在无线局域网络中,针对无线信道的异构性和传输控制协议(transmission control protocol,TCP)闭环拥塞控制的贪婪性,提出了一种基于显式拥塞通告(explicit congestion notification,ECN)标记算法的公平拥塞控制机制(access point conges...在无线局域网络中,针对无线信道的异构性和传输控制协议(transmission control protocol,TCP)闭环拥塞控制的贪婪性,提出了一种基于显式拥塞通告(explicit congestion notification,ECN)标记算法的公平拥塞控制机制(access point congestion control,APCC)。APCC在AP节点结合缓存队列长度和无线信道负载的测量来检测拥塞,依据联合的拥塞测度来实施拥塞控制,通过保证低丢包率和低排队延时得到了高吞吐率;利用ECN显式反馈机制,对通过AP的上行和下行TCP DATA和ACK分组实施ECN标记,实现了上下行公平的双向拥塞控制;同时在多速率信道环境下,依据各流的无线信道速率来调节单流ECN的标记概率,实现不同无线信道速率TCP流之间的时间公平,大大提高了网络的总体效率。展开更多
According to the Wide Area Network model, we formulate Internet flow control as a constrained convex programming problem, where the objective is to maximize the total utility of all sources over their transmission rat...According to the Wide Area Network model, we formulate Internet flow control as a constrained convex programming problem, where the objective is to maximize the total utility of all sources over their transmission rates. Based on this formulation, flow control can be converted to a normal unconstrained optimization problem through the barrier function method, so that it can be solved by means of a gradient projection algorithm with properly rate iterations. We prove that the algorithm converges to the global optimal point, which is also a stable proportional fair rate allocation point, provided that the step size is properly chosen. The main difficulty facing the realization of iteration algorithm is the distributed computation of congestion measure. Fortunately, Explicit Congestion Notification (ECN) is likely to be used to improve the performance of TCP in the near future. By using ECN, it is possible to realize the iteration algorithm in IP networks. Our algorithm is divided into two parts, algorithms in the router and in the source. The router marks the ECN bit with a probability that varies as its buffer occupancy varies, so that the congestion measure of links can be communicated to the source when the marked ECN bits are reflected back from its destination. Source rates are then updated by all sessions according to the received congestion measure. The main advantage of our scheme is its fast convergence ability and robustness; it can also provide the network with zero packet loss by properly choosing the queue threshold and provide differentiated service to users by applying different utility functions.展开更多
Bursty traffic and thousands of concurrent flows incur inevitable network congestion in datacenter networks(DCNs)and then affect the overall performance.Various transport protocols are developed to mitigate the networ...Bursty traffic and thousands of concurrent flows incur inevitable network congestion in datacenter networks(DCNs)and then affect the overall performance.Various transport protocols are developed to mitigate the network congestion,including reactive and proactive protocols.Reactive schemes use different congestion signals,such as explicit congestion notification(ECN)and round trip time(RTT),to handle the network congestion after congestion arises.However,with the growth of scale and link speed in datacenters,reactive schemes encounter a significant problem of slow responding to congestion.On the contrary,proactive protocols(e.g.,credit-reservation protocols)are designed to avoid congestion before it occurs,and they have the advantages of zero data loss,fast convergence and low buffer occupancy.But credit-reservation protocols have not been widely deployed in current DCNs(e.g.,Microsoft,Amazon),which mainly deploy ECN-based protocols,such as data center transport control protocol(DCTCP)and data center quantized congestion notification(DCQCN).And in an actual deployment scenario,it is hard to guarantee one protocol to be deployed in every server at one time.When credit-reservation protocol is deployed to DCNs step by step,the network will be converted to multi-protocol state and will face the following fundamental challenges:1)unfairness,2)high buffer occupancy,and 3)heavy tail latency.Therefore,we propose Harmonia,aiming for converging ECN-based and credit-reservation protocols to fairness with minimal modification.To the best of our knowledge,Harmonia is the first to address the trouble of harmonizing proactive and reactive congestion control.Targeting the common ECN-based protocols-DCTCP and DCQCN,Harmonia leverages forward ECN and RTT to deliver real-time congestion information and redefines feedback control.After the evaluation,the results show that Harmonia effectively solves the unfair link allocation,eliminating the timeouts and addressing the buffer overflow.展开更多
Ad hoc网络是一种对等式网络，使用无线通信技术，节点可移动。Ad hoc网络拓扑的频繁变化导致了分组的大量丢失，会被TCP认为是网络发生拥塞，不正确的引发拥塞控制，从而引起吞吐量的急剧下降。使用基于反馈的体系结构与显式的报文通...Ad hoc网络是一种对等式网络，使用无线通信技术，节点可移动。Ad hoc网络拓扑的频繁变化导致了分组的大量丢失，会被TCP认为是网络发生拥塞，不正确的引发拥塞控制，从而引起吞吐量的急剧下降。使用基于反馈的体系结构与显式的报文通知机制可以有效地克服这一问题。对已有的方法进行比较研究。展开更多
