【作者】 高文娟；

【导师】 刘国柱；

【作者基本信息】 青岛科技大学 ， 计算机软件与理论， 2011， 硕士

【摘要】 Internet的迅猛发展和普及为流媒体业务发展提供了强大的市场动力。流媒体技术广泛用于多媒体新闻发布、网络广告、在线直播、电子商务、远程教育、实时视频会议等互联网信息服务的方方面面。它结束了传统Internet只能显示文字和图片的时代,开创了集声音、视频、文字及图像于一体的新纪元。流媒体传输技术由于自身传输时延敏感性,半可靠性,传输速率的平稳性等特点,在实际使用中通常采用UDP/IP协议进行传输。但UDP缺乏拥塞控制机制,拥塞发生时它不会降低数据发送速率,这样会引发两种情况:其一, UDP占用的资源将远高于TCP流等响应流所占用的资源,造成了严重不公平性;其二,它将导致拥塞情况的进一步恶化,甚至引发拥塞崩溃,严重影响流媒体服务质量。因此,必须对流媒体传输引入拥塞控制机制。传统拥塞控制算法是通过丢弃数据包后,使发送端通过收到大于等于三个重复的ACK或者重传计时器超时的方式隐式的判断拥塞的发生。本文将利用Agent技术实现拥塞的检测、控制和管理,并提出一种改进的拥塞控制算法Vegas-A+。当拥塞发生时,检测拥塞Agent将实时监测网络并报告拥塞的发生,并由控制拥塞Agent根据网络拥塞情况选择合适的拥塞控制算法来缓解或消除拥塞。利用Agent之间的协作,降低丢包率,提高网络的利用率。Agent是一个具有自适应性和智能性的软件实体,能代表用户或者其它程序,以主动服务的方式完成一项任务。它具备自主性、反应性、社会性、主动性和适应性等。本文提出用检测Agent来完成报告拥塞发生的功能;控制Agent来完成减轻或消除拥塞的功能;黄页Agent来实现Agent服务公布、服务查询和服务订阅的功能。各个Agent之间相互协作形成一个多Agent系统为网络提供服务。在对Agent功能的分析和设计基础之上,利用JADE开发平台开发多Agent系统使之实现拥塞控制功能。更多还原

【Abstract】 The rapid development and popularization of Internet provide powerful market power for streaming media business development. Streaming media technology is widely used in all aspects of Internet information services, such as multimedia news release, network advertising, online live, e-commerce, distance education, real-time video conference, etc. It ends the era of traditional Internet which only displayed words and pictures, and marks an epoch in integration of voices, videos, words and pictures.Because of its transmission delay sensitivity, half reliability, the steadiness of transmission rate, streaming transmission technology adopts UDP/IP protocol for transmission. When congestion occurs, the UDP will not reduce data sending rate for lacking of congestion control mechanism, which will trigger two situations: 1) resources occupied by UDP will be far higher than that occupied by TCP flow, which will cause serious unfairness. 2) It will cause congestion conditions further deterioration, and even cause congestion collapse, which will seriously influence streaming service quality. Therefore, congestion control mechanism must be introduced in streaming transmission. The traditional congestion control algorithms judge the congestion occurrence through the following ways: when packet is discarded, sender will receive greater than or equal to three repeated ACKs, or timeout of retransmission timer. This article will use the Agent technology to realize congestion inspection, congestion control and congestion management, and also puts forward an improved congestion control algorithm Vegas-A+. The congestion inspection Agent will inspect congestion timely and report when congestion occurs. The congestion control Agent will select suitable congestion control algorithm to control congestion according to the reports from congestion inspection Agent. Using the collaboration of all agents to reduce the packet loss rate and increase network utilization.Agent is an adaptive and intelligent software entity, which can represent user or other software to finish a task in a active service mode. It is autonomy, reactive, sociality, initiative, and adaptable. In this article, inspection Agent will inspect the congestion in the network and send reports, the control Agent will reduce or remove congestion, the yellow page Agent will provide service publish, service search, service subscription. The cooperation of all agents forms a multi-agent system providing services for networks. Based on the analysis and design of all agents’functions, the multi-agent system is developed for solving the network congestion using JADE platform.更多还原