基于移动Agent的网络拥塞控制的设计与实现

【作者】 程杰；

【导师】 杨兴强；

【作者基本信息】 山东大学 ， 软件工程， 2005， 硕士

【摘要】 拥塞控制对网络服务质量的影响一直倍受关注,然而拥塞控制算法的分布性、网络的复杂性和对拥塞控制算法的性能要求又使拥塞控制机制的设计具有很高的难度。到目前为止,拥塞问题还没有得到很好的解决。近几年来,移动代理技术日益成熟,在许多领域开辟了新的研究空间。考虑到移动代理所具备的迁移性、低流量性以及平台无关性等特点,本系统设计旨在将该技术应用到拥塞控制研究过程中。 本设计主要实现两个功能:一是实现控制端对移动代理和拥塞数据的管理及移动代理对拥塞数据的采集。用户可通过自动或人工方式实时向网络派遣移动代理,使其从各结点检测代理采集拥塞状态数据,经过滤和计算获得各拥塞结点的拥塞状态值、地址、拥塞时间等数据最终交付控制端参与统计分析,向用户反馈网络拥塞的当前信息、历史数据以及网络平均资源利用率作为用户调整网络结构和预测拥塞的依据;二是设计并实现一种基于结点的拥塞控制机制:当分组队列占用率达到系统拥塞阈值时,该结点的检测代理读取队列中分组源地址,向源端发送拥塞抑制分组,指示源端降低数据流量,若分组队列占用率达到结点拥塞门限值,检测代理即向控制端发送拥塞报警信息以触发移动代理的自动派遣,同时向邻结点的检测代理发送拥塞通知信息,触发路由信息的变更以达到缓解拥塞的目的。 为检验应用效果,系统自行搭建模拟环境,模拟真实环境下各结点的工作过程,包括:模拟开放最短通路优先OSPF协议,各结点使用链路状态算法变更路由表;模拟各路由结点对分组的发送、转发以及接收处理过程;模拟各结点队列在分组流动过程中的动态变化。系统在模拟环境下获得了预期的实验结果。 考虑到Agents的安全性以及实用性,系统采用IBM Aglets作为移动代理平台。与传统拥塞控制相比,由于Aglet为轻量线程,只占用很少的网络资源,使系统能够以低代价获得较全面的拥塞信息,并且在网络扩展情况下具有较好的灵活性,这是传统拥塞控制不易做到的。更多还原

【Abstract】 Congestion control, which exerts profound influence on the network quality of service, always arouses great concern. However, the distribution of congestion control algorithms, the complexity of networks and functional demand make the design of congestion control algorithms quite difficult. Therefore, congestion problem hasn’t been solved so far. While during these years, mobile agent technology is maturing gradually, which provides much new research space in many fields, and attains fruitful solutions as well. Thinking of the characteristic of mobile agent such as migration、 lower flowing and the independence of the platform, this system design applies this new technology into the research of the congestion control.This system mainly implements two functions. Firstly, it provides management to the mobile agents and congestion information for the controller. In this system, users can dispatch mobile agents to the networks automatically. By this means, mobile agents will exchange information with the node-checking agents so as to fetch every node’s congestion state information, such as congestion status, address, time stamp etc to the controller as a analysis foundation. Secondly, this system proposes and realizes a kind of congestion control method, when the ratio of packets occupying the node’s queue reaches to the limit data, the node check agent will alert to the controller and adjacent nodes so as to inform controller to dispatch a new mobile agent and release congestion by updating the routing table temporarily.In order to check the application result, this system establishes a simulated experiment environment to simulate the working process of every routing node in the networks. The simulated experiment environment includes OSPF protocol, updating routing table based link state routing algorithm, packets sending, resending and receiving process among routing nodes and so on. This system acquired expected experiment result under the simulated circumstance.Thinking of the security and application of mobile agents, this system uses IBM Aglet as mobile agent platform. Compared with traditional congestion control method,aglet is based on light thread process which occupies very few resource of networks, therefore, this system can provide a way to get congestion information with low price and good mobility, which is not easy to realize by traditional means.更多还原