CAREER: Flexible Strategies for Internet Content Distribution

内容分发新技术的出现，包括内容交付网络（cdn）、终端系统多播、分布式内容交换和应用级任意播送，正在从根本上改变数字内容的消费者和生产者之间的关系。传统的内容交付方法基于从客户机到单一源服务器的点对点连接，而这些内容分发的新机制从根本上破坏了该模型中固有的假设。例如，cdn将客户端重定向到许多等效的副本服务器，而终端系统多播则更进一步，通过要求希望访问内容的每个参与者也提供内容来模糊客户端和服务器之间的区别。为了说明这一点，请考虑一个访问图，它绘制了在某个时刻通过网络提供流行文档的TCP连接流。直到最近，这张图可以很容易地被描述为形成一个中心辐状拓扑，中心位于原始服务器；现在，除了cdn内部的网络工程师之外，人们对其复杂的结构知之甚少。总的来说，研究人员的兴趣在于描述新的和日益分散的内容传递机制对网络流量、资源管理和网络协议设计的影响。在研究人员职业发展计划的研究部分，他专注于解决分布式内容交付机制对可靠传输协议所带来的挑战和机遇的策略。特别是，数字内容的消费者和生产者之间复杂的一对多和多对多关系将给TCP等传输协议带来压力，因为这些协议的设计不是为了适应当用户有多种服务选择时将发生的流动交互。研究人员认为，轻量级可靠的传输服务设计为最大的灵活性，可以容纳连接抢占，连接挂起，连接迁移和连接聚合。虽然这些考虑是基本的，但由于令人生畏的技术障碍、复杂性和缺乏驱动需求，它们尚未在TCP上下文中得到仔细研究。研究人员带来了新的技术来解决这个问题，因为提出的工作利用了他在可靠多播[11]和并行[10]从多个镜像站点下载数字内容领域应用的快速纠错编码技术的经验。在考虑的一些设置中，例如动态服务器选择和重定向，所提出的技术提供的灵活性可以被认为是性能优化，但在其他设置中，例如为终端系统多播提供可靠性，研究人员认为所提出的灵活服务对于提供高性能至关重要。研究人员职业发展计划的教育方面侧重于提高本科和研究生在其部门的经验，并为波士顿地区的工业和机构间网络研究合作建立更坚实的基础。拟议的活动围绕正在进行的项目，以促进大学生参与网络研究；加强本系的网络课程；并鼓励学生参与大学以外的计算机科学社区，无论是在社区外展项目中做志愿者，还是加入当地的计算机科学家组织。研究人员积极参与的一项令人兴奋的倡议将有助于实现这些目标，那就是在波士顿大学建立一个网络研究中心。

The emergence of new technologies for content distribution including content delivery networks (CDNs, end system multicast, distributed content exchange and application-level anycast are fundamentally changing the relationships between consumers and producers of digital content. Whereas traditional approaches to content delivery are predicated on point-to-point connections from a client to a single origin server, these new mechanisms for content distribution fundamentally undermine the assumptions inherent in that model. For example, CDNs redirect clients to a number of equivalent replica servers, while end system multicast goes further and blurs the distinction between client and server by requiring that every participant who wishes to access content serve content as well. To illustrate this point, consider the access graph plotting the flow of TCP connections serving a popular document through the network at an instant in time. Until very recently, this graph could easily be characterized as forming a hub-and-spoke topology with the hub at the origin server; now its complex structure is little known except perhaps to network engineers within the CDNs themselves. Broadly, the researcher's interests lie in characterizing the impact that new and increasingly distributed content delivery mechanisms will have on network traffic, resource management and the design of network protocols. In the research component of the researcher's career development program, he focuses on strategies for addressing the challenges and opportunities that distributed content delivery mechanisms will place on reliable transport protocols. In particular, the complex one-to-many and many-to-many relationships between consumers and producers of digital content will place strain on transport protocols such as TCP, as those protocols are not designed to accomodate the fluid interactions which will take place when users have a multiplicity of service options. The researcher argues for lightweight reliable transport services designed for maximum flexibility which can accomodate connection preemption, connection suspension, connection migration and connection aggregation. While these considerations are fundamental , they have not been carefully studied in the context of TCP because of daunting technical hurdles, complexity, and absence of a driving need. The researcher brings new techniques to bear on the problem, as the proposed work leverages his experience with fast forward error correcting coding techniques which he has applied in the domain of reliable multicast [11] and downloading digital content from multiple mirror sites in parallel [10]. In some of the settings considered, such as dynamic server selection and redirection, the flexibility which the proposed techniques afford can be considered to be a performance optimization, but in other settings, such as providing reliability for end system multicast, the researcher argues that the flexible services proposed are essential to delivering high performance. The proposed educational aspect of the researcher's career development program focuses on enhancing the undergraduate and graduate student experience in his department and building a stronger basis for industrial and inter-institutional networking research collaborations in the Boston area. Proposed activities center around ongoing projects to promote undergraduate involvement in networking research; to enhance the department's networking curriculum; and to encourage students to participate in the computer science community outside of the university, whether by volunteering at a community outreach program or by becoming involved in local organizations of computer scientists. An exciting initiative which the researcher is e actively involved in and which will help achieve these goals is the institution of a center for networking research at Boston University.