfilling these needs. This paper will contribute significantly to understanding the needs of the physically challenged individuals and suggest that meeting the needs of these individuals provide sustainable competitive advantage for those who dare to adapt their strategy. Given the little previous researches were conducted in the identification of this potential group of customers, it is no wonder the airline industry is myopic and ill-prepared in meeting the needs of this viable group of customers. This study is also beneficial from a managerial perspective given the implications in assisting the airline operators and marketers to better understand this group of customers and their needs. Particularly specific features identified in this paper can help increase the overall position of airline operators that would appeal to this growing segment.

Providing forwarding assurance in multi-hop wireless networks

The Assured Forwarding (AF) service in a differentiated services network offers different levels of forwarding assurance for IP packets. In the wired Internet, the AF service is implemented as a queue management scheme associated with a drop policy in each router. In multi-hop wireless networks, however, queue management in each node is not enough to provide service differentiation globally since resource is shared among neighboring nodes. Hence, several studies for the AF service in wireless networks have proposed to manipulate the contention window size to provide service differentiation. The contention window size based differentiation scheme provides the AF service by transmitting packets in a higher class with a smaller contention window. However, since network congestion in multi-hop wireless networks causes packet losses at the link layer, the contention window size based differentiation scheme is not sufficient to provide the AF service. In this paper, we propose a rate control scheme to control load on the shared channel by adjusting sending rate according to the estimated channel state and the amount of AF traffic. We further propose a RTS retry limit adaptation scheme for loss rate differentiation at the link layer. Through extensive simulations, we show that proposed schemes are effective to differentiate forwarding assurance in multi-hop wireless networks.

Compact optical CDMA passive optical network with differentiated services

In this paper the improved versions of quadratic congruence (QC) codes for cardinality enlargement are proposed for spectral-amplitude coding (SAC) optical code-division multiple-access (OCDMA) network. These codes can adopt two-code keying for performance enhancement and the interference can be eliminated in the decoder by our interference elimination scheme proposed previously. In addition, to mitigate the cardinality reduction in the two-code keying scheme, hybrid schemes using QC and/or stuffed QC (SQC) codes for differentiated service provision are proposed. These two code families are capable of using compact encoders and decoders for the application of passive optical networks.

Extended EDCA for delay guarantees in wireless local area networks

Despite their very broad diffusion, IEEE 802.11 Wireless Local Area Networks (WLANs) are not able to provide service differentiation and to support real-time multimedia applications, due to their channel access methods. To overcome these limitations, the 802.11e working group has proposed the Enhanced Distributed Coordination Access (EDCA) scheme, which achieves service differentiation on a statistical basis by properly mapping user Quality of Service (QoS) requirements to channel contention parameters. Such a scheme will be included in the emerging 802.11n standard and in the revision of the 802.11 standard. However, it has been widely demonstrated that, especially at high network loads, EDCA does not provide an effective usage of the channel capacity. In particular, it is unable to provide a bounded delay service to all kinds of multimedia flow because flows with lower channel access priorities are starved to advantage only those with the highest priority. To fix this undesired behavior and improve wireless LAN performance, this paper proposes a new Extended EDCA (E 2DCA) scheme, that is compliant with 802.11e specifications. By exploiting a closed-loop control algorithm, E 2DCA performs a distributed dynamic bandwidth allocation, providing guarantees on average/absolute delays to real-time media flows, regardless of their priorities. Moreover, an innovative Call Admission Control (CAC) procedure has been developed. Using the ns-2 simulator, the effectiveness of the algorithm has been investigated in realistic network scenarios, involving a mix of audio, video, and FTP flows, at several network loads and with random losses. Results have shown that the proposed scheme is able to provide a bounded delay service to multimedia flows in a wide range of network loads and frame loss ratios.

