An integrated congestion control mechanism for optimized performance using two-step rate controller in optical burst switching networks

Optical burst switching (OBS) is a promising solution to implement the optical internet backbone. However, the lack of adequate congestion-control mechanisms may result in high burst loss. Schemes such as fiber delay line (FDL), wavelength conversion, and deflection routing to reduce burst collision are unable to prevent the network congestion effectively. To address this problem, we propose and investigate a global solution, called Integrated Congestion-Control Mechanism (ICCM), for OBS networks. ICCM, which combines congestion avoidance with recovery mechanism, restricts the amount of burst flows entering the network according to the feedback information from core routers to edge routers to prevent network congestion. Also, a flow-policing scheme is proposed to intentionally drop the overloaded traffic with a certain probability at a core router to support fairness among flows. Moreover, the transmission rate of each flow is controlled to achieve optimized performance such as maximizing throughput or minimizing loss probability using two-step rate controller at the edge router. Simulation results show that ICCM effectively eliminates congestion within the network and that, when combined with a flow-policing mechanism, the fairness for competing flows can be supported while maintaining effective network performance.     

面向无线传感器网络不同业务的区分服务算法

针对无线传感器网络中不同等级业务在传输过程中对QoS的不同要求,提出了一种适合无线传感器网络中不同业务的区分服务算法——EMHNS算法。该算法根据不同等级的业务来选择合适的转发节点,从而保证实时业务传输的时延能够达到最小,而尽力而为业务传输时时延不是考虑的主要因素,在传输尽力而为业务的时候重点考虑网络能耗均衡。仿真结果表明,与定向扩散协议相比,该算法能降低实时业务的端对端延时,并使网络生存期得到提高。     

Multi-hop cellular networks: Architecture and protocols for best-effort and real-time communication

Until recently, research on cellular networks concentrated only in single-hop cellular networks. The demand for high throughput has driven to architectures that use multiple hops in the presence of infrastructure. We propose an architecture for multihop cellular networks (MCNs). MCNs combine the benefits of having a fixed infrastructure of base stations and the flexibility of Ad hoc networks. They are capable of achieving much higher throughput than current cellular systems, which can be classified as single-hop cellular networks (SCNs). In this work, we propose an extended architecture for MCN using the IEEE 802.11 standard for wireless LANs for connection-less service and a TDMA-based solution for real-time support. We provide a general overview of the architecture and the issues involved in the design of MCNs, in particular the challenges to be met in the design of a routing protocol, a channel assignment scheme, and a mobility management scheme. We also propose a routing protocol called Base-Assisted Ad hoc Routing (BAAR) protocol for use in such networks and a model for the performance analysis of MCNs and SCNs. We also conduct extensive experimental studies on the performance of MCNs and SCNs under various load (TCP, UDP, and real-time sessions) and mobility conditions. These studies clearly indicate that MCNs with the proposed architecture and routing protocol are viable alternatives for SCNs, in fact they provide much higher throughput. MCNs are very attractive for best-effort packet radio where they can achieve an increase in throughput up to four when compared to similar SCNs. But for real-time traffic, even though they do outperform SCNs, they also suffer from a few disadvantages such as frequent hand-offs and throughput degradation at high mobility. We also present results from a detailed comparison study of our architecture for MCN with the Hybrid Wireless Network (HWN) architecture and Integrated Cellular Ad hoc Relaying (iCAR) Architecture.     

Hard real-time communication in multiple-access networks

With the increasing use of distributed hard real-time systems, the ability of computer networks to handle hard real-time message traffic is becoming more important. For traditional networks, maximizing the throughput or minimizing the average message delay is the most important performance criteria. In the hard real-time domain, however, concern focuses on satisfying the time constraints of individual messages. This paper examines recent developments in hard real-time communication in local area multiple-access networks. Two general strategies are used in hard real-time communication: the guarantee strategy and the best-effort strategy. In the former, messages are guaranteed to meet their deadlines during normal operation of the network. In the best-effort strategy, the network will attempt to send messages before their deadlines, but no guarantees are given. Real-time message traffic can be distinguished according to whether it is best suited for the guarantee strategy or the best-effort strategy. Although this paper concentrates on multiple-access networks, many of the concepts presented and lessons learned are also applicable to other types of networks.     

