The convergence and stability analysis for two end-to-end rate-based congestion control algorithms with unavoidable random loss in packets are presented, which can be caused by, for example, errors on wireless links. ...The convergence and stability analysis for two end-to-end rate-based congestion control algorithms with unavoidable random loss in packets are presented, which can be caused by, for example, errors on wireless links. The convergence rates of these two algorithms are analyzed by linearizing them around their equilibrium points, since they are globally stable and can converge to their unique equilibrium points. Some sufficient conditions for local stability in the presence of round-trip delay are obtained based on the general Nyquist criterion of stability. The stability conditions can be considered to be more general. If random loss in the first congestion control algorithm is not considered, they reduce to the local stability conditions which have been obtained in some literatures. Furthermore, sufficient conditions for local stability of a new congestion control algorithm have also been obtained if random loss is not considered in the second congestion control algorithm.展开更多
One of the more challenging and unresolved issues in ATM networks is the congestion control of available bit rate （ABR）. The dynamic controller is designed based on the control theory and the feedback mechanism of e...One of the more challenging and unresolved issues in ATM networks is the congestion control of available bit rate （ABR）. The dynamic controller is designed based on the control theory and the feedback mechanism of explicit rates With the given method of a chosen parameter, it can guarantee the stability of the controller and closed loop system with propagation delay and bandwidth oscillation. It needs less parameters（only one） to be designed. The queue length can converge to the given value in the least steps. The fairness of different connections is considered further. The simulations show better performance and good quality of service（QoS） is achieved.展开更多
The inherent selfishness of each node for the enhancement of message successful delivery ratio and the network overall performance improvement are reflected in the contradiction relationship of competition and coopera...The inherent selfishness of each node for the enhancement of message successful delivery ratio and the network overall performance improvement are reflected in the contradiction relationship of competition and cooperation in delay/disruption tolerant networks (DTN). In particular, the existence of malicious node aggravates this contradiction. To resolve this contradiction, social relationship theory and group theory of social psychology were adopted to do an in-depth analysis. The concrete balancing approach which leveraged Nash equilibrium theory of game theory was proposed to resolve this contradiction in reality. Thus, a new congestion control routing algorithm for security defense based on social psychology and game theory (CRSG) was put forward. Through the experiment, this algorithm proves that it can enhance the message successful delivery ratio by more than 15% and reduce the congestion ratio over 15% as well. This algorithm balances the contradiction relationship between the two key performance targets and made all nodes exhibit strong cooperation relationship in DTN.展开更多
The improved ERICA algorithm for ABR flow congestion control is presented based on available bandwidth prediction using the BP neural networks in ATM networks. The switch periodically calculates the available bandwidt...The improved ERICA algorithm for ABR flow congestion control is presented based on available bandwidth prediction using the BP neural networks in ATM networks. The switch periodically calculates the available bandwidth, monitors the load of network and updates the ER value according to the PERICA algorithm. The proposed algorithm can keep better performance than ERICA algorithm in simulations.展开更多
There were many contradictory evaluation criteria to select next-hop in the delay-disruption tolerance networks(DTN).To solve this problem,an attribute hierarchical model was proposed,in which the predefined criteria ...There were many contradictory evaluation criteria to select next-hop in the delay-disruption tolerance networks(DTN).To solve this problem,an attribute hierarchical model was proposed,in which the predefined criteria were summarized as static identity attributes,forwarding desire attributes and delivery capability attributes(IDC).Based on this model,a novel multi-attributes congestion aware routing(MACAR) scheme with uncertain information for next-hop selection was presented,by adopting an decision theory to aggregate attributes with belief structure and computing partial ordering relations.The simulation results show that MACAR presents higher successful delivery rate,lower average delay and effectively alleviate congestion.展开更多
