按最小速率分配的ABR控制算法公平性的研究

现有和各种ＡＢＲ拥塞控制算法都只能实现最大最小准则下的公平分配。文中提出了一种称为“既得利益”相等的设计思想。依据这一思想改造现有算法,原则上可以在原算法框架内实现任一准则下的公平性。作为例子,我们改造了ＥＲＩＣＡ算法,使得新算法能达到ＡＴＭ论坛定义的按ＭＣＲ成比例分配带宽准则下的公平性。仿真实验结果表明,新算法性能良好。     

一种新的适用于多种公平准则的ABR流控算法的设计和研究

现有的各种ABR拥塞控制算法都只能实现最大最小准则下的公平性。本文提出了一种称为动态带宽分配(DBA)的控制算法,在该算法框架内可以方便地实现ATM论坛定义的任一准则下的公平性。仿真实验结果表明,新算法性能良好。     

效用max—min公平准则及其在ABR业务中的应用

本文提出一种新的基于效用函数的max-min(UMM）公平准则,它实现的是用户效用之间的公平分配。在ABR业务下,本文提出UMM公平性的另外两个等价定义,考察了用户的最小需求和最大需求。为了求解UMM公平分配,文中给出集中式的UMM公平分配算法及其数学证明。文章从保证分配效率的角度出发赋予峰值信元位率PCR以新的含义。UMM公平性不仅是对以往ABR业务中max-min公平性的概括,还具有很好的推广前景,特别适用于多应用类型的网络资源分配。     

一种新型的ABR流量控制算法

提出了一种基于随动系统的ABR流量控制算法，该算法应用了跟踪系统的反馈机制，通过检验缓存中的队列长度来控制源端速率。理论证明，这种算法不仅提高了缓存的利用率，同时大大降低了信元丢失率，以及拥塞产生的可能。仿真结果表明，该算法在实际应用中也是可行的。     

Parameter tuning of rate-based congestion control algorithm for ABR service class in ATM networks

A rate-based congestion control algorithm has been developed and standardized in the ATM forum for ABR service class. In the standard the behaviour of source and destination end systems is specified by several control parameters such as RIF (rate increase factor) and RDF (rate decrease factor). In spite of the fact that the performance of the rate-based congestion control algorithm depends heavily on the selection of these control parameters, no selection method of parameters is shown in the standard. In this paper, by extending our previous work, appropriate settings of rate-control parameters in the various circumstances are investigated. We first analyse the dynamical behaviour of the rate-based congestion control for multiple groups of ABR connections with different propagation delays. Next we evaluate the effect of CBR traffic on ABR connections. Simulation results for a multihop network configuration are also presented to exhibit the trade-off relationship among cell loss probability, link utilization and fairness. Finally, a selection method of control parameters in the multihop network is proposed based on our analytic methods and simulation results © 1998 John Wiley & Sons, Ltd.     

一种参数自适应的ABR业务流量控制算法

在对二进制ABR流量控制算法建模的基础上，得出缓存队列长度与相关参数的关系。根据这种关系，经过比较分析，提出一种参数自适应算法，通过动态选择Nnm值，加快了网络对拥塞的响应速度。仿真表明，该算法在减轻振荡、快速解除拥塞以及减小对缓存的依赖方面有着良好的性能。     

Adaptive ABR congestion control with active buffer control

ATM Forum has defined that the ABR service is designed mainly for data traffic. The design of a simple and efficient congestion control scheme is a problem that network managers have to face. In this paper, we propose a control scheme for ABR service for better scalability and response. The scheme uses both the load level and an increase in queue length to detect the presence of congestion. Continuous control functions are designed for the bandwidth allocation. A better buffer control is achieved by incorporating the percentage of buffer occupancy into the control function. All of the control functions are designed in such a way that they are sensitive to the change of the system states when they are far from the optimal level to get a fast response, but insensitive and change slowly when the states are close to the optimal level to keep the system around the steady state. Our simulation results show that the algorithm is fair to all the connections and it converges fast when the network's condition changes. Copyright © 2001 John Wiley & Sons, Ltd.     

一种新的用于ATM网中ABR点对多点连接的反馈合并算法

本文提出了一种新的用于ＡＴＭ网中的ＡＢＲ点对多点连接的反馈合并算法。新算法不仅能同时解决“合并噪声”和“合并延迟”问题,而且由于提供一种根据反向资源管理信元的ＣＩ域判断支路拥塞程度的机制,因此即使在ＥＲ交换机与二进制交换机并存的网络环境中仍然性能优越,这是现有算法所无法做到的。我们的仿真结果清楚地表明了这一点。     

A distributed pricing algorithm for achieving network‐wide proportional fairness

Proportional fairness (PF) scheduling achieves a balanced tradeoff between throughput and fairness and has attracted great attention recently. However, most previous work on PF only considers the single cell scenario. This paper focuses on the problem of achieving network‐wide PF in a generalized multiple base station multiple user network. The problem is formulated as a maximization model and solved using the dual method. By decomposing the dual objective function, we get a distributed pricing based algorithm. Optimality of this algorithm is presented. Although the algorithm is derived using fixed link rate assumption, it can still apply in the presence of time‐varying rates. The proposed algorithm is suitable for distributed systems in the sense that it does not need any inter base station communication at all. Simulations illustrate that the proposed distributed network‐wide PF scheduling algorithm achieves almost the same performance as the centralized one. Compared with traditional local PF (LPF) scheduling, the network‐wide PF scheduling achieves higher throughput, lower throughput oscillation, and greater fairness. Copyright © 2010 John Wiley & Sons, Ltd.     

