Server Selection in Emerging Information Delivery Environments

现在，将信息从内容服务器及时传送到客户端显然是泛在网络的主要角色之一。随着通过网络寻找信息的人数的增加，信息传递服务的可扩展性成为一个重要的问题。服务器复制是服务提供商用来满足日益增长的信息需求的一种常用技术。然而，有效的服务器复制需要适当的服务器选择方法，如果没有这种方法，复制的全部好处将无法实现。糟糕的服务器选择通常会导致一系列相关的系统性能影响：客户端感知到的性能下降，可能由于服务器过载而拒绝请求，其他访问所选服务器的客户端观察到的性能下降，以及由于负载不平衡导致的热点导致其他网络连接观察到的性能下降。我们提出了一个研究计划，从服务和网络的当前状态开始，但主要关注未来的网络和服务环境，提供对服务器选择问题的系统调查。广域联网能力和信息服务性质的不断演变和创新将导致服务器选择问题更加复杂，影响选择的性能和政策问题也更加多样。这项工作将考虑五种类型的服务：传统的Web和FTP服务、多播服务、多媒体流服务、多源服务和中介服务。研究人员将这些视为不同的服务维度，它们可能以某种组合出现在已部署的服务中，并探索了为每个维度选择服务器的挑战。研究人员还将考虑如何使用新的网络基础设施能力(从支持某种形式的区分服务到更广泛的主动联网建议)来增强和支持服务器选择功能。研究的主要贡献将是：1.开发和评估利用网络支持来辅助服务器选择功能的技术。组播服务器选择问题的表征、机制、策略及其评价。在当前和未来的网络环境中选择流媒体视频服务器的技术。使用交互式多媒体自动点唱机(IMJ)(http://imj.gatech.edu))和研究人员先前开发的组播网络服务器来为建议的组播和多媒体流服务器的服务器选择协议提供概念证明。5.两种新的服务模式(多源服务和中介服务)的进一步定性和服务器选择建议。一个可重用的实验平台，用于试验服务器选择方案。所提出的工作将超越当今环境中不需要复杂的服务器选择机制；目前，用于将客户端分配到服务器的循环或其他简单技术就足够了。然而，这种简单和特别的技术在上述趋势将导致的更丰富的环境中不会很好地工作。该工作考虑了在未来的网络服务环境中实现服务器选择的体系结构、机制和策略。研究人员认为，他们的研究实际上将起到促进作用，因为如果没有一个可行的服务器选择系统，未来的好处就无法实现。

Timely delivery of information from content servers to clients is now clearly one of the primary roles of ubiquitous networking. As the number of people seeking information through networks increases, scalability of information delivery services becomes an important issue. Server replication is one common technique used by service providers to accommodate the increasing information demands. Effective server replication, however, demands appropriate server selection approaches, without which the full benefits of replication will not be realized. Poor server selection often leads to an array of associated system performance implications: degraded performance as perceived by the client, possible rejection of the request due to server overload, degraded performance observed by other clients accessing the selected server, and poor performance observed by other network connections due to hot spots resulting from unbalanced load.The focus of this proposal is on the design and evaluation of server selection approaches specifically in the context of wide-area server replication. We propose a research program that provides a systematic investigation of the server selection problem starting with the current state of services and networks but mostly concerned with future networking and service environments. Continuous evolution and innovation in the capabilities of wide-area networking and the nature of information services will result in a much more complex server selection problem with a wider diversity of performance and policy concerns that affect selection. The work will consider five types of service: traditional Web and FTP services, multicast services, multimedia streamed services, multi-source services and brokered services. The researchers consider these as different service dimensions that may be present in some combination in deployed services and explore the challenges in server selection for each dimension. The researchers will also consider how new network infrastructure capabilities (ranging from support for some form of differentiated service to the more far-reaching Active Networking proposals) can be used to enhance and support the server selection function.The main contributions of the research will be:1. Development and evaluation of techniques for the use of network support to aid the server selection function.2. Characterization, mechanisms, policies and their evaluation for the multicast server selection problem.3. Techniques for streamed video server selection in current and future network environments.4. The use of the Interactive Multimedia Jukebox (IMJ) (http://imj.gatech.edu) and the researchers' previously developed multicast web server to provide proof of concept for the proposed server selection protocols for multicast and multimedia stream servers. 5. Further characterization and server selection proposals for two novel service paradigms (multiple-source and brokered services).6. A reusable experimental platform for experimenting with server selection proposals.The proposed work will go beyond server selection mechanisms in today's environment which do not need to be complex; round-robin or other simple techniques for allocating clients to servers are currently adequate. Such simple and ad-hoc techniques will not, however, work well in the richer environment that the trends above will lead to. The work considers the architecture, mechanisms and policies by which server selection may be accomplished in this future networked service environment. The researchers believe that their research will, in fact, play an enabling role, since this future's benefits cannot be realized without a workable system for server selection.