标题: | 非同步传输模式网路中拥塞状况的避免 Congestion Avoidance In ATM Networks |
作者: | 陈婉佳 Chen, Wan-Jia 罗济群 Lo, Chi-Chun 资讯管理研究所 |
关键字: | 非同步传输模式;流量管理;Asynchronous Tranfer Mode;policing function |
公开日期: | 1993 |
摘要: | 在以非同步传输模式(Asynchronous Tranfer Mode, ATM)为交换技术的网路中,如何利用拥塞控制方法以有效率且分平的方式来分配网路资源,达到在合理的成本之下满足使用者的服务品质(Quality-Of-Service)要求,是非常重要的。网路必须对使用者加以监督与控制使其在传送资料时能遵守其在进入网路时与网路所建立的使用限制。这些使用限制包括传送资料的平均速率、最高速度与最大突发量资料长度等参数。假如使用者没有服从这参数则网路必须对这些违规的传输资料加以限制。目前在ATM中所有的流量管理(policing function)方法中以隙漏水桶法(leaky bucket)为最着名。隙漏水桶法乃是执行于网路周围,但其有可能在没参考封包的重要性之下将重要的封包加以丢弃或标示。这样将会使被丢弃的重要封包重新传输以致降低网路的效率。 在本论文中,我们提出了一个新的流量管理方法,称为具有优先权(prioity)控制的一般化隙漏水桶法,来解决这一个问题。这个方法结合了传统的隙漏水桶法与优先权的控制来达到与使用者资料相关的流量控制。本方法执行于每一个虚拟连接上,并且依照封包的优先权将封包标示以达最佳的频宽利用率与限制使用者传送资料的最高速度。同时我们在使用者与网路界面上与网路中的交换节点上分别发展了模拟的模型。模拟的结果显示我们所提出的具有优先权控制的一般化隙漏水桶法是一个能有效防止网路发生拥塞状况的流量控制方法。 It is necessary that an ATM-based network be eauipped with a congestion mechanism to effectively and fairly allocate shared network resources such as transmissson bandwidth and buffer capacity in a manner that provides satisfactory quality-of-service (QOS) for all network users with acceptable implementation costs. Traffic from users may need to be monitored and enforced to cmply with traffic parameters that could be established at the time of its admission to the ATM network. These parameters may include average and peak bit rates, and maximum burst lengths. If the user dose not conform to the parameters, actions must be taken for the violated traffic. In currently proposed ATM policing functions, the leaky bucket mechanism is the most popular approach. However, it is carried out at the network edge, which opens the possibility of cells being discarded or marked without reference to the actual massage. This may lead to degradation of the network performance. In this thesis, we propose a new policing funciton, called the generalized leaky bucket leaky bucket mechanism with priority control, to solve this problem. This scheme combines the traditional with priority control to provide a service-dependent marking. The proposed scheme operates on a per virtral connection basis. It marks the cells according to their priorpity so as to achieve an optimistic bandwidth utilization and limit the peak rate at which the cells enter the network. Simulation models for both the user-network interface and the intermediate switching node are developed. Simulation results show that the generalized leaky bucket with priority control is an effective approach to prevent congestion from occurring. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#NT823396011 http://hdl.handle.net/11536/58610 |
显示于类别: | Thesis |