Combined Input-crosspoint-queued Research Articles

A Practical Large-Capacity Three-Stage Buffered Clos-Network Switch Architecture

This paper proposes a three-stage buffered Clos-network switch (TSBCS) architecture along with a novel batch scheduling (BS) mechanism. We found that TSBCS/BS can be mapped to a “fat” combined input-crosspoint queued (CICQ) switch. Consequently, the well-studied CICQ scheduling algorithms can be directly applied in TSBCS. Moreover, BS drastically reduces the time complexity of TSBCS scheduling when compared with ordinary CICQ switches of the same number of switch ports, which enables us to build a larger-capacity switch with reasonable scheduling complexity. We further show that TSBCS/BS can achieve 100 percent throughput under any admissible traffic if a stable CICQ scheduling algorithm is used. Direct cell forwarding schemes are proposed to overcome the performance drawback of BS under light traffic loads. With extensive simulations, we show that the performance of TSBCS/BS is comparable to that of output-queued switches and the latter are usually considered as theoretical optimal.

OpenFlow-Based Flow-Level Bandwidth Provisioning for CICQ Switches

Flow-level bandwidth provisioning (FBP) achieves fine-grained bandwidth assurance for individual flows. It is especially important for virtualization-based computing environments such as data centers. However, existing flow-level bandwidth provisioning solutions suffer from a number of drawbacks, including high implementation complexity, poor performance guarantees, and inefficiency to process variable length packets. In this paper, we study flow-level bandwidth provisioning for Combined Input Crosspoint Queued (CICQ) switches in the OpenFlow context. First, we propose the Flow-level Bandwidth Provisioning algorithm for CICQ switches, which reduces the switch scheduling problem to multiple instances of fair queuing problems, each utilizing a well-studied fair queuing algorithm. We theoretically prove that FBP can closely emulate the ideal Generalized Processing Sharing model, and accurately guarantee the provisioned bandwidth. Furthermore, we implement FBP in the OpenFlow software switch to obtain realistic performance data by a prototype. Leveraging the capability of OpenFlow to define and manipulate flows, we experimentally demonstrate a practical flow-level bandwidth provisioning solution. Finally, we conduct extensive simulations and experiments to evaluate the design. The simulation data verify the correctness of the analytical results, and show that FBP achieves tight performance guarantees. The experiment results demonstrate that our OpenFlow-based prototype can conveniently and accurately provision bandwidth at the flow level.

Interleaving Coded Multi-Threshold Scheduling Algorithm

PDF HTML阅读 XML下载 导出引用 引用提醒 一种交错编码的多重门限调度算法 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 High-Tech Research and Development Plan of China under Grant Nos.2007AA01Z218, 2008AA01Z214 (国家高技术研究发展计划(863)); the National Basic Research Program of China under Grant No.2007CB307102 (国家重点基础研究发展计划(973)) Interleaving Coded Multi-Threshold Scheduling Algorithm 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:提出一种交错编码的多重门限调度算法(interleaving coded multi-threshold scheduling,简称ICMTS).该算法将前、后级队列门限标记交错编码作为权值表征输入调度过程前、后两级队列的整体调度需求,根据交错编码的权值对前级虚拟输出队列进行优化调度判决,并通过多重门限机制降低算法的硬件资源开销.采用流模型证明当加速因子为2时,ICMTS算法可获得100%的吞吐量,并给出ICMTS算法的工程简化设计方案,复杂度为O(logN).仿真仿真结果表明,采用ICMTS算法的工程简化方案即可获得比现有算法更优的调度性能. Abstract:An interleaving coded multi-threshold scheduling (ICMTS) algorithm is proposed in this paper. Since the ICMTS algorithm uses the interleaving coded thresholds of two stage queues as the scheduling weights, it can systematically evaluate the scheduling demands of both the input queues and the crosspoint queues. By segmenting the queue length as multiple thresholds, the hardware resource of this algorithm can be largely decreased. It is proved that a CICQ (combined input-crosspoint-queued) switch operating with the ICMTS algorithm can achieve 100% throughput with a speedup of two. To facilitate hardware implementation, a simplified maximal ICMTS scheme is also presented with a time complexity of O(logN). Simulation results show that even the simplified ICMTS scheme can obtain better performance than the existing algorithms. 参考文献 相似文献 引证文献