传感器网络中基于事件信息量的公平性控制

在分析无线传感器网络现有公平性控制方法的基础上,依照新的公平性控制的基本原则实施带宽分配,即事件信息量是节点传输的有效信息量,公平性带宽分配是按事件信息量的比例来分配,如何计算带宽竞争节点所传的事件信息量是实现该基本原则的关键.针对事件信息均匀分布的情况,提出了以事件信息量为基础的公平性控制(EFFRC,event faith based fair rate control)算法,该算法将事件信息量的计算转换为事件区域大小的计算,并通过区域细分,将任意形状的事件区域大小的计算转换为若干四边形区域大小的求和,从而达到信息量计算的目的.实验表明,EFFRC算法能够有效计算事件信息量,实现公平的带宽分配.     

Evaluation of congestion control protocols for ABR traffic over ATM networks

Congestion control is very important for effective and stable operation of ATM (Asynchronous Transfer Mode) networks. Owing to the bursty and unpredictable characteristic of data network traffic, its congestion control is particularly a challenge for network researchers and designers. The ATM Forum has recently adopted rate‐based congestion control for ABR (Available Bit‐Rate) traffic which is the service class defined for data network applications. However, there is a number of congestion control schemes prevalent. ATM Forum has decided not to specify switch behaviour for ABR traffic; this has further introduced additional ambiguity. Consequently, an evaluation and comparison of the existing protocols would provide valuable guidance for network designers and engineers; it would also give insight for researchers to explore the essence of different congestion control schemes. In the first part of this paper, we investigate the effectiveness of ABR congestion control in the presence of bursty source traffic and the relationship between the burst time scale and the ABR control time scale. Two ABR congestion control schemes, the ABR Explicit Forward Congestion Indication (EFCI) and ABR Congestion Indication (CI) schemes, are compared with Unspecified Bit Rate (UBR) transport which makes no effort to control congestion. Traffic sources of various burst lengths of 100, 1000, 10000, and an equal mix of 100 and 10000 ATM cells are used in simulations. It is found that ABR congestion control schemes effectively control low frequency, medium to long‐term traffic load transients. This is further supported by the result of integrating TCP over ATM congestion control schemes included in the paper. ABR control schemes do not control high frequency, short‐term load transients well, but ABR control is not necessary in such cases since short‐term transients do not require a large amount of buffering. In the second part of this paper, we evaluate and compare six rate‐based congestion control protocols including Scheme I: EFCI, Scheme II: EFCI with separate RM queues, Scheme III: CI, Scheme IV: CI with separate RM queues, Scheme V: the CAPC2 ER (Explicit Rate), and Scheme VI: the EFCI with utilization‐based congestion indication. Each scheme is simulated and compared in the LAN, WAN, and GFC (General Fairness Configuration) environments specified by the ATM Forum. Effects of varying VC (Virtual Circuits) number and changing endsystem–switch distance has been investigated. Their fairness is also compared using the GFC configuration. We have found that ER control scheme performs significantly better than the other five binary control schemes by its faster response to congestion, smoother regulation of bit‐rates, lower queueing delay, shorter buffer queue length, and fairness. Among the other five schemes, the CI scheme performs better than the EFCI scheme. Providing separate RM queues has significantly improved the EFCI scheme in the WAN environment, but has little effect on the CI scheme. Link utilization‐based congestion detection has suffered from either low utilization or an excess cell loss which is unacceptable in most data applications. Copyright © 2000 John Wiley & Sons, Ltd.     

一种改进的ABR流量控制算法

为提高ATM网络流量管理性能,在随动控制结构上,进一步考虑时延因素的影响,提出了一种基于离散模型的改进的ABR流量控制算法。给出了保证时滞系统闭环稳定的参数选择方法,实现了拥塞避免和可用带宽的动态公平分配,保证了服务质量。仿真结果进一步验证了理论的正确性和可行性。     

信道公平分配的局部拥塞控制算法

提出基于信道公平分配的局部拥塞控制算法FCA(fair channel allocation),在缓解局部拥塞的同时增强信道分配的公平性。为减少获取邻居节点实时缓存信息的通信开销和提高以单一节点缓存是否溢出为检测模型的准确性,FCA采用以节点实时缓存长度预测为基础的邻居节点缓存总长度和分组平均传输延迟作为检测指标的拥塞检测模型。为避免使用独立拥塞通告消息增加信道负载,FCA采用在ACK控制帧中增加一个节点地址位携带拥塞信息。在去拥塞阶段,FCA采用基于实时缓存长度和队列优先权值的信道分配机制保证公平传输和防止部分节点因缓存增速过快导致溢出分组丢失。实验结果表明,FCA在碰撞次数、分组传递率、吞吐量和公平性等方面相比802.11、CODA和PCCP具有显著优势。     

