WebTP: A User-Centered Web Transfer Protocol

WebTP：以用户为中心的 Web 传输协议

• 批准号: 9872764
• 负责人: Jean Walrand
• 金额: $ 115.04万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-10-01 至 2002-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9872764&HistoricalAwards=false
• 关键词: WebTP; User; Centered; Web; Transfer

The World Wide Web is now a critical communication infrastructure forsociety. However, the foundations on which the Web is built are largely adhoc and haphazard, with a protocol framework consisting of the hypertexttransport protocol (HTTP) layered on top of the Internet's universalreliable delivery protocol-the transmission control protocol (TCP).Consequently, the performance of HTTP over TCP suffers from a number ofdeficiencies that are all rooted in the fact that TCP's byte-streamsemantics are often at odds with user goals and the performancecapabilities of end clients and servers.Several ad hoc remedies have been proposed earlier to compensate for thesedeficiencies, e.g. parallel connections, persistent connections, and ACKpacing. However, all these solutions are overly constrained by thepresumption of backward compatibility. We believe that the time has come toadopt a holistic and integrated approach embodied in a new transportprotocol tailored specifically for the Web. Herein, we propose a set ofresearch tasks to study, design, implement, test and evaluate our new ``WebTransport Protocol" or WebTP.Our approach is based on a conceptual model of user validation, applicationsemantics, network and client states, and a flexible protocol that reflectsthis syntax and semantics. The conceptual model emphasizes the interactionbetween document structure, network state, and user preferences. Ourresearch prototype will leverage the well-established and highly successfulcongestion control framework of TCP and vastly improve upon the existingWebprotocols by bringing user requirements into the design loop. To do so, wewill apply the principles of Application Level Framing (ALF) to the designof WebTP. ALF says that to optimize communication paths within theapplication and across the network, an application's semantics (i.e. itsuser requirements) should be explicitly reflected in the design of itsnetwork protocol. Although ALF has been adopted in modern protocols likethe Real-time transport protocol (RTP), paradoxically it has not beensystematically applied to previously existing applications like the Web.We will study the following questions:* How do we best structure the ALF-based Web protocol in terms ofcongestion control algorithms, loss recovery schemes, packet framingmethodology, header formats, toolkit APIs, and so forth? How do thesedesign decisions impact network performance, user satisfaction, protocolcomplexity, and server load?* How then does the client elicit user preferences in the least obtrusivefashion?* How does the receiver (client) learn of the content structure of aserver's Web data and combine that structure with its estimate of networkstate and user preferences to control selective transmission via WebTP?* How should functionality and state information be distributed among thesource (server or proxy), client, and user and what are the design andperformance tradeoffs? How does WebTP scale with increased speed and fasterclients?Our approach to these questions draws upon network engineering andcommunication theory, signal processing and stochastic control. We willuse existing network emulation infrastructure from the the INDEX Project tocomprehensively test and evaluate WebTP. This project holds the potentialto dramatically impact the way we think about Web transport and willfurther contribute a design methodology, an actual protocol architecture,and performance analysis and results. We believe that our versions of WebTPwill demonstrate dramatic improvements and pave the way for furtherdevelopments.

万维网现在是社会重要的通信基础设施。然而，构建Web的基础在很大程度上是临时的和随意的，协议框架由超文本传输协议（HTTP）组成，该协议框架位于Internet的通用可靠交付协议——传输控制协议（TCP）之上。因此，HTTP在TCP上的性能受到许多缺陷的影响，这些缺陷都源于TCP的字节流语义经常与用户目标和终端客户端和服务器的性能能力不一致。前面已经提出了一些特别的补救措施来弥补这些缺陷，例如并行连接、持久连接和ackpace。然而，所有这些解决方案都受到向后兼容性假设的过度约束。我们相信，现在是时候采用一种整体的、集成的方法，体现在一种专门为Web定制的新传输协议中。在此，我们提出了一套研究任务来研究、设计、实现、测试和评估我们的新“网络传输协议”（WebTP）。我们的方法基于用户验证、应用语义、网络和客户端状态的概念模型，以及反映这种语法和语义的灵活协议。概念模型强调文档结构、网络状态和用户偏好之间的交互。我们的研究原型将利用已经建立并非常成功的TCP拥塞控制框架，并通过将用户需求引入设计循环，极大地改进现有的web协议。为此，我们将应用应用层框架（ALF）的原则来设计WebTP。ALF表示，为了优化应用程序内部和跨网络的通信路径，应用程序的语义（即其用户需求）应该明确地反映在其网络协议的设计中。尽管实时传输协议（RTP）等现代协议已经采用了ALF，但矛盾的是，它并没有系统地应用于以前存在的应用程序，如Web。我们将研究以下问题：*我们如何在拥塞控制算法、丢失恢复方案、数据包框架方法、报头格式、工具包api等方面最好地构建基于alf的Web协议？这些设计决策如何影响网络性能、用户满意度、协议复杂性和服务器负载？那么客户端如何以最不引人注目的方式引出用户偏好？*接收方（客户端）如何了解服务器的Web数据的内容结构，并将该结构与它对网络状态和用户偏好的估计结合起来，以控制通过WebTP的选择性传输？*功能和状态信息应该如何在源（服务器或代理）、客户端和用户之间分布，以及如何权衡设计和性能？WebTP如何随着速度和客户端的提高而扩展？我们的方法来解决这些问题借鉴了网络工程和通信理论，信号处理和随机控制。我们将使用INDEX项目中现有的网络仿真基础设施来全面测试和评估WebTP。这个项目有可能极大地影响我们对Web传输的看法，并将进一步提供设计方法、实际的协议体系结构以及性能分析和结果。我们相信我们的webtp版本将会有显著的改进，并为进一步的发展铺平道路。