Ad Hoc网络中SWAN模型改进及其仿真研究

SWAN是AdHoc网络中的一种无状态网络协议,利用分布式控制算法来传递分类服务。这种QoS模型把数据业务分为两类进行不同处理,即对尽力而为的UDP和TCP业务采用速率控制的策略而对实时的UDP业务采用基于源节点的接纳控制策略。然而现有模型在路由模块采用普通的路由协议,导致了路由和对整个路径资源探测两个过程分离开来;在接纳控制模块仅仅区分了节点间的业务而没有区分相同节点间的不同业务。该文针对这一问题对现有模型的修改主要体现在两个方面:(1)在路由模块用QoS路由替换了原有普通路由协议,路由和整个路径资源探测由QoS路由完成,从而减少了实时业务等待发送时间;(2)针对SWAN首次提出了基于数据流的服务,并且在接纳控制模块进行了相应修改。最后的仿真中表明了该文的修改是有效的,提高了模型的性能。     

A hop-by-hop flow controller for a virtual path

In this paper, we propose a hop-by-hop robust controller for the flow regulation of the best-effort (ABR) traffic along a virtual path (VP) in high-speed networks. The local controller at each VP switch can regulate the transmission rate of virtual connections (VCs) based on the knowledge of the buffer occupancy in downstream VP switches. The fluid-flow model is used to design the hop-by-hop congestion controller, and used to study dynamic and steady behaviors of the network. A condition for the network's stability is derived. It is shown that with this controller applied, the network is asymptotically stable without oscillation. It is also shown that the proposed controller can achieve fairness and high utilization, and reduce the overhead traffic.     

Voice and video transmissions with global data parameter control for the IEEE 802.11e enhance distributed channel access

Best-effort data control and admission control are vital to guarantee quality of service for real-time (voice and video) transmissions in the IEEE 802.11e wireless LANs. In this paper, we propose and study a global data parameter control scheme integrated with a measurement-based admission control scheme for the IEEE 802.11e enhanced distributed channel access. In the proposed global data control scheme, the access point dynamically controls best-effort data parameters of stations globally based on traffic condition. Such a global/centralized data parameter control mechanism provides the best fairness for data transmissions among stations. In the proposed centrally-assisted distributed admission control scheme for voice and video transmissions, stations listen to available budgets from the access point to make decisions on acceptance or rejection of a voice or video stream. Such a scheme provides good differentiation among different access categories and provides good fairness among real-time streams within the same access category. The proposed mechanisms are evaluated via extensive simulations. Studies show that, with the proposed global data control scheme and the admission control scheme, quality of service can be greatly improved while maintaining a good utilization.     

Structuring communication software for quality-of-serviceguarantees

We propose architectural mechanisms for structuring host communication software to provide QoS guarantees. We present and evaluate a QoS sensitive communication subsystem architecture for end hosts that provides real time communication support for generic network hardware. This architecture provides services for managing communication resources for guaranteed QoS (real time) connections, such as admission control, traffic enforcement, buffer management, and CPU and link scheduling. The architecture design is based on three key goals: maintenance of QoS guarantees on a per connection basis, overload protection between established connections, and fairness in delivered performance to best effort traffic. Using this architecture we implement real time channels, a paradigm for real time communication services in packet switched networks. The proposed architecture features a process per channel model that associates a channel handler with each established channel. The model employed for handler execution is one of “cooperative” preemption, where an executing handler yields the CPU to a waiting higher priority handler at well defined preemption points. The architecture provides several configurable policies for protocol processing and overload protection. We present extensions to the admission control procedure for real time channels to account for cooperative preemption and overlap between protocol processing and link transmission at a sending host. We evaluate the implementation to demonstrate the efficacy with which the architecture maintains QoS guarantees on outgoing traffic while adhering to the stated design goals     

Topology-aware wavelength partitioning for DWDM OBS networks: A novel approach for absolute QoS provisioning

Optical Burst Switching (OBS) is a promising switching technology for the next generation all-optical networks. An OBS network without wavelength converters and fiber delay lines can be implemented simply and cost-effectively using the existing technology. However, this kind of networks suffers from a relatively high burst loss probability at the OBS core nodes. To overcome this issue and consolidate OBS networks with QoS provisioning capabilities, we propose a wavelength partitioning approach, called Optimization-based Topology-aware Wavelength Partitioning approach (OTWP). OTWP formulates the wavelength partitioning problem, based on the topology of the network, as an Integer Linear Programming (ILP) model and uses a tabu search algorithm (TS) to resolve large instances efficiently. We use OTWP to develop an absolute QoS differentiation scheme, called Absolute Fair Quality of service Differentiation scheme (AFQD). AFQD is the first absolute QoS provisioning scheme that guarantees loss-free transmission for high priority traffic, inside the OBS network, regardless of its topology. Also, we use OTWP to develop a wavelength assignment scheme, called Best Effort Traffic Wavelength Assignment scheme (BETWA). BETWA aims to reduce loss probability for best effort traffic. To make AFQD adaptive to non-uniform traffic, we develop a wavelength borrowing protocol, called Wavelength Borrowing Protocol (WBP). Numerical results show the effectiveness of the proposed tabu search algorithm to resolve large instances of the partitioning problem. Also, simulation results, using ns-2, show that: (a) AFQD provides an excellent quality of service differentiation; (b) BETWA substantially decreases the loss probability of best effort traffic to a remarkably low level for the OBS network under study; and (c) WBP makes AFQD adaptive to non-uniform traffic by reducing efficiently blocking probability for high priority traffic.     