The semi-round rigid feet would cause position-posture deviation problem because the actual foothold position is hardly known due to the rolling effect of the semi-round rigid feet during the robot walking. The positi...The semi-round rigid feet would cause position-posture deviation problem because the actual foothold position is hardly known due to the rolling effect of the semi-round rigid feet during the robot walking. The position-posture deviation problem may harm to the stability and the harmony of the robot, or even makes the robot tip over and fail to walk forward. Focused on the position-posture deviation problem of multi-legged walking robots with semi-round rigid feet, a new method of position-posture closed-loop control is proposed to solve the position-posture deviation problem caused by semi-round rigid feet, based on the inverse velocity kinematics of the multi-legged walking robots. The position-posture closed-loop control is divided into two parts: the position closed-loop control and the posture closed-loop control. Thus, the position-posture control for the robot which is a tight coupling and nonlinear system is decoupled. Co-simulations of position-posture open-loop control and position-posture closed-loop control by MATLAB and ADAMS are implemented, respectively. The co-simulation results verify that the position-posture closed-loop control performs well in solving the position-posture deviation problem caused by semi-round rigid feet.展开更多
跨数据中心网络是处于不同地区的数据中心网络(Data Center Networks,DCNs)通过广域网(Wide-Area Network,WAN)连接组成的网络,分布式应用通常基于该网络为用户提供高质量的服务。DCNs和WAN的缓冲区大小、往返时延存在显著差异,这导致...跨数据中心网络是处于不同地区的数据中心网络(Data Center Networks,DCNs)通过广域网(Wide-Area Network,WAN)连接组成的网络,分布式应用通常基于该网络为用户提供高质量的服务。DCNs和WAN的缓冲区大小、往返时延存在显著差异,这导致现有的Cubic拥塞控制算法在跨数据中心网络场景下出现降速不准确、丢包率过高以及与其他拥塞控制算法兼容性差等问题。针对以上挑战,提出了一种通过匹配不同发送速率模式的改进Cubic算法Cubic+。具体地,Cubic+整合了网络中的时延、ECN(Explicit Congestion Notification)和丢包信号。当拥塞发生在浅缓冲交换机时,Cubic+会周期性地排空队列;当拥塞发生在深缓冲路由器时,Cubic+会快速减少堆积的数据包。基于大规模NS3仿真实验结果表明,在跨数据中心网络流量模型下,Cubic+与现有流行算法相比,平均流完成时间最多减少了20.77%,第99百分位流完成时间最多减少了15.88%,为跨数据中心网络提供了一种高吞吐的拥塞控制算法。展开更多
算力供给的代际异构性与供应链安全需求,促使异构算力成为AI基础设施的新趋势。然而,在异构混合训练场景中,基于融合以太网的RDMA版本2(RDMA over converged Ethernet version 2,RoCEv2)方案存在负载均衡与拥塞控制缺陷,在模型训练的并...算力供给的代际异构性与供应链安全需求,促使异构算力成为AI基础设施的新趋势。然而,在异构混合训练场景中,基于融合以太网的RDMA版本2(RDMA over converged Ethernet version 2,RoCEv2)方案存在负载均衡与拥塞控制缺陷,在模型训练的并行通信中性能欠佳;而现有高性能同构智算网络方案因设备异构与集合通信库(collective communication library,CCL)闭源难以部署。为此,提出了面向异构算力场景的高性能智算网络解决方案——智能控制以太网(intelligent control Ethernet,ICE)。该方案基于RoCEv2协议体系,在避免对设备、CCL进行深度定制的前提下,将异构通信库信息采集、集中控制器与端侧自主控制相结合,实现全局最优路径规划及全局主动拥塞控制,显著提升异构并行通信性能。真实物理环境实验表明,ICE可提升集合通信性能最高达47%。ICE为异构智算网络建设提供了开创性、易部署的解决方案。展开更多
基金supported in part by the National Natural Science Foundation of China (10671170,60404022)the National Outstanding Youth Foundation of China (60525303)and the Natural Science Foundation of Hebei Province (07M005,F2008000864)
文摘The convergence and stability analysis for two end-to-end rate-based congestion control algorithms with unavoidable random loss in packets are presented, which can be caused by, for example, errors on wireless links. The convergence rates of these two algorithms are analyzed by linearizing them around their equilibrium points, since they are globally stable and can converge to their unique equilibrium points. Some sufficient conditions for local stability in the presence of round-trip delay are obtained based on the general Nyquist criterion of stability. The stability conditions can be considered to be more general. If random loss in the first congestion control algorithm is not considered, they reduce to the local stability conditions which have been obtained in some literatures. Furthermore, sufficient conditions for local stability of a new congestion control algorithm have also been obtained if random loss is not considered in the second congestion control algorithm.
基金This project was supported partly by the Outstanding Youth Scientific Foundation of China(60525303)the National Natural Science Foundation of China(60404022, 60604012)the Natural Science Foundation of Hebei Province of China(F2005000390).
