基于逆向传输机制的反馈型两级交换结构

为解决FTSA-2-SS结构中的信元冲突、信元失序以及交换流程复杂化等问题,该文提出一种基于逆向传输机制的反馈型两级交换结构(FRTM-TSA)。该结构通过crossbar逆向传输机制使得任意输入端口均可获得其相邻端口的调度结果并以此对目标端口所反馈的缓存信息进行修正,基于修正后的信息进行算法调度使得FRTM-TSA能够避免信元冲突和信元失序,也无需在输出端口设置重排序缓存。理论分析和仿真结果均表明FRTM-TSA能够以相对简洁的交换结构和交换流程获得更优的时延性能。     

基于帧填补的MMM Clos网络按序分组交换算法

与其它类型的Clos网络相比,各级带缓存的MMM(Memory-Memory-Memory)Clos网络使得交换网络的配置时间最小化,但是MMM交换中间级缓存的存在会引起输出端口的信元乱序。该文提出了一种满帧填补扩展算法(EPF),采用逐帧转发的方式来避免MMM Clos网络中的乱序问题。新算法在输入级和输出级采用固定周期轮转方式,中间级采用最早信元优先输出调度,具有复杂度低,可分布式控制,以及不需要缓存加速的特点。分析和仿真结果表明该算法是稳定的,即输入输出为可允许业务时,算法可达100%吞吐率。     

星载Clos网络的全分布式容错调度算法

针对星载交换结构受空间辐射影响造成的可靠性严重下降问题,该文提出了一种支持全分布式调度的三级Clos网络及其全分布式容错(Fully Distributed Fault Tolerant, FDFT)调度算法,以提高星载交换结构在交叉点故障下的容错能力。该Clos网络的中间级和输出级采用联合输入交叉点队列,以支持Clos网络和交换单元内部的全分布式调度。FDFT采用一种分布式故障检测算法获得交叉点故障信息。基于对交叉点故障影响范围的分析,FDFT在输入级采用一种容错信元分发算法,实现无故障路径的负载均衡。理论分析证明,当任一输入/输出级交换单元故障个数不超过(m-n)或所有中间级交换单元故障个数不超过(m-n)时,其中m, n分别为输入级交换单元输入、输出端口数,FDFT能够达到100%吞吐率。仿真结果进一步验证,故障随机发生情况下,FDFT能够抵抗比故障任意发生情况下更多的故障,且在不同的业务场景下具有良好的吞吐率和时延性能。     

FIFO交换网络:一种保持信元次序完整性的多路径ATM交换结构

本文提出了一种新型的自选路由ＡＴＭ多路径交换结构，采用虚拟ＦＩＦＯ缓冲器技术，即能保持信元次序的完整性，又避免了螺旋式交换结构中虚拟信元引起的饱和吞吐量、延迟和信元丢失性能的下降。在均匀通信量和非均匀通信量情况下分析了它的性能，结果表明其最大可达到的饱和吞吐量为７／８，延迟和信元丢失率都比螺旋式结构小很多。同时，该系统无需内部加速，适于ＶＬＳＩ集成。     

星上交换系统输入缓存调度算法

为改善星上交换系统的性能,该文提出了一种新的输入缓存调度算法。该算法基于Crossbar交换结构,采用了串行调度思想,在兼顾每个端口公平性的基础上调整了输出端口的仲裁策略,增加了端口匹配的概率。该算法大大减小了调度时延和丢失率。分析与仿真结果表明,该算法在平均调度时延和信元丢失率等方面的性能指标均优于已有算法而且实现复杂度不增加。     

一种基于Credit的变长分组并行交换网络调度算法

该文提出了一种新的并行分组交换(PPS)网络调度算法。该算法通过在解复用器处采用以变长分组为业务分配单元的方式消除了信元的乱序问题;通过采用Credit机制进行业务分配,实现了业务到各个交换平面完全公平的分配;各个并行交换单元采用组合输入输出排队,降低了对缓存和交换平面的加速要求,同时可以充分利用现有单Crossbar网络调度算法的研究成果。文中证明了该算法对业务分配的公平性,对高速缓存的需求量以及整个网络的稳定性,仿真进一步证明了该算法具有良好性能。     

一种新的高性能ATM共享存储交换单元

ATM交换单元中．可选用三种基本排队策略一输入捧队、输出捧队和共享存贮捧队。根据平均信元时延、吞吐量和信元丢失概率性能．最佳的排队策略是共享存储捧队。由于传统的共享存储交换单元必须缓冲经过交换单元的所有信元，因此交换单元的吞吐量和信元丢失概率性能仍不理想，特别是对于大规模交换单元情况更是如此。本文提出了一种新的高性能共享存储交换单元，称为阻塞信元共享存储（BCSM)交换单元。顾名思义，BCSM仅仅缓冲交换单元输入端口的阻塞信元，而不必缓冲经过交换单元的所有信元。均匀业务下的分析结果证明，BCSM交换单元比一般共享存贮交换单元具有更好的性能。     