现有的TCP协议采用丢包事件、拥塞反馈信息或往返时延等信息启动拥塞控制,而这些基于单个数据包信息的方法进行丢包区分的能力较弱,使得有线/无线混合网络中的非拥塞丢包影响了TCP的拥塞控制行为.本文提出了一种新的TCP协议,PceReno(Pro...现有的TCP协议采用丢包事件、拥塞反馈信息或往返时延等信息启动拥塞控制,而这些基于单个数据包信息的方法进行丢包区分的能力较弱,使得有线/无线混合网络中的非拥塞丢包影响了TCP的拥塞控制行为.本文提出了一种新的TCP协议,PceReno(Probability of Congestion or Error),它通过对最近一段数据的拥塞概率预测来决定如何响应当前丢包事件,从而避免盲目的启动拥塞控制.这种先应式拥塞感知和后应式拥塞响应相结合的拥塞控制方法不需要增加额外的开销,完全依赖于原有的拥塞控制.实验结果表明PceReno能够较好地对抗随机错误,有效提高TCP在混合网络中的吞吐量.展开更多
文摘在无线局域网络中,针对无线信道的异构性和传输控制协议(transmission control protocol,TCP)闭环拥塞控制的贪婪性,提出了一种基于显式拥塞通告(explicit congestion notification,ECN)标记算法的公平拥塞控制机制(access point congestion control,APCC)。APCC在AP节点结合缓存队列长度和无线信道负载的测量来检测拥塞,依据联合的拥塞测度来实施拥塞控制,通过保证低丢包率和低排队延时得到了高吞吐率;利用ECN显式反馈机制,对通过AP的上行和下行TCP DATA和ACK分组实施ECN标记,实现了上下行公平的双向拥塞控制;同时在多速率信道环境下,依据各流的无线信道速率来调节单流ECN的标记概率,实现不同无线信道速率TCP流之间的时间公平,大大提高了网络的总体效率。
文摘According to the Wide Area Network model, we formulate Internet flow control as a constrained convex programming problem, where the objective is to maximize the total utility of all sources over their transmission rates. Based on this formulation, flow control can be converted to a normal unconstrained optimization problem through the barrier function method, so that it can be solved by means of a gradient projection algorithm with properly rate iterations. We prove that the algorithm converges to the global optimal point, which is also a stable proportional fair rate allocation point, provided that the step size is properly chosen. The main difficulty facing the realization of iteration algorithm is the distributed computation of congestion measure. Fortunately, Explicit Congestion Notification (ECN) is likely to be used to improve the performance of TCP in the near future. By using ECN, it is possible to realize the iteration algorithm in IP networks. Our algorithm is divided into two parts, algorithms in the router and in the source. The router marks the ECN bit with a probability that varies as its buffer occupancy varies, so that the congestion measure of links can be communicated to the source when the marked ECN bits are reflected back from its destination. Source rates are then updated by all sessions according to the received congestion measure. The main advantage of our scheme is its fast convergence ability and robustness; it can also provide the network with zero packet loss by properly choosing the queue threshold and provide differentiated service to users by applying different utility functions.
基金supported by the National Key Research and Development Program of China under Grant No.2018YFB0204300the National Postdoctoral Program for Innovative Talents under Grant No.BX20190091Excellent Youth Foundation of Hunan Province(De-Zun Dong).
文摘Bursty traffic and thousands of concurrent flows incur inevitable network congestion in datacenter networks(DCNs)and then affect the overall performance.Various transport protocols are developed to mitigate the network congestion,including reactive and proactive protocols.Reactive schemes use different congestion signals,such as explicit congestion notification(ECN)and round trip time(RTT),to handle the network congestion after congestion arises.However,with the growth of scale and link speed in datacenters,reactive schemes encounter a significant problem of slow responding to congestion.On the contrary,proactive protocols(e.g.,credit-reservation protocols)are designed to avoid congestion before it occurs,and they have the advantages of zero data loss,fast convergence and low buffer occupancy.But credit-reservation protocols have not been widely deployed in current DCNs(e.g.,Microsoft,Amazon),which mainly deploy ECN-based protocols,such as data center transport control protocol(DCTCP)and data center quantized congestion notification(DCQCN).And in an actual deployment scenario,it is hard to guarantee one protocol to be deployed in every server at one time.When credit-reservation protocol is deployed to DCNs step by step,the network will be converted to multi-protocol state and will face the following fundamental challenges:1)unfairness,2)high buffer occupancy,and 3)heavy tail latency.Therefore,we propose Harmonia,aiming for converging ECN-based and credit-reservation protocols to fairness with minimal modification.To the best of our knowledge,Harmonia is the first to address the trouble of harmonizing proactive and reactive congestion control.Targeting the common ECN-based protocols-DCTCP and DCQCN,Harmonia leverages forward ECN and RTT to deliver real-time congestion information and redefines feedback control.After the evaluation,the results show that Harmonia effectively solves the unfair link allocation,eliminating the timeouts and addressing the buffer overflow.
文摘现有的TCP协议采用丢包事件、拥塞反馈信息或往返时延等信息启动拥塞控制,而这些基于单个数据包信息的方法进行丢包区分的能力较弱,使得有线/无线混合网络中的非拥塞丢包影响了TCP的拥塞控制行为.本文提出了一种新的TCP协议,PceReno(Probability of Congestion or Error),它通过对最近一段数据的拥塞概率预测来决定如何响应当前丢包事件,从而避免盲目的启动拥塞控制.这种先应式拥塞感知和后应式拥塞响应相结合的拥塞控制方法不需要增加额外的开销,完全依赖于原有的拥塞控制.实验结果表明PceReno能够较好地对抗随机错误,有效提高TCP在混合网络中的吞吐量.
文摘提出一种基于延迟探测机制的算法,该算法通过探测分组在瓶颈网关队列中的延迟时间来估计网络的拥塞状况,设置一个探测门限。当分组的排队延迟超过门限时,采用显式拥塞指示(explicit congestion notification,ECN)机制标记分组以向传输控制协议(transport control protocol,TCP)源端通知拥塞。为了使该算法在网关中更易实现且具有自适应性,算法在每个周期中都根据不同TCP流对网关资源的占用情况来评估其权重,然后选取权重最大的若干TCP流的测量结果来更新拥塞探测门限,使网关对于突发流量在达到高吞吐量、高链路利用率和稳定的平均队列长度的同时,能更公平地分配资源。通过ns-2下的仿真,证明算法能达到预期的效果。
