ABR业务特性及业务量管理方法

由ＡＴＭ Ｆｏｒｕｍ提出的ＡＢＲ业务近来颇受各方关注，本文给出了ＡＢＲ业务的背景，ＡＢＲ业务的特点及其流量控制方法，并对在实现ＡＢＲ业务过程中可能碰到的问题进行了讨论。     

ABR业务流量控制中的是速率反馈

ＡＢＲ（Ａｖａｉｌａｂｌｅ Ｂｉｔ Ｒａｔｅ）业务可以提高ＡＴＭ网络的利用率，能让用户ＬＡＮ通过广域网进行高吞吐量、低丢失率的互通。可以预计，未来ＡＴＭ网上的数据业务将主要用ＡＢＲ连接来传输。ＡＢＲ业务中的首要问题是流量控制。文章在比较了几种流量控制方案后，认为显速率反馈是ＡＢＲ业务流及拥塞控制的一个有效方法，是完善ＡＢＲ业务的一个重要手段，并对显速率算法作了进一步研究。     

VBR背景业务下的ABR拥塞特性

ＡＢＲ业务的拥塞控制方案是当前ＡＴＭ研究方面的热点,本文首先分析了存在ＶＢＲ背景业务时,ＡＢＲ拥塞控制方案的动态特性,然后将此分析模型用于研究明确速率反馈交换机的排队性能,并研究了ＴＣＰｏｖｅｒＡＢＲ的拥塞特性。     

ATM网络中ABR业务的开环控制机制

ＡＴＭ网络中ＡＢＲ业务的流量控制是ＡＴＭ论坛的流量管理规范（ＴＭ４．０）中没有完全解决的问题,ＡＢＲ基于速率的闭环控制方案在最大－最小准则下获得了一定进展。但在拥塞发生在信源外或对突发性业务进行控制的情况下,添加开环控制的ＡＢＲ拥塞控制可以获得比闭环控制更佳的作用。研究了ＡＢＲ的开环控制方案,早期的ＵＩＬＩ机制本身存在在一定的问题,在交换机处采用基于计数的ＵＩＬＩ机制能够取得较好的效果。     

基于ATM的无源光网络媒质接入控制协议的设计

针对基于ＡＴＭ的无源光网络（ＡＴＭ－ＰＯＮ）设计了一种媒质接入控制（ＭＡＣ）协议。该协议的设计遵照ＩＴＵ－Ｔ有关ＡＴＭ－ＰＯＮ的建议Ｇ．９８３．１（１９９８年１０月）中所定义的帧结构。该协议能够支持ＣＢＲ／ＶＢＲ、ＡＢＲ和ＵＢＲ等多种业务,并能够保证用户公平地接入和充分地利用网络的资源。其中ＣＢＲ／ＶＢＲ业务的优先级最高,同时也确保ＡＢＲ业务至少能以最小信元通信。系统的剩余带宽资源被分配给ＵＢＲ业     

ATM网中ABR业务的缓存性能

ＡＢＲ（ＡｖａｉｌａｂｌｅＢｉｔＲａｔｅ）业务是ＡＴＭ网为了充分利用网络的剩余带宽而提供的一种新型数据业务。ＡＢＲ业务采用反馈式流量控制，因而交换结点的缓存成了关系业务服务质量的关键问题。本文通过对一个简单ＡＢＲ流量控制模型的分析得出：适当地设置交换结点的缓存大小和门限值，可以保证该结点处无信元丢失，同时保证输出线路容量得到充分利用。对一个复杂模型的模拟结果表明，本文提出的缓存大小和门限值的设置方法是行之有效的。     

ATM网中的ABR业务的缓存性能

ＡＢＲ业务是ＡＴＭ网为充分利用网络的剩余带宽而提供的一种新型数据业务。ＡＢＲ业务采用反馈式流量控制，因而交换结点的缓存成了关系业务服务的关键问题。本文通过对一个简单ＡＢＲ流量控制模型分析得出；适当地设置交换结点的缓存大小和门限值，可以保证该结点处无信元丢失，同时保证输出线路容量得到充分利用。对一个复杂模型的模拟结果表明，本文提出的缓存大小和门限值的设置方法是行之有效的。     