一种改进的反馈制两级交换结构FTSA-2-SS

基于反馈的两级交换结构FTSA (Feedback-based Two-stage Switch Architecture)在仿真中表现出极其优异的时延性能,但该结构对调度算法的时间限制使其理论性能无法实现。针对这一问题,该文基于2-错列对称的crossbar连接模式提出一种改进的反馈制两级交换结构FTSA-2-SS (FTSA using the 2-Staggered Symmetry connection pattern),应用该连接模式可使信元传输与调度算法并行工作,从而将算法的时域空间拓展到一个时槽。此外,该文还利用双信元缓冲模式和RB (Re-sequencing Buffer)来解决由此而带来的信元冲突和失序问题。理论分析表明FTSA-2-SS和FTSA具有相同的稳定性,仿真结果显示FTSA-2-SS的时延性能优于其他非反馈负载均衡结构。     

基于前置反馈的两级交换结构

为缓解FTSA(feedback-based two-stage switch architecture)对调度算法的时间限制,提出一种基于前置反馈的两级交换结构FFTS(front-feedback-based two-stage switch architecture),该结构通过将反馈操作提前到信元传输之前的方法实现了信元传输与调度算法并行工作,拓展了调度算法的时域空间。此外FFTS还利用双信元缓冲模式和重排序缓存解决由此而带来的信元冲突和失序问题。仿真和分析表明FFTS的时延性能优于其他非反馈制负载均衡结构。     

多维分组交换结构中的一种缓存设置方法

分析了在多维分组交换结构（MPSF, multi-dimensional packet switching fabric）中,采用传统的缓存设置方法时存在的缺陷.为此,提出了一种新的缓存设置方法.该方法可简化交换节点调度策略的实现,提升交换结构的吞吐量.分析和仿真结果验证,相比与传统的在MPP （massively parallel processor）中采用的缓存设置方法,采用新方法可获得更好的吞吐量性能,且降低实际开销.     

两级交换机中分组有序到达算法研究

为了提高高性能分组交换机的扩展性,张尚正等人提出了一种称为负载平衡交换机(load-balancedswitch)的交换结构,该交换机分为两级交换结构,每一级都采用一种时序固定的连接方式,具有良好的扩展性;同时可以提供100%吞吐量保证。但是,负载平衡交换机的基本结构会出现分组乱序的情况。本文提出了一种在两级负载平衡交换机中保证分组顺序到达的满帧填充算法,该算法具有良好的交换特性(平均时延及吞吐量),同时也是一种分布式算法,各个端口可以独立地进行操作。     

A Novel Algorithm for Maintaining Packet Order in Two‐Stage Switches

To enhance the scalability of high performance packet switches, a two‐stage load‐balanced switch has recently been introduced, in which each stage uses a deterministic sequence of configurations. The switch is simple to make scalable and has been proven to provide 100% throughput. However, the load‐balanced switch may missequence the packets. In this paper, we propose an algorithm called full frame stuff (FFS), which maintains packet order in the two‐stage load‐balanced switch and has excellent switching performance. This algorithm is distributed and each port can operate independently.     

RED分组丢弃算法性能研究

 本文研究了在ATM交换机上实现的RED算法的性能.在固定有效带宽、时变有效带宽情况下和同种、异种业务环境下,研究了RED算法的通过率、公平性和时延等性能.经研究表明:RED算法有必要与EPD算法相结合,构成RED+EPD算法.采用RED+EPD算法的ATM交换机通过控制平均排队长度,有效地减小了交换机的平均排队时延.通过与其他分组丢弃算法进行性能比较表明:采用RED+EPD算法的ATM交换机,可提供比EPD算法略高的通过率,更好的公平性和更低的排队时延,能较好地支持具有时延要求的业务.     

一种公平输入排队调度算法

输入排队交换结构以其良好的可扩展性被越来越多的高速交换机和路由器所采用。当前的调度算法大都以牺牲公平性来换取最大的吞吐量。但随着对QoS支持的要求增强,适用于输入排队交换结构的高效、公平的调度算法成为迫切需要解决的问题。该文提出了一种具有公平性保证的基于虚服务量的公平调度算法。理论分析和计算机仿真都表明算法在信元时延和公平性方面都能提供较好的保证。算法还具有与iSLIP相同的较低通信开销,以及和iLQF相同的算法复杂度。因此,算法具有较好的实用性。     

带偏射补偿机制的Birkhoff-von-Neumann交换机方案及其性能分析

Birkhoff-von-Neumann(BvN)交换机具有较低的执行复杂度和较高的吞吐量,但无法在业务突发的环境下提供性能保证。为此,提出一种带偏射的BvN(D-BvN)交换机制来增强交换机性能。D-BvN交换机通过平均业务矩阵的BvN分解,为每个虚电路(VC)提供均值带宽保证,同时通过偏射来处理业务突发。其主要思想是利用处于空闲状态的VC的闲置容量处理处于溢出状态的VC的溢出业务。具体地,偏射机制利用空闲VC的闲置容量完成两件事情:一是把溢出业务偏射到其他VC,二是给偏射业务提供到达目的端口的带宽。分析和仿真结果表明,所提方法不仅可以获得接近100%的输入负载吞吐量,而且具有较低的包乱序概率和较小的业务包延时。     