文摘One of the more challenging and unresolved issues in ATM networks is the congestion control of available bit rate （ABR）. The dynamic controller is designed based on the control theory and the feedback mechanism of explicit rates With the given method of a chosen parameter, it can guarantee the stability of the controller and closed loop system with propagation delay and bandwidth oscillation. It needs less parameters（only one） to be designed. The queue length can converge to the given value in the least steps. The fairness of different connections is considered further. The simulations show better performance and good quality of service（QoS） is achieved.
基金Projects(61202488, 61070199, 61103182) supported by the National Natural Science Foundation of China
文摘The inherent selfishness of each node for the enhancement of message successful delivery ratio and the network overall performance improvement are reflected in the contradiction relationship of competition and cooperation in delay/disruption tolerant networks (DTN). In particular, the existence of malicious node aggravates this contradiction. To resolve this contradiction, social relationship theory and group theory of social psychology were adopted to do an in-depth analysis. The concrete balancing approach which leveraged Nash equilibrium theory of game theory was proposed to resolve this contradiction in reality. Thus, a new congestion control routing algorithm for security defense based on social psychology and game theory (CRSG) was put forward. Through the experiment, this algorithm proves that it can enhance the message successful delivery ratio by more than 15% and reduce the congestion ratio over 15% as well. This algorithm balances the contradiction relationship between the two key performance targets and made all nodes exhibit strong cooperation relationship in DTN.
文摘The improved ERICA algorithm for ABR flow congestion control is presented based on available bandwidth prediction using the BP neural networks in ATM networks. The switch periodically calculates the available bandwidth, monitors the load of network and updates the ER value according to the PERICA algorithm. The proposed algorithm can keep better performance than ERICA algorithm in simulations.
基金Project(60973127) supported by the National Natural Science Foundation of ChinaProject(09JJ3123) supported by the Natural Science Foundation of Hunan Province,China
文摘There were many contradictory evaluation criteria to select next-hop in the delay-disruption tolerance networks(DTN).To solve this problem,an attribute hierarchical model was proposed,in which the predefined criteria were summarized as static identity attributes,forwarding desire attributes and delivery capability attributes(IDC).Based on this model,a novel multi-attributes congestion aware routing(MACAR) scheme with uncertain information for next-hop selection was presented,by adopting an decision theory to aggregate attributes with belief structure and computing partial ordering relations.The simulation results show that MACAR presents higher successful delivery rate,lower average delay and effectively alleviate congestion.
基金Project(51221004)supported by the Science Fund for Creative Research Groups of National Natural Science Foundation of ChinaProject supported by the Program for Zhejiang Leading Team of S&T Innovation,China
文摘The semi-round rigid feet would cause position-posture deviation problem because the actual foothold position is hardly known due to the rolling effect of the semi-round rigid feet during the robot walking. The position-posture deviation problem may harm to the stability and the harmony of the robot, or even makes the robot tip over and fail to walk forward. Focused on the position-posture deviation problem of multi-legged walking robots with semi-round rigid feet, a new method of position-posture closed-loop control is proposed to solve the position-posture deviation problem caused by semi-round rigid feet, based on the inverse velocity kinematics of the multi-legged walking robots. The position-posture closed-loop control is divided into two parts: the position closed-loop control and the posture closed-loop control. Thus, the position-posture control for the robot which is a tight coupling and nonlinear system is decoupled. Co-simulations of position-posture open-loop control and position-posture closed-loop control by MATLAB and ADAMS are implemented, respectively. The co-simulation results verify that the position-posture closed-loop control performs well in solving the position-posture deviation problem caused by semi-round rigid feet.
文摘算力供给的代际异构性与供应链安全需求,促使异构算力成为AI基础设施的新趋势。然而,在异构混合训练场景中,基于融合以太网的RDMA版本2(RDMA over converged Ethernet version 2,RoCEv2)方案存在负载均衡与拥塞控制缺陷,在模型训练的并行通信中性能欠佳;而现有高性能同构智算网络方案因设备异构与集合通信库(collective communication library,CCL)闭源难以部署。为此,提出了面向异构算力场景的高性能智算网络解决方案——智能控制以太网(intelligent control Ethernet,ICE)。该方案基于RoCEv2协议体系,在避免对设备、CCL进行深度定制的前提下,将异构通信库信息采集、集中控制器与端侧自主控制相结合,实现全局最优路径规划及全局主动拥塞控制,显著提升异构并行通信性能。真实物理环境实验表明,ICE可提升集合通信性能最高达47%。ICE为异构智算网络建设提供了开创性、易部署的解决方案。