ATM网络中ABR业务的流量控制

本文讨论了ＡＴＭ网络中ＡＢＲ业务的特性及基于ＡＢＲ业务的拥塞控制机制，了拥塞控制技术的最新发展情况，并比较了各种控制机制的优缺点。     

ABR和UBR业务模型的TCP接入分析

ＡＢＲ和ＵＢＲ业务是ＡＴＭ中新定义的业务类型，主要面向数据传输服务。ＴＣＰ是目前最为流行的数据输协议，采用基于窗口的拥塞控制机制。本文主要讨论了ＴＣＰ接入ＡＢＲ和ＵＢＲ业务时所呈观的一些特点及ＡＴＭ交换机缓存的大小对ＴＣＰ性能的影响。     

ATM网络中基于ABR业务的闭环拥塞控制

论文讨论了ＡＴＭ网络中ＡＢＲ业务的特性及基地ＡＢＲ业务的拥塞控制机制，了拥塞控制技术的最新发展情况，并比较了各种控制机制的优缺点。     

Source behavior for ATM ABR traffic management: an explanation

The available bit rate (ABR) service has been developed to support data applications over asynchronous transfer mode (ATM) networks. The network continuously monitors its traffic and provides feedback to the source end systems. This article explains the rules that the sources have to follow to achieve a fair and efficient allocation of network resources     

一种基于对策模型的ATM网络连接接纳控制策略

本文先简述了ATM网络进行连接接纳控制(Connection Admission Control:CAC)的主要方法,其中主要综述了基于动态带宽分配的CAC策略,而后从合作对策模型的角度讨论业务间共享链路资源的公平性问题,提出一种基于时延带宽积的业务收益函数形式,并通过遗传算法求解待优化的对策函数,以决定对呼叫请求的接入或拒绝。仿真结果表明此方法能够更好地保证不同带宽和服务质量要求的业务共享网络资源的公平性。     

ATM网络中面向ABR服务的一种流量控制机制

在ATM网络有效和稳定的运行过程中,拥塞控制起着重要的作用.对此,本文提出一种方法来设计基于速率的流量控制机制以便调节ABR服务并有效地控制网络拥塞.目标是在多个竞争用户间公平分配可用链路带宽、维持瓶颈结点的队列长度在希望值.该机制基于最小节拍(DR)控制并具有非常简单的结构.仿真结果表明,该控制机制是公平的并且具有快速收敛、无振荡和高链路带宽利用率的优点.     

Engineering ATM networks for congestion avoidance

With the combination of telecommunication, entertainment and computer industries, computer networking is adopting a new method called Asynchronous Transfer Mode (ATM) networking. Congestion control plays an important role in the effective and stable operation of ATM networks. Traffic management concerns with the design of a set of mechanisms which ensure that the network bandwidth, buffer and computational resources are efficiently utilized while meeting the various Quality of Service (QoS) guarantees given to sources as part of a traffic contract. In this paper, the most widely recognized congestion control schemes for ABR service are investigated. Some of these schemes show either lack of scalability or fairness while other well‐behaved schemes may require a highly complex switch algorithm that is unsuitable for implementation in cell‐switching high‐speed ATM networks. A new and improved congestion control scheme is proposed to support the best‐effort ABR traffic. This algorithm provides the congestion avoidance ability with high throughput and low delay, in addition to achieving the max–min fairness allocation. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effective control of traffic flow in ATM networks using fuzzyexplicit rate marking (FERM)

