CAREER: Flexible, Large-Scale Best-Effort Quality of Service in the Internet

对于它的大多数用户来说，因特网仍然是一个尽力而为的网络，并且没有提供直接的手段来满足应用程序的特定网络服务质量（QoS）要求，例如固定带宽或传播延迟和损失率的限制。大多数先前解决网络qosco功能改进的工作集中在需要结合资源保留、准入控制以及对协议栈的网络和传输层进行大规模修改的机制和技术上。这些机制和技术很难在实践中部署，因为a)它们需要在已经运行的协议栈的较低层中进行更改和新的标准，b)它们限制竞争会话对基本网络资源的访问。最近，作为一种替代方案，研究人员和网络从业者利用在网络应用层内实现的分布式机制来补偿底层尽力而为的网络基础设施的QoS限制。这些机制提供了诸如替代路径路由、网络内部数据转码、内容复制和缓存等服务，以提高会话质量。实现这些分布式机制的网络点之间的数据和状态信息通信是在网络覆盖层上执行的：虚拟网络通过穿越底层网络的隧道传输直接将这些点彼此连接起来。本提案中描述的研究开发并分析了一种用于广域互联网的尽力而为的QoS服务。该服务将应用程序使用的过程自动化，以利用这些分布式应用层机制来提高网络的感知质量和功能。应用程序通过在网络端点上放置特定的QoS请求来启动服务。然后，服务将尽最大努力定位和实例化必要的分布式机制，以满足QoS需求。该服务是尽力而为的，因为它没有限制或拒绝其他会话访问网络资源的保留或许可控制阶段。因此，不能保证满足QoS要求，也不能保证一旦满足，在会话的剩余时间内也能满足该要求。唯一的保证是，只要可以找到应用层资源并有效地应用于满足需求，那么服务就会这样做。本提案中的工作将在三个广泛的领域评估该服务：(i)定位可用应用层资源的技术，（ii）这些资源的协调选择，以及（iii）控制竞争应用程序如何共享这些资源。我们的评估主要是通过对一般服务的数学分析和模拟来完成的。然而，我们也通过将分析扩展到两个特定的应用程序以及为实验目的开发和使用测试平台来演示该服务的实用性。研究人员的教学工作集中在网络研究的分析和实验方面的相互交织。为此，他建议开发网络课程，(i)教授网络系统建模和性能评估的基本方法，（ii）在互联网2上开发一个广域教室实验室，供世界各地的学生使用，以实施广域实验，（iii）教学生如何将实验和理论方法整合到网络问题中。

For the majority of its users, the Internet remains a best-effort network and provides no direct means formeeting specific network Quality of Service (QoS) requirements of applications, such as fixed bandwidthrates or bounds on propagation delay and loss rates. Most previous work that addressed improving QoScapabilities of networks focused on mechanisms and techniques that require a combination of resourcereservation, admission control, and wide-scale modifications to the network and transport layers of theprotocol stack. These mechanisms and techniques are difficult to deploy in practice because a) they requirechanges and new standards within already operational lower layers of the protocol stack and b) they restrictcompeting sessions' access to basic network resources. Recently, as an alternative, researchers and network practitioners have utilized distributed mechanismsimplemented within the network's application layer to compensate for the QoS limitations of the underly-ingbest-effort network infrastructure. These mechanisms provide services such as alternate path routing,network-internal transcoding of data, content replication and caching that improve session quality. Communication of both data and state information between the network points that implement these distributed mechanisms is performed upon network overlays: virtual networks that directly connect these points to one another by tunneling transmissions across the underlying network. The research described in this proposal develops and analyzes a Best-Effort QoS service for the wide-areaInternet. This service automates the procedure used by applications to draw upon these distributedapplication layer mechanisms to improve the perceived quality and capabilities of the network. An application initiates the service by placing a specific QoS request at a network endpoint. A best effort is then made by the service to locate and instantiate the necessary distributed mechanisms to meet the QoS requirement. The service is best effort in that there is no reservation or admission control phase that restricts or denies other sessions' access to network resources. Hence, there is no guarantee that the QoS requirement will be met, nor is there a guarantee that once met, the requirement will be satisfied for the remainder of the session. The only guarantee is that as long as application layer resources can be located and effectively applied to meet the requirement, then the service will do so. The work in this proposal will evaluate this service in three broad areas: (i) techniques for locatingavailable application layer resources, (ii) coordinated selection of these resources, and (iii) controlling howcompeting applications share these resources. Our evaluation is performed mainly via mathematical analysisand simulation upon a generic service. However, we also demonstrate the practicality of the service byextending the analysis to two specific applications as well as developing and using a testbed for experimentalpurposes. The researcher's teaching efforts focus on the intertwining of analytical and experimental aspects of networking research. To this end, he proposes to develop courses in networking that (i) teach fundamental approaches to modeling and performance evaluation of networking systems, (ii) develop a wide-area classroom laboratory atop the Internet2 that can be used by students across the world to implement wide-area experiments, and (iii) teach students how to integrate experimental and theoretical approaches to networking issues.