一种基于延时PDF测量的连接接纳控制算法

相比与基于模型的连接接纳控制(CAC)算法,基于测量的CAC(MBCAC)算法能够大大提高了网络资源的利用率。准确的网络状态信息对于提高MBCAC的性能至关重要。本文提出了一种基于延时概率密度函数测量的CAC算法,它采用了两种机制有效提高了网络状态测量的准确性。一是测量网络中每个路由器出口的延时概率密度函数,二是通过混合更新方法及时更新网络状态。仿真结果表明它在保证业务服务质量要求的前提下能有效提高网络状态测量的准确性,具有较低的业务流拒绝率和较高的链路利用率。     

一种基于延时PDF测量的连接接纳控制算法

相比与基于模型的连接接纳控制(CAC)算法,基于测量的CAC (MBCAC)算法能够大大提高了网络资源的利用率.准确的网络状态信息时于提高MBCAC的性能至关重要.本文提出了一种基于延时概率密度函数测量的CAC算法,它采用了两种机制有效提高了网络状态测量的准确性.一是测量网络中每个路由器出口的延时概率密度函数,二是通过混合更新方法及时更新网络状态.仿真结果表明它在保证业务服务质量要求的前提下能有效提高网络状态测量的准确性,具有较低的业务流拒绝率和较高的链路利用率.     

Heavy业务流的有效带宽及其基于测量的接纳控制算法

基于具突发性Heavy业务流的TES(Transform Expand Sample)模型,推导出一个计算Heavy业务流有效带宽的实用的公式,并由此公式求得的有效带宽,作为基于测量的接纳控制(MBAC)算法中新业务流所申请的带宽。仿真结果表明,采用该计算公式求得的有效带宽,MBAC算法可以取得更好的网络性能。     

WLAN中基于混合模式的接纳控制算法

针对WLAN标准IEEE 802.11e中 EDCA不能提供定量的服务质量(QoS)的问题,提出了一种混合模式(基于模型和测量)的接纳控制算法。通过建立退避实例的各个状态转移的Markov模型,利用贝塞尔削减规则得出网络性能指标的解析表达式,并根据测量的信道的实时状况预测新业务流可获得的吞吐量,最后提出了一种基于吞吐量的接纳控制算法。实验结果表明,该算法保证了已经接入业务流的服务质量,同时接纳了更多的新业务流,提高了网络的吞吐量。     

区分服务网络基于测量的接纳控制方案的设计与应用

提出了一种分布式可扩展的接纳控制方案，其目的是为区分服务网络提供端到端服务质量（Quality of Services,QoS)保证，该方案主要由以下部分构成：（1）连接接纳控制协议，主要负责主机和网络节点以及网络节点和带宽代理之间的信息传送，实现对连接请求的串行操作；（2）位于网络核心节点的可用带宽估计算法；（3）位于网络边缘节点的接纳控制算法；给出了该方案在视频传输方面的应用实例；利用多种网络拓扑结构和QoS指标评价该方案的性能，实验结果表明该方案能准确地控制可接纳区域和提高网络资源的利用率。     

IPv6网络中基于优先级的可用带宽测量方法

利用IPv6报文头部的流标签字段和业务流类别字段，通过增设专门用于网络测量的“测试级”，提出了一种IPv6网络中的端到端可用带宽测量方法——Hurnble-Burst．该方法对网络中已有的业务流不产生任何影响，并且测量时间非常短．与现有网络中可用带宽测量方法相比，该方法可以真正被实际应用程序所采用，可以应用在无线网络等低带宽的网络环境，而且也适用于多媒体QoS动态调节等实时场景．实验表明，该方法简单、有效、快速，并对网络本身无影响．     

基于IEEE 802.16的接纳控制机制

分析IEEE 802.16的QoS机制,针对其没有详细规定接纳控制算法的情况,结合协议中定义的业务类型QoS特性,在信令交互机制下,提出一种基于优先级的动态带宽分配接纳控制机制。仿真结果表明,与预留带宽的固定带宽分配机制相比,采用该机制后,系统的切换连接掉线率、新增连接的阻塞率和带宽利用率得到改善。     

基于跨层的自适应预留带宽和多重QoS保证的EDCA流接纳控制

提出了基于跨层的自适应带宽预留和多重QoS保证的802.11eEDCA分布式流接纳控制。首先自适应分配各站点OFDM子载波比特以最大化信道容量,并将比特率跨层传送到MAC层。基于此,提出了基于分布式测量的动态带宽预留机制,使预留带宽自适应各用户信道特点和业务特征;提出了半模式化的中心控制的剩余因子估计方法,从而克服了直接测量的不准确性和分布式估计的局部性,并降低了计算复杂度;提出了基于协议模型的带宽和碰撞率双重接纳标准,使多重QoS参数同时得到保证。通过这些措施得到自上至下的自适应接纳控制。仿真表明,提出的接纳控制机制能较大地提高资源利用率,更好地保证业务质量。     