A Distributed DiffServ Supporting Scheduling Algorithm

PDF HTML阅读 XML下载 导出引用 引用提醒 一种支持DiffServ模型的全分布式调度算法 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.60572042 (国家自然科学基金); the National High-Tech Research and Development Plan of China under Grant No.2005AA121210 (国家高技术研究发展计划(863)); the National Basic Research Program of China under Grant No.2007CB307102 (国家重点基础研究发展计划(973)) A Distributed DiffServ Supporting Scheduling Algorithm 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:调度算法设计对于网络路由设备实现区分服务(DiffServ)模型的单跳行为(per hop behavior,简称PHB)至关重要.现有支持DiffServ模型的调度算法普遍基于输出排队(output queued,简称OQ)或是输入排队(input queued,简称IQ)交换结构进行设计,均无法在高速环境下提供高性能的调度.基于联合输入/交叉节点排队(combined input-crosspoint-queued,简称CICQ)交换结构提出一种支持DiffServ模型的全分布式调度算法DDSS (distributed DiffServ supporting scheduling),并通过理论分析对其公平性进行了验证.DDSS算法采用基于预约带宽的逐级流量控制机制实现所有预约带宽在快速转发(expedited forwarding,简称EF)业务与确保转发(assured forwarding,简称AF)业务之间的分配,采用优先级调度机制为EF业务提供低延迟服务,算法复杂度为O(log N).仿真结果表明,DDSS算法具有良好的时延性能和公平特性,与现有算法相比,能够更好地支持DiffServ模型. Abstract:Scheduling algorithm is very important for network design to implement per hop behaviors (PHBs) in DiffServ model. Most of the presented DiffServ supporting scheduling algorithms are based on output queued (OQ) switches or input queued (IQ) switches, which are not suitable to be used in high speed network. This paper proposes a distributed DiffServ supporting scheduling (DDSS) algorithm based on combined input-crosspoint -queued (CICQ) switches. Theoretical analysis illuminates that the DDSS algorithm can obtain good fairness. The DDSS algorithm adopts a two-stage flow control mechanism based on periodic statistic to achieve fair bandwidth allocation for expedited forwarding (EF) and assured forwarding (AF) traffic, and uses a priority scheduling mechanism to provide lower delay for EF traffic. The time complexity of the DDSS algorithm is only O(log N), hence is practical and scalable for high speed network. Simulation results show that DDSS algorithm can obtain good fairness and delay performance. It is more appropriate to be used to support the DiffServ model. 参考文献 相似文献 引证文献

A non-uniform traffic oriented scheduling algorithm in combined input-crosspoint-queued (CICQ) switches

Combined input-crosspoint-queued (CICQ) switch structure decouples the inputs and outputs matching and enables totally distributed arbitration. CICQ switch cannot achieve 100% throughput under non-uniform traffic if Round-Robin (RR-RR) algorithm is used. The other existing schemes require quite a bit of hardware and time complexity. In this paper, we theoretically prove that the RR-RR can achieve 100% throughput under uniform traffic, but it would be instable under non-uniform traffic. Our quantitative analysis also points out that the throughput will be < 91.7% under the weak diagonal traffic model with f = 0.5 and k = 2, where f is the packet arrival rate along the main diagonal of the traffic matrix and k is the number of buffers used in each crosspoint. Moreover, our formula shows that the k must be at least 4 and 24, respectively, if we wish to improve the throughput to 95 and 99%. Based on our theoretical study, we propose the Differential Round-Robin (DRR) algorithm. Simulations have demonstrated that DRR can achieve 100% throughput under arbitrary traffic using only one buffer cell in each crosspoint. DRR algorithm keeps the high simplicity and efficiency of RR-RR with O(1) complexity while overcoming the instability problem of RR-RR.