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

对于大多数用户来说，互联网仍然是一个尽力而为的网络，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，例如固定的带宽速率或传播延迟和丢失率的界限。以往的工作大多着眼于改善网络服务质量的机制和技术，这些机制和技术需要结合资源节约、接纳控制和对协议栈的网络层和传输层进行大规模修改。这些机制和技术在实践中很难部署，因为a)它们需要在协议栈的已经运行的较低层内改变和新的标准，以及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，研究人员和网络实践者利用网络应用层中实现的分布式机制来补偿未尽最大努力的网络基础设施的服务质量限制。这些机制提供诸如备用路径路由、数据的网络内部代码转换、内容复制和缓存等服务，以提高会话质量。在实现这些分布式机制的网络点之间的数据和状态信息的通信是在网络覆盖上执行的：网络覆盖是通过在底层网络上通过隧道传输将这些点直接彼此连接的虚拟网络。本方案中描述的研究开发和分析了广域互联网的尽力而为服务。该服务自动执行应用程序使用的过程，以利用这些分布式应用层机制来提高网络的感知质量和能力。应用通过在网络端点处放置特定的QOS请求来发起服务。然后，服务将尽最大努力定位和实例化必要的分布式机制，以满足服务质量要求。该服务是尽力而为的，因为没有限制或拒绝其他会话访问网络资源的预留或准入控制阶段。因此，不能保证将满足服务质量要求，也不能保证一旦满足，在会话的剩余时间内将满足该要求。唯一的保证是，只要能够找到并有效地应用应用层资源来满足需求，那么服务就会这样做。本提案中的工作将在三个大的领域对这项服务进行评估：(I)定位可用的应用层资源的技术，(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。我们的评估主要通过数学分析和对通用服务的模拟来执行。然而，我们还通过将分析扩展到两个特定的应用程序以及开发和使用用于实验目的的测试床来证明该服务的实用性。研究人员的教学努力侧重于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，这些课程(I)教授网络系统建模和性能评估的基本方法，(Ii)在Internet2上开发一个广域课堂实验室，供世界各地的学生用于实施广域实验，以及(Iii)教学生如何整合网络问题的实验和理论方法。

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.