Rerouting network: a high-performance self-routing switch forB-ISDN

A high-performance self-routing switch is proposed for ATM (asynchronous transfer mode) switch systems. Switching performance is enhanced by a rerouting algorithm applied to a particular multistage interconnection algorithm. The interconnection algorithm offers many access points to the output and resolves output contention by layering buffers at each switching stage. The author analyzes switching performance and shows that this switch can be easily engineered to have high throughput and low cell loss probability by increasing the number of switching stages. The author also illustrates that the number of switching stages required for a given cell loss probability shows gradual growth with increasing switch size. Analysis shows that the proposed switch is robust even with respect to nonuniform traffic     

一种新型的负载均衡-交叉点缓冲交换结构

针对混合输入-交叉点队列(CICQ)交换结构受限于"流控通信延时"、"需要2倍内部加速仿真输出队列(OQ)交换"以及单纯交叉点缓冲(CQ)存在"非均衡流量模式下吞吐量性能不足"等问题,本文提出一种新型的"负载均衡交叉点缓冲交换结构".采用固定模式时隙轮转匹配进行负载均衡处理,将到达输入端口的非均衡流量转化为近似均衡流量并且平均分配到同一输出端口对应的交叉缓冲中,从而可以利用较小的交叉点缓冲来模拟输出队列调度,简化调度过程并且提高吞吐量.理论分析证明了这种新结构的稳定性以及模拟输出队列交换的能力.同时仿真表明,采用该交换结构可以在不需要内部加速的条件下获得相当于输出队列交换的性能,并且有效地解决了交叉点缓冲队列非均衡流量性能不足的问题.     

Design of wavelength converting switches for optical burst switching

Optical burst switching (OBS) is an experimental network technology that enables the construction of very high-capacity routers, using optical data paths and electronic control. In this paper, we study wavelength converting switches using tunable lasers and wavelength grating routers, that are suitable for use in OBS systems and evaluate their performance. We show how the routing problem for these switches can be formulated as a combinatorial puzzle or game, in which the design of the game board corresponds to the pattern of permutation used at the input sections of the switch. We use this to show how the permutation pattern affects the performance of the switch, and to facilitate the design of permutation patterns that yield the best performance. We give upper bounds on the number of different wavelength channels that can be routed through such switches (regardless of the permutation pattern), and show that for 2/spl times/2 switches, there is a simple permutation pattern that achieves these bounds. For larger switches, randomized permutation patterns produce the best results. We study the performance of optical burst switches using wavelength converting switches based on several different permutation patterns. We also present a novel routing algorithm called the most available wavelength assignment and evaluate its benefits in improving the switch throughput. Our results show that for a typical configuration, the switch with the best permutation pattern has more than 87% of the throughput of a fully nonblocking switch.     

A central-stage buffered three-stage Clos switching fabric and the scheduling algorithm

Current MSM switching fabric has poor performance under unbalanced traffic. This paper presents an alternative, novel Central-stage Buffered Three-stage Clos switching (CB-3Clos) fabric and proves that this fabric can emulate output queuing switch without any speedup. By analyzing the condition to satisfy the central-stage load-balance, this paper also proposes a Central-stage Load-balanced-based Distributed Scheduling algorithm (CLDS) for CB-3Clos. The results show that, compared with Concurrent Round-Robin based Dispatching (CRRD) algorithm based on MSM, CLDS algorithm has high throughput irrespective with the traffic model and better performance in mean packet delay.     

一种新型负载均衡交叉缓冲交换矩阵(英文)

The fast growth of Internet has created the need for high-speed switches. Recently, the crosspoint-queue switch has attracted attention because of its scalability and high performance. However, the Crosspoint-Queue switch does not perform well under non-uniform traffic. To overcome this limitation, the Load-Balanced Crosspoint-Queued switch architecture has been proposed. In this architecture, a load-balance stage is placed ahead of the Crosspoint-Queued stage. The load-balance stage transforms the incoming non-uniform traffic into nearly uniform traffic at the input port of the second stage. To avoid out-of-order cells, this stage employs flow-based queues in each crosspoint buffer. Analysis and simulation results reveal that under non-uniform traffic, this new switch architecture achieves a delay performance similar to that of the Output-Queued switch without the need for internal acceleration. In addition, its throughput is much better than that of the pure crosspoint-queued switch. Finally, it can achieve the same packet loss rate as the crosspoint-queue switch, while using a buffer size that is only 65% of that used by the crosspoint-queue switch.