Power-aware opportunistic downlink scheduling in IEEE 802.16 wireless networks

The IEEE 802.16 is a standard for fixed and mobile Broadband Wireless Access (BWA). In this paper, we deal with two key challenges of 802.16-based networks. First, terminals close to cell edge experience poor channel quality, due to severe path-loss and high interference from concurrent transmissions in nearby cells. To address this issue, we propose a framework based on a static partitioning of bandwidth into chunks with different transmission power levels. Terminals with impaired channel conditions can then benefit from being allocated a higher amount of transmission power than the others. Secondly, transmissions should be scheduled according to Quality of Service (QoS) requirements to keep users with real-time video or voice calls satisfied, while best-effort connections should fairly share the remaining capacity. To this aim, we propose a scheduling algorithm, called Power-aware Opportunistic Downlink Scheduling (PODS), that aims at meeting both the QoS and fairness requirements, while taking into account the different power levels of the bandwidth chunks. The performance of the proposed scheduler is assessed through detailed packet-level simulation in realistic scenarios and compared with well-known scheduling algorithms. Results confirm that PODS is able to exploit power boosting to provide real-time connections with the desired level of QoS, irrespectively of their MSs’ channel quality.     

一种支持比例区分服务的OBS数据信道调度算法

光突发交换（OBS）是实现IP／DWDM网络的一种极有前途的方案,该文提出了一种用于OBS网络的PDF数据信道调度算法,此算法能支持比例区分服务，保证高优先级业务数据比低优先级业务数据得到更可靠的传输．计算机仿真验证了PDF调度算法的性能．     

An adaptive redundancy control method for erasure-code-basedreal-time data transmission over the Internet

We propose an adaptive redundancy control method for erasure-code-based real-time data transmission over the Internet. The loss rate is an important quality of service (QoS) parameter for real-time data transmission. However, real-time data transmission over best-effort networks, such as the Internet, suffers from a frequent packet loss due to traffic congestion. Erasure-code-based loss recovery scheme is widely used for loss recovery on the Internet. We propose a redundancy estimation algorithm which considers consecutive losses since the loss recovery rate depends on the amount of redundancy data. A continuous time Markov chain is used for modeling the loss process and adjusting the number of redundant packets. Measurements and simulation results show that the proposed scheme can be used as an efficient loss recovery algorithm for real-time data transmission over the Internet     

基于区分服务的无线多媒体传感器网络QoS路由协议*

针对无线多媒体传感器网络数据量大且不同业务传输的QoS约束不同的特点,提出了一种数据融合的区分服务的QoS路由算法（DF-DSQR）。该算法在兴趣泛洪期间建立实时（RT）和尽力而为（BE）业务两类梯度,采用优先级排队模型对两类业务的传输进行分级处理,并采用数据融合转发机制,为RT业务和BE业务提供了保证QoS的路由路径。仿真结果表明,该算法既能保证实时业务低时延的要求,又能保证尽力而为业务的QoS要求,均衡了网络能耗,延长了网络生存期。     

MediaWorm: a QoS capable router architecture for clusters

With the increasing use of clusters in real-time applications, it has become essential to design high-performance networks with quality-of-service (QoS) guarantees. We explore the feasibility of providing QoS in wormhole switched routers, which are widely used in designing scalable, high-performance cluster interconnects. In particular, we are interested in supporting multimedia video streams with CBR and VBR traffic, in addition to the conventional best-effort traffic. The proposed MediaWorm router uses a rate-based bandwidth allocation mechanism, called Fine-Grained VirtualClock (FGVC), to schedule network resources for different traffic classes. Our simulation results on an 8-port router indicate that it is possible to provide jitter-free delivery to VBR/CBR traffic up to an input load of 70-80 percent of link bandwidth and the presence of best-effort traffic has no adverse effect on real-time traffic. Although the MediaWorm router shows a slightly lower performance than a pipelined circuit switched (PCS) router, commercial success of wormhole switching, coupled with simpler and cheaper design, makes it an attractive alternative. Simulation of a (2/spl times/2) fat-mesh using this router shows performance comparable to that of a single switch and suggests that clusters designed with appropriate bandwidth balance between links can provide required performance for different types of traffic.     

