RTCWeb Evolution

利用因特网进行综合音视频通信的情况正在大量增加。目前，存在多种专有解决方案，例如Skype、Facetime或b谷歌Hangouts。这些解决方案的一个重要限制是它们需要安装专有软件，并且它们不能互操作。因此，IETF和W3C正在合作开发一种网络浏览器的标准化扩展，使媒体（音频/视频）和非媒体（一般数据）应用程序数据的浏览器之间能够直接实时通信。通信协议由IETF工作组RTCWeb定义，而编程接口（Javascript API）由W3C工作组WebRTC开发。目前由IETF指定的RTCWeb协议栈必须在NAT边界（网络地址转换）上为媒体和非媒体流提供安全通信。为了实现这一点，现有的协议以一种新的方式组合在一起。具有拥塞控制功能的传输协议SCTP（流控制传输协议）是RTCWeb体系结构的关键构建块之一，也是本项目的重点。在项目期间，将对RTCWeb环境中现有协议的新组合进行评估、改进和系统扩展。特别的科学兴趣是如何协调和控制RTCWeb上下文中各种媒体和非媒体流的问题，同时考虑到它们的异构需求和属性，以便为用户提供预期的行为。RTCWeb在一个应用程序中组合了各种流。这提供了以主动和目标导向的方式协调相关机制（特别是拥塞控制）的机会。应制定和评价利用这一资源的各种办法。项目合作伙伴的初步调查已经表明，SCTP的标准拥塞控制无法保护媒体流免受并发非媒体流的影响。因此，在工程项目中，须发展及评估其他的挤塞控制措施。除了单独考虑SCTP拥塞控制外，还应考虑目前提出的关于媒体流拥塞控制的方法以及访问路由器的主动队列管理机制。这些非常多样化的机制目前是单独发展的，它们之间的相互作用是一个尚未得到系统评价的关键方面。该项目的目标是通过有针对性的评估，结合协调拥塞控制的概念和机制的发展，实现整个系统的显著性能改进。

The use of the Internet for integrated audio and video communication is increasing substantially. At the moment, there exist multiple proprietary solutions, e.g. Skype, Facetime or Google Hangouts. A significant limitation of these solutions is that they require the installation of proprietary software and that they are not interoperable. Therefore, the IETF and the W3C are working together in order to develop a standardized extension of web browsers enabling a direct real-time communication between browsers for media (audio/video) and non-media (general data) application data. The communication protocols are defined by the IETF working group RTCWeb, whereas the programming interface (Javascript API) is developed by the W3C working group WebRTC. The protocol stack currently being specified by the IETF under the name RTCWeb has to provide a secure communication over NAT boundaries (Network Address Translation) for media as well as non-media streams. To achieve this, already existing protocols are combined in a new way. The transport protocol SCTP (Stream Control Transmission Protocol) with its congestion control feature is one of the key building blocks of the RTCWeb architecture and is in the focus of this project. The novel combination of existing protocols in the RTCWeb context will be evaluated, improved and extended systematically during the project. Of particular scientific interest is the question how to coordinate and control the various media and non-media streams in the RTCWeb context taking into account their heterogeneous requirements and properties in order to provide the expected behavior for the user. RTCWeb combines the various streams within one application. This provides the opportunity to coordinate the involved mechanisms - in particular congestion controls - in an active and target-oriented way. Options to exploit this shall be developed and evaluated. Initial investigations of the project partners have already shown that the standard congestion control of SCTP is not able to protect the media streams from concurrent non-media streams. Therefore, alternative congestion controls shall be developed and evaluated in the project. In addition to the consideration of the SCTP congestion control alone also the currently proposed methods with respect to congestion control for media streams as well as the active queue management mechanisms for access routers shall be taken into account. These very diverse mechanisms are currently developed separately and their interaction is a crucial aspect which has not yet been evaluated systematically. The goal of the project is to achieve a significant performance improvement of the overall system by means of targeted evaluations in combination with the development of concepts and mechanisms for coordinated congestion control.