一种基于测量的动态公平接纳控制算法

接纳控制算法是接纳控制的核心,在基于参数和基于测量的这两类接纳控制算法中,基于测量的接纳控制无需知道应用的流量模型,其次它能动态适应网络的负载变化,提高网络资源的利用率;然而最新的研究表明,仅仅追求高接纳率的接纳控制算法会造成对不同带宽QoS需求的连接的接纳非公平性,并且历经多跳的流更不易被接纳;文章的目的是解决基于测量的接纳控制算法的非公平性问题,文中分析了基于测量的接纳控制的基本思想和非公平性产生的原因,并在此基础上提出和实现了一种基于测量的HR接纳控制算法;仿真结果表明,该算法在以降低很小的接纳率的代价下,能有效地克服基于测量类接纳控制算法的非公平性问题。     

基于测量的QoS参数估计及其应用

提出了一种基于测量的QoS参数估计方法,该方法使得用户无须事先为业务源建立相应的业务模型并向网络提交其业务模型参数,而是通过对业务流的统计特性进行实时测量来动态估计相应的QoS参数,从而克服了基于模型QoS参数估计方法所固有的缺陷,便于网络进行连接允许控制和带宽的动态分配.     

Impact of bandwidth request schemes for Best-Effort traffic in IEEE 802.16 networks

In IEEE 802.16 networks, bandwidth request–grant schemes are employed for reducing data collision and supporting various QoS requirements. In this paper, we investigate the impact of such schemes on Best-Effort (BE) traffic. We examine three candidate schemes. In the first scheme, each Subscribe Station (SS) attempts to request bandwidth in every frame to reduce delay. In the second scheme, the number of bandwidth request is limited to avoid collisions in bandwidth request. In the third scheme, a base station allocates bandwidth to each SS based on the measured sending rate without explicit bandwidth request. We quantitatively analyze the performance of these schemes in terms of the collision rate and buffer length. We also present a simulation study to validate our analysis and to observe the impact of these schemes on BE traffic. This paper shows that IEEE 802.16 networks can be effectively managed through appropriate bandwidth request schemes. It is also shown that bandwidth allocation without request can be an alternative for increasing utilization.     

RED-VBR: a renegotiation-based approach to support delay-sensitive VBR video

Previous approaches to supporting video on packet-switched networks include deterministic service, statistical service, predicted service, and feedback-based schemes. These schemes represent different tradeoffs in quality of service (QOS), achievable network utilization, and method of dealing with overload. In this paper, we propose a new service called REnegotiated Deterministic Variable Bit Rate Service (RED-VBR) that attempts to strike an efficient balance with the above tradeoffs. The approach is based on deterministic guarantees with client-controlled renegotiation of traffic and QOS parameters and graceful adaptation during overload periods. We introduce a connection admission control algorithm for RED-VBR which bounds the renegotiation failure probability. We evaluate the scheme using two traces of MPEG-compressed video and show that, even with simple renegotiation polices and relatively low renegotiation frequencies, high network utilization in the range of 50–80% can be achieved. For traffic that is bursty over long intervals, this represents a 100–150% improvement in network utilization compared to deterministic service. Compared to statistical and predicted service, our approach allows more graceful and client-controlled QOS degradation during overload periods.     

自适应调整TCP阻塞控制窗口算法研究

提出了新的TCP速率调整算法.根据边缘路由器缓冲区中的输入数据报和输出数据报的变化,得到合理阻塞控制窗口,直接通过明确阻塞标记数据报返回到发送终端,从而改变了TCP发送速率.通过对仿真结果的分析,新算法可以明显地控制TCP的业务量,限制边缘路由器的队列的拥塞,大大降低数据报的丢失率,从而提高TCP的延迟性能和带宽分配的公平性.     

Availability guarantee in survivable WDM mesh networks: A time perspective

Since availability is an important quality-of-service (QoS) factor in mesh networks, different service provision with availability guarantee have been discussed by many researchers in the literature. However, with the increasing demand for mesh networks to support both data and real-time multimedia traffic, multiple availability requirements may be made during one connection’s holding time. The traffic of different availability requirements has to be routed by special wavelengths. In this paper we discuss availability guarantee in mesh networks from the perspective of time and propose a new scheme called Time Aware Availability Guarantee (TAAG). The routing paths of each connection are adjusted according to the different availability requirements in different time spans. Simulation results show that the proposed scheme outperforms the previous schemes such as Time Unaware Availability Guarantee (TUAG) in terms of resource utilization, blocking probability and traffic throughput.     

Detecting superpoints through a reversible counting Bloom filter

Internet attacks such as distributed denial-of-service (DDoS) attacks and worm attacks are increasing in severity. Identifying realtime attack detection and mitigation of Internet traffic is an important and challenging problem. For example, a compromised host doing fast scanning for worm propagation often makes an unusually high number of connections to distinct destinations within a short time. We call such a host a superpoint, which are sources that connect to a large number of distinct destinations. Detecting superpoints is very important in developing effective and efficient traffic engineering schemes. We propose two novel schemes for detecting superpoints and prove guarantees on their accuracy and memory requirements. These schemes are implemented by introducing a reversible counting Bloom filter (RCBF), a special counting Bloom filter. The RCBF consists of 4 hash functions which projectively select some consecutive bits from original strings as function values. We obtain the information of superpoints using the overlapping of hash bit strings of the RCBF. The theoretical analysis and experiment results show that our schemes can precisely and efficiently detect superpoints.     