Throughput Analytical Model and Adaptive MAC Scheme for IEEE 802.11e EDCA Based on AIFS Differentiation

针对IEEE 802.11e EDCA(enhanced distributed channel access)支持业务区分服务的特点,提出了一个基于AIFS(arbitration inter-frame space)区分的信道吞吐率分析模型,该模型将不同接入等级的业务统一到一个信道模型中进行分析.通过数值计算结果与仿真实验结果的对比,验证了该模型的准确性,尤其是在分析信道吞吐率方面更优于Xiao 的Markov 链模型.根据提出的分析模型,研究了近似优化条件,使得各类优先级业务的发送概率平衡虚拟发 送时间段中空闲时间与冲突持续时间对系统性能的影响,实现靠近最优的信道吞吐率,从而使计算复杂度大为减小. 利用数值分析的方法验证了近似优化条件实现靠近最优信道吞吐率的可行性.最后,提出的DPS(dynamicparameter-tuning scheme)算法根据负载情况自适应地调整不同级别业务的相应参数,使得系统时时满足优化条件,在各种场景下都能实现最大信道吞吐率,同时又满足EDCA 支持QoS 区分的要求.仿真结果验证了DPS 算法不仅能够根据竞争节点的数目变化对信道吞吐率进行优化,而且其性能也明显优于标准的IEEE 802.11e EDCA 机制.;This paper proposes an AIFS-based multi-class model to study the saturation channel throughput on the basis of the operation mechanism of IEEE 802.11e EDCA (enhanced distributed channel access) supporting servicedifferentiation. The proposed model is calculated numerically and validated against simulation results, a good matchbetween the analytical model and simulation is observed. In particular, this paper compares the proposed modelwith Xiao’s Markov chain model under the same configures. Based on the proposed model, this paper researches thequasi-optimal condition to avoid the computational complexity but still maintain the channel throughput close to itsoptimal value. Finally, the paper proposes an adaptive p-persistent MAC scheme, named DPS (dynamicparameter-tuning scheme), to assign appropriate different transmission probabilities (or contention window size) of different classes. Through DPS, it is feasible to provide service differentiation and achieve targeted throughput ratioamong different classes, at the same time to maximize the total channel throughput. Simulation and numericalresults show that DPS can effectively achieve the performance goal under a variety of network conditions, and achieve higher channel throughput than standard IEEE 802.11e EDCA in all different environments.

A simple adaptive optimization scheme forIEEE 802.11 with differentiated channel access

This letter proposes an adaptive scheme to optimize the system throughput of IEEE 802.11 with differentiated channel access ability. Due to the difficulty of estimating the number of active stations and that approaches based on the estimation may not converge reported in previous research, the proposed scheme is developed to maximize the system throughput without the requirement of station number information while providing service differentiation among different traffic classes. Specially, the scheme is simple to implement and it only requires to measure the time the channel is in idle and collision states separately. Performance evaluation results show that the scheme is effective in achieving near to the theoretical maximum system throughput.

A new protocol for security and QoS in IP networks

To effectively manage network resources and to serve different traffic needs, several studies have been done in the Quality of Service (QoS) area. Basically, 'Multi-Field' (MF) packet classifiers classify a packet by looking for multiple fields of the IP-TCP headers, recognise which flow the packet belongs to, and according to this information, provide service differentiation in IP networks. However, for security purposes, existing security protocols (such as the IPSec ESP) hide much of this information in their encrypted payloads, preventing network control devices such as routers and switches from utilising this information in performing classification appropriately. The ESPQ protocol deals with this problem but it has some security weaknesses. In this paper, we present the ESPQ vulnerabilities and we propose QoS-friendly Encapsulated Security Payload (Q-ESP) as a security protocol that provides both security and QoS support.

A QoS Control Mechanism to Provide Service Differentiation and Overload Protection to Internet Scalable Servers

Nowadays, enterprises providing services through Internet often require online services supplied by other enterprises. This entails the cooperation of enterprise servers using Web services technology. The service exchange between enterprises must be carried out with a determined level of quality, which is usually established in a service level agreement (SLA). However, the fulfilment of SLAs is not an easy task and requires equipping the servers with special control mechanisms which control the quality of the services supplied. The first contribution of this research work is the analysis and definition of the main requirements that these control mechanisms must fulfil. The second contribution is the design of a control mechanism which fulfils these requirements and overcomes numerous deficiencies posed by previous mechanisms. The designed mechanism provides differentiation between distinct categories of service consumers as well as protection against server overloads. Furthermore, it scales in a cluster and does not require any modification to the system software of the host server, or to its application logic.