We describe the fuzzy explicit fate marking (FERM) traffic flow control algorithm for a class of best effort service, known as available bit rate (ABR), proposed by the ATM Forum. FERM is an explicit rate marking scheme in which an explicit rate is calculated at the asynchronous transfer mode (ATM) switch and sent back to the ABR traffic sources encapsulated within resource management (RM) cells. The flow rate is calculated by the fuzzy congestion control (FCC) module by monitoring the average ABR queue length and its rate of change, then by using a set of linguistic rules. We use simulation to compare the steady-state and transient performance of FERM with EPRCA (a current favourite by the ATM Forum) in the presence of high priority variable bit rate (VBR) video and constant bit rate (CBR) in both a local-area network (LAN) and a wide-area network (WAN) environment. Our experiments show that FERM exhibits a robust behavior, even under extreme network loading conditions, and ensures fair share of the bandwidth for all virtual channels (VCs) regardless of the number of hops they traverse. Additionally, FERM controls congestion substantially better than EPRCA, offers faster transient response, leads to lower end-to-end delay and better network utilization     

An empirical evaluation of virtual circuit holding time policies inIP-over-ATM networks

When carrying Internet protocol (IP) traffic over an asynchronous transfer mode (ATM) network, the ATM adaptation layer must determine how long to hold a virtual circuit opened to carry an IP datagram. We present a formal statement of the problem and carry out a detailed empirical examination of various holding time policies taking into account the issue of network pricing. We offer solutions for two natural pricing models, the first being a likely pricing model of future ATM networks, while the second is based on characteristics of current networks. For each pricing model, we study a variety of simple nonadaptive policies as well as easy to implement policies that adapt to the characteristics of the IP traffic. We simulate our policies on actual network traffic, and find that policies based on least recently used (LRU) perform well, although the best adaptive policies provide a significant improvement over LRU     

一种无线ATM网络的MAC协议

主要研究了无线ATM网络对MAC的需求，并介绍了适用于无线ATM的一种新的MAC方案。该协议支持不同类型信息传输，比如恒定比特率（CBR），可变比特率（VBR），可用比特率（ABR），未指定比特率（UBR）。另外此协议还提供了对宽带ATM主干网的无缝连接。同时也支持与ATM相关的QoS级别。对于该协议关注的各种情况的主要原理进行了讨论。     

A connection admission control scheme based on game theoretical model in ATM networks

In this paper, the main schemes of connection admission control (CAC) in ATM networks are briefly discussed especially the principle of dynamic bandwidth allocation. Then the fair share of the bandwidth among different traffic sources is analyzed based on cooperative game model. A CAC scheme is proposed using the genetic algorithm (GA) to optimize the bandwidth-delay-product formed utilization function that ensures the fair share and accuracy of accepting/rejecting the incoming calls. Simulation results show that the proposed scheme ensures fairness of the shared bandwidth to different traffic sources.     

ATM网络的链路平衡配流策略

本文提出了一种全新的流量分配策略－－链路平衡配流策略,它把平衡思想引入配流过程,利用需求与阻抗的平衡,达到网络流量的最佳分配。本文详细介绍了链路平衡配流策略的概念,还介绍了本策略的数学模型。本文的工作为配流问题的研究提供了一种新思想,新方法。     

Link Capacity Sharing between Guaranteed- and Best Effort Services on an ATM Transmission Link under GoS Constraints

While link allocation policies in multi-rate circuit switched loss models have drawn much attention in recent years, it is still an open question how to share the link capacity between service classes in a fair manner. In particular, when an ATM link is offered calls from service classes with/without strict QoS guarantees one is interested in link capacity sharing policies that maximize throughput and keep the per-class blocking probabilities under some GoS constraints. In this paper we propose a model and associated computational technique for an ATM transmission link to which CBR/VBR and ABR classes offer calls. We also propose a simple link allocation rule which takes into account blocking probability constraints for the CBR/VBR calls and a throughput constraint for the ABR calls and attempts to minimize the blocking probability of ABR calls. Numerical examples demonstrate the effectiveness of the policy and of the applied computational technique.