Link-level traffic scheduling for providing predictive QoS in wireless multimedia networks

A set of centralized burst-level cell scheduling schemes, namely, First Come First Served with Frame Reservation (FCFS-FR), FCFR-FR+, Earliest Deadline First with Frame Reservation (EDF-FR), EDF-FR+, and Multitraffic Dynamic Reservation (MTDR), are investigated for transmission of multiservice traffic over time division multiple access (TDMA)/time division duplex (TDD) channels in wireless ATM (WATM) networks. In these schemes, the number of time slots allocated to a virtual circuit (VC) during a frame-time is changed dynamically depending on the traffic type, system traffic load, the time of arrival (TOA)/time of expiry (TOE) value of the data burst and data burst length. The performances of these schemes are evaluated by computer simulation for realistic voice, video and data traffic models and their quality-of-service (QoS) requirements in a wireless mobile multimedia network. Both the error-free and the correlated fading channel conditions are considered. Simulation results show that the EDF-FR+ and MTDR schemes outperform the other schemes and can provide high channel utilization with predictive QoS guarantee in a multiservice traffic environment even in the presence of bursty channel errors. The EDF-FR+ scheme is found to provide better cell multiplexing performance than the MTDR scheme, Such a scheme would be easy to implement and would also result in a power conservative TDMA/TDD medium access control (MAC) protocol for broadband wireless access. Burst-level cell scheduling schemes such as EDF-FR+ can be easily adapted as MAC protocols in the emerging differentiated services (DS) enhanced wireless Internet protocol (IP) networks.     

A priority media access control protocol for video communication support on CSMA/CD LANs

Real-time multimedia communication applications demand performance requirements which differ significantly from conventional data communication applications. Current local area networks (LANs) provide efficient transport for bursty data traffic; however, they cannot necessarily provide quality of service guarantees for real-time communications. In this work we introduce and investigate an experimental priority protocol for supporting real-time communication on Ethernet, a popular implementation of multiple-access broadcast bus LANs. We examine the new protocol, known as Priority Mode-CSMA/CD (PM-CSMA/CD), providing a high priority (HP) class with CSMA/CD employed for standard priority (SP) traffic. PM-CSMA/CD performance is examined through computer simulation of videotelephony workstations operating over the shared bus LAN. Over all observed traffic conditions, the priority protocol provides performance satisfying real-time packet transport requirements of audio and video streams. The primary advantage of our protocol over similar priority schemes is its physical layer compatibility with standard CSMA/CD. The protocol also provides improved channel utilization with increasing high priority load, with no penalty in SP class performance at low to medium network loads.     

Evaluating the energy consumption and the silicon area of on-chip interconnect architectures

Sophisticated on-chip interconnects using packet and circuit switching techniques were recently proposed as a solution to non-scalable shared-bus schemes currently used in Systems-on-Chip (SoCs) implementation. Different interconnect architectures have been studied and adapted for SoCs to achieve high throughput, low latency and energy consumption, and efficient silicon area. Recently, a new on-chip interconnect architecture by adapting the WK-recursive network topology structure has been introduced for SoCs. This paper analyses and compares the energy consumption and the area requirements of Wk-recursive network with five common on-chip interconnects, 2D Mesh, Ring, Spidergon, Fat-Tree and Butterfly Fat-Tree. We investigated the effects of load and traffic models and the obtained results show that the traffic models and load that ends processing elements has a direct effect on the energy consumption and area requirements. In these results, WK-recursive interconnect generally has a higher energy consumption and silicon area requirements in heavy traffic load.     

A simple recursive scheme for adjusting the contention window size in IEEE 802.11e wireless ad hoc networks

The IEEE 802.11e standard has been introduced recently for providing Quality of Service (QoS) capabilities in the emerging wireless local area networks. This standard introduces a contention window based Enhanced Distributed Channel Access (EDCA) technique that provides a prioritized traffic to guarantee the minimum bandwidth needed for time critical applications. However, the EDCA technique resets the Contention Window (CW) of the mobile station statically after each successful transmission. This static behavior does not adapt to the network state since it reduces the network usage and results in bad performance and poor link utilization whenever the demand for link utilization increases. This paper proposes a new adaptive differentiation technique for IEEE 802.11e Wireless Local Area Networks that takes into account the network state before resetting the contention window. In the new technique, the congestion level of the network is sensed by using previous CW values. Three other enhancement techniques that focus on network adaptation are also discussed. Their main limitations are the high complexity of the implemented algorithms and their slow adaptation to the network state when the channel experiences bursty traffic. The proposed technique is compared to the original differentiation techniques of IEEE 802.11a and IEEE 802.11e standards, as well as to the enhancement schemes. Results show that the proposed adaptive technique outperforms IEEE 802.11e and is comparable to the other enhancement schemes while maintaining relatively low complexity requirements.