ATM网络基于EFCI机制的拥塞控制的缓存性能

本文根据文献「１」中给出的ＡＴＭ网络拥塞控制模型,对一类简单控制方案的缓存性能了深入的分析,得到了更为精确的缓存空间和阈值,同时讨论了多种业务在网络中共存的情况,并根据ＥＦＣＩ的拥塞检测机制,提出了一种新的控制策略。仿真结果表明了分析的正确性。     

Characteristics of ABR explicit rate control algorithms in WAN environments and an ABR control algorithm suitable for public networks

This paper investigates the characteristics of available bit rate (ABR) explicit rate control algorithms in wide area network (WAN) environments. An ABR service is expected to make more effective bandwidth utilization possible through closed loop congestion control, and several control algorithms have been proposed. However, in WAN environments a long propagation control delay will affect the effectiveness of the control algorithms. Additionally, if a network supports a large number of connections, some of the algorithms may not work well. Thus we have categorized the control algorithms according to their purpose and mechanism and have evaluated their characteristics by simulation in WAN environments from the viewpoint of throughput, robustness, quickness, stability and fairness. Based on this analysis, we have developed an ABR control algorithm suitable for public networks. © 1998 John Wiley & Sons, Ltd.     

The DDTCI switch algorithm for ABR traffic control in ATM networks

For the issue of flow control for Available Bit Rate (ABR) traffic in ATM network,a new improved Explicit Rate (ER) algorithm named Dynamic Double Threshold Congestion Indication (DDTCI) algorithm is presented based on the Explicit Forward Congestion Indication (EFCI) Current Cell Rate (CCR) algorithm and Relative Rate (RR) algorithm. Different from the early ER algorithm, both the high-level and the low-level threshold is dynamically changing according to the state of the bottleneck node. We determinate the congestion state with the information of the two dynamic threshold, and control the cell rate of the source by feed back mechanism. Except for the well performance in both link utilization and fairness in distribution of available bandwidth, the improved algorithm can alleviate the fluctuation of sending rate dramatically. The mechanism is modeled by a fluid model, and the useful expressions are derived.Simulation results show up our conclusion.     

混合网络下的TCP拥塞控制跨层优化算法

针对混合网络中并行链路间TCP流的不公平性,提出一种新的算法.此算法利用跨层设计的思想,以传输层的数据重传率为参数来调整TCP流不公平性,也就是说MAC层上的竞争窗口将根据重传率的动态变化而改变,其目的在于抑制并行链路TCP流接入信道能力的不公平性.并且用仿真工具NS2进行仿真的结果表明,采用改进算法后的网络公平性指数比未改进前提高了17.9％.该算法能明显改善并行链路间TCP流的不公平性.     

Multipath congestion control algorithm based on link capacity

Factors such as link differences and TCP friendliness constraints lead to the problem of unfair bandwidth allocation when the TCP congestion control mechanism was applied directly to multi-path transmission.To address the problem,it was proposed that a multipath congestion control algorithm was based on link capacity.The proposed algorithm which was based on the concept of feedback regulation achieved multipath joint congestion control by establishing the M/M/1 cache queue model to adjust the throughput rate of senders.Experimental results show the proposed algorithm can improve the multipath transmission bandwidth utilization and the multipath congestion control algorithm responsiveness,and ensure the fairness of multipath transmission.     

A buffer management algorithm for improving up/down transmission congestion protocol fairness in IEEE 802.11 wireless local area networks

The fair allocation of the resources is an important issue in wireless local area network (WLAN) because all wireless nodes compete for the same wireless radio channel. When uplink and downlink transmission congestion protocol (TCP) flows coexist in WLAN, the network service is biased toward the uplink TCP flows, and the downlink TCP flows tend to starve. In this article, we investigate the special up/down TCP unfairness problem and point out that the direct cause is the uplink acknowledgement (ACK) packets occupy most buffer space of access point. We thus propose a buffer management algorithm to ensure the fairness among uplink and downlink TCP flows. In order to limit the greedy behavior of ACK packets, the proposed algorithm adjusts the maximum size of buffer allocated for the ACK packets. Analysis and simulation results show that the proposed solution not only provides the fairness but also achieves 10–20% lower queue delay and higher network goodput than the other solutions. Copyright © 2012 John Wiley & Sons, Ltd.     

按队长周期性设置EFCI的ABR流量控制算法

本文提出了一种新的基于EFCI的ABR流量控制算法,它的基本思想是扩展EFCI的功能,使其不仅反映网络阻塞状况,而且还反映网络排队状况,在交换机中通过周期性设置EFCI来传递网络的排队信息。仿真结果表明,本文提出的算法比基本EFCI算法具有更好的控制行为,减小了ACR和排队长度的振荡幅度,提高了链路利用率,并具有较高的性能价格比。