A Scaleable Multicast Protocol to Enable Future-Generation Large Scale Multimedia Applications

一张图片胜过千言万语，加上声音和动态可以给图片注入活力，因此，在各种多媒体应用中使用视频已成为20世纪90年代的一个重要发展。特别是，视频点播（VOD）是许多重要应用的核心技术，如数字图书馆，远程教育，电子商务，娱乐，公共信息系统等。最简单的视频传输技术采用一个专用的流为每个服务请求。显然，这种方案过于昂贵，并且已经被证明具有很小的可扩展性。为了大大降低成本，可以利用多播技术来允许多个客户端共享视频流。不幸的是，今天的多播技术是在80年代开发的，并没有针对这些应用进行优化。错过多播可能意味着下一个多播要等很长时间。这种局限性最近导致了大量的研究在应用层寻找补救措施。然而，应用层的解决方案不能解决所有的缺点，特别是由太多的多播引起的流量拥塞。事实上，这个建议是由研究者在他的最后一个NSF项目（从1998年到2000年）中所做的应用级工作所激发的。该项目的成果虽然很有意义，但受到标准组播局限性的制约。最小化多播频率对于任何基于多播的应用都是至关重要的，特别是那些运行在公共网络（如Internet）上的应用。实现这一目标需要组播概念的根本改变。本发明提出使多播树能够将整个视频传送到可能在不同时间订阅多播的所有接收器。这种新的能力将大大减少所需的多播数量，从而降低网络资源需求。乍一看，这似乎是一个不可能完成的任务。但相反，这可以通过允许组播树上的路由器拦截并缓存经过的视频流来实现。数据可以被中继到后续的订户以进一步扩展多播树。在这个项目中，研究者提出了一套technologesto使这样的环境实际的下一代大规模的多媒体applications.To评估所提出的想法的潜力，研究者设计了一个初始版本的hisCaching组播协议（CMP）。初步研究表明，这种方法有可能彻底改变多媒体信息的传播方式。这种方案比应用级解决方案更易于扩展，成本更低。然而，新的通信范式要求在网络层面进行新的研究。在这个项目中，研究者建议研究诸如缓存组织、缓存替换策略、多播路由算法、拥塞控制、客户端和服务器协议等问题。此外，他将实现一个原型，由具有CMP能力的路由器组成，符合CMP标准的服务器（源）和符合CMP标准的客户端本项目的意义在于推进多播技术的发展，使多媒体应用能够大规模部署。尽管信息技术领域取得了许多重大进展，但没有一个能像多媒体信息系统那样对普通公民的日常生活产生如此巨大和直接的影响。因此，这项研究的好处将惠及社会上的许多人。在教育方面，该项目将帮助支持三名博士生。调查员有一个良好的记录，使用NSF的项目，以培训学生的教学生涯。这些学生毕业后，他们可以帮助传播从这个项目开发的CMP专业知识到他们的新机构。其他参加我们高级数据库课程的研究生也可以通过在CMP测试平台上试验各种新的多播应用程序从这项工作中受益。为了接触社区成员，将在调查员的研究小组网站上传播这项研究的材料。

A picture is worth a thousand words, and the addition of sound and motion can breathe life into a picture.As a result, the use of video in all kinds of multimedia applications has become an important developmentin the 1990s. In particular, Video on demand (VOD) is a core technology for many important applicationssuch as digital libraries, distance learning, electronic commerce, entertainment, public informationsystems, etc.The simplest video delivery technique employs a dedicated stream for each service request. Obviously,this scheme is too expensive and has been shown to have little scalability. To vastly reduce this cost, onecan leverage multicast technology to allow multiple clients to share a video stream. Unfortunately, today'smulticast technology was developed in the 80's, and was not optimized for such applications. Missing amulticast could mean a long wait until the next multicast. This limitation has recently led to a large bodyof research looking for remedies at the application level.Application-level solutions, however, cannot address all the drawbacks, particularly traffic congestioncaused by too many multicasts. In fact, this proposal is motivated by application-level work done bythe investigator in his last NSF project (from 1998 to 2000). The achievements of that project, thoughsignificant, were constrained by the limitation of standard multicast. Minimizing the multicast frequencyis crucial for any multicast-based applications, particularly those running on a public network such as theInternet. Attaining this goal requires a fundamental change in the multicast concept. The investigatorproposes enabling the multicast tree to deliver the entire video to all the receivers who may subscribe tothe multicast at different times. This new capability would significantly reduce the number of multicastsnecessary, and therefore lower the network resource requirements. At first sight, this seems like a missionimpossible. But on the contrary, this can be achieved by allowing the routers on the multicast tree tointercept and cache a video stream passing through. The data can be relayed to subsequent subscribers tofurther extend the multicast tree. In this project, the investigator proposes to develop a suite of techniquesto make such an environment practical for future-generation large-scale multimedia applications.To assess the potential of the proposed idea, the investigator has designed an initial version of hisCaching Multicast Protocol (CMP). The preliminary study indicates that this approach has the potentialto revolutionize the way in which multimedia information is disseminated. This scheme is much morescalable and less expensive than application-level solutions. The new communication paradigm, however,demands new research at the network level. In this project, the investigator proposes to study issues suchas cache organization, cache replacement policies, multicast routing algorithms, congestion control, clientand server protocols, etc. In addition, he will implement a prototype, consisting of CMP-capable routers,CMP-compliant servers (sources) and CMP-compliant clients (destinations) to examine the practicality ofthe proposed techniques.The significance of this project is in advancing multicast technology to enable large-scale deploymentof multimedia applications. Although many great advances have been made in the field of informationtechnology, none have had as great and direct an impact on the daily lives of ordinary citizens as multime-diainformation systems. As such, the benefits of this research will reach many people in society. In termsof education, this project will help to support three doctoral students. The investigator has a good recordof using NSF projects to train students for teaching careers. After these students graduate, they can helpto spread the CMP expertise developed from this project to their new institutions. Other graduate studentstaking our advanced databases course can also benefit from this work by experimenting with various newmulticast applications on the CMP testbed. To reach out to members of communities, materials resultingfrom this research will be disseminated on the investigator's research group website.