Ad Hoc网络中SWAN模型的改进研究

SWAN模型应用于Ad Hoc网络后,通过NS2仿真表明网络实时业务的分组递交率、业务吞吐量等性能可提高15%左右,平均端到端时延减少90%,但网络非实时业务的性能除业务吞吐量有较大幅度的提高,分组递交率和时延性能均有所下降,为此提出了一种增强的尢状态无线自组网速率控制方案:ESWAN.仿真表明ESWAN较SWAN而言不仪可以提高网络实时业务性能,而且网络非实时业务分组递交率可提高5%,时延减少38%.     

Traffic scheduling solutions with QoS support for an input-buffered multimedia router

Quality of service (QoS) support in local and cluster area environments has become an issue of great interest in recent years. Most current high-performance interconnection solutions for these environments have been designed to enhance conventional best-effort traffic performance, but are not well-suited to the special requirements of the new multimedia applications. The multimedia router (MMR) aims at offering hardware-based QoS support within a compact interconnection component. One of the key elements in the MMR architecture is the algorithms used in traffic scheduling. These algorithms are responsible for the order in which information is forwarded through the internal switch. Thus, they are closely related to the QoS-provisioning mechanisms. In this paper, several traffic scheduling algorithms developed for the MMR architecture are described. Their general organization is motivated by chances for parallelization and pipelining, while providing the necessary support both to multimedia flows and to best-effort traffic. Performance evaluation results show that the QoS requirements of different connections are met, in spite of the presence of best-effort traffic, while achieving high link utilizations.     

一种基于IEEE 802.11e的多跳无线网络拥塞控制协议

多跳无线网络中网络拥塞的出现将严重降低网络的性能。基于802.11e提供的区分业务类型的信道接入优先级机制,提出了一种对尽力而为(best-effort)类型业务动态调整其优先级进行网络拥塞控制的协议。该算法的主要思想是对发生网络拥塞的节点提升其业务流传输的优先级使其获得更多的传输机会以缓解拥塞状况,并对严重的网络拥塞状况采取反向施压的策略降低上游节点业务流的转发速率。仿真结果表明,该算法有效地提高了网络重负载情况下的吞吐量。     

一种IEEE 802.16宽带无线接入系统的QoS架构

IEEE 802.16 MAC协议虽然对各类业务的QoS提供支持,却没有定义完整的QoS保证机制.本文通过分析IEEE 802.16现有的QoS架构,提出了一种具体的QoS架构,并对相应的调度算法进行了分析.仿真结果表明,该架构能够对实时业务提供较好的支持,同时维持其它业务的带宽在可接受的范围之内.     

A new fast friendly window-based congestion control for real-time streaming media transmission

1 Introduction In the current Internet, not all applications use TCP and they do not follow the same concept of fairly sharing the available bandwidth. The rapid growing of real-time streaming media applications will bring much UDP traffic without integrating TCP compatible congestion control mechanism into Internet. It threats the quality of service (QoS) of real-time applications and the stability of the current Internet. For this reason, it is desirable to define appropriate rate rule…     

Differentiation, QoS guarantee, and optimization for real-time traffic over one-hop ad hoc networks

Nodes having a self-centrically broadcasting nature of communication form a wireless ad hoc network. Many issues are involved to provide quality of service (QoS) for ad hoc networks, including routing, medium access, resource reservation, mobility management, etc. Previous work mostly focuses on QoS routing with an assumption that the medium access control (MAC) layer can support QoS very well. However, contention-based MAC protocols are adopted in most ad hoc networks since there is no centralized control. QoS support in contention-based MAC layer is a very challenging issue. Carefully designed distributed medium access techniques must be used as foundations for most ad hoc networks. In this paper, we study and enhance distributed medium access techniques for real-time transmissions in the IEEE 802.11 single-hop ad hoc wireless networks. In the IEEE 802.11 MAC, error control adopts positive acknowledgement and retransmission to improve transmission reliability in the wireless medium (WM). However, for real-time multimedia traffic with sensitive delay requirements, retransmitted frames may be too late to be useful due to the fact that the delay of competing the WM is unpredictable. In this paper, we address several MAC issues and QoS issues for delay-sensitive real-time traffic. First, a priority scheme is proposed to differentiate the delay sensitive real-time traffic from the best-effort traffic. In the proposed priority scheme, retransmission is not used for the real-time traffic, and a smaller backoff window size is adopted. Second, we propose several schemes to guarantee QoS requirements. The first scheme is to guarantee frame-dropping probability for the real-time traffic. The second scheme is to guarantee throughput and delay. The last scheme is to guarantee throughput, delay, and frame-dropping probability simultaneously. Finally, we propose adaptive window backoff schemes to optimize throughput with and without QoS constraints.