Web Browser for RTC
Abstract |
WebRTC Browser |
Authors |
Walter Fan |
Status |
WIP as draft |
Category |
LearningNote |
Updated |
2024-08-21 |
简介
现在的主流浏览器主要有 Chrome, Edge, Firefox 和 Safari, 基本上都应用了 libwebrtc, 所以在 WebRTC 的功能上大同小异 其中 Chrome 对 WebRTC 的支持是最好的。
Browser Model 浏览器模型
+------------------------+ On-the-wire
| | Protocols
| Servers |--------->
| |
| |
+------------------------+
^
|
|
| HTTPS/
| WebSockets
|
|
+----------------------------+
| JavaScript/HTML/CSS |
+----------------------------+
Other ^ ^ RTC
APIs | | APIs
+---|-----------------|------+
| | | |
| +---------+|
| | Browser || On-the-wire
| Browser | RTC || Protocols
| | Function|----------->
| | ||
| | ||
| +---------+|
+---------------------|------+
|
V
Native OS Services
Figure 1: Browser Model
Browser RTC Trapezoid 浏览器实时通信三角
+-----------+ +-----------+
| Web | | Web |
| | | |
| |------------------| |
| Server | Signaling Path | Server |
| | | |
+-----------+ +-----------+
/ \
/ \ Application-defined
/ \ over
/ \ HTTPS/WebSockets
/ Application-defined over \
/ HTTPS/WebSockets \
/ \
+-----------+ +-----------+
|JS/HTML/CSS| |JS/HTML/CSS|
+-----------+ +-----------+
+-----------+ +-----------+
| | | |
| | | |
| Browser |--------------------------------| Browser |
| | Media Path | |
| | | |
+-----------+ +-----------+
Figure 2: Browser RTC Trapezoid
Web browser RTC functionality
Data transport:
For example, TCP and UDP, and the means to securely set up connections between entities, as well as the functions for deciding when to send data: congestion management, bandwidth estimation, and so on.
Data framing:
RTP, the Stream Control Transmission Protocol (SCTP), DTLS, and other data formats that serve as containers, and their functions for data confidentiality and integrity.
Data formats:
Codec specifications, format specifications, and functionality specifications for the data passed between systems. Audio and video codecs, as well as formats for data and document sharing, belong in this category. In order to make use of data formats, a way to describe them (e.g., a session description) is needed.
Connection management:
For example, setting up connections, agreeing on data formats, changing data formats during the duration of a call. SDP, SIP, and Jingle/XMPP belong in this category.
Presentation and control:
What needs to happen in order to ensure that interactions behave in an unsurprising manner. This can include floor control, screen layout, voice-activated image switching, and other such functions, where part of the system requires cooperation between parties. Centralized Conferencing (XCON) [RFC6501] and Cisco/Tandberg’s Telepresence Interoperability Protocol (TIP) were some attempts at specifying this kind of functionality; many applications have been built without standardized interfaces to these functions.
Local system support functions:
Functions that need not be specified uniformly, because each participant may implement these functions as they choose, without affecting the bits on the wire in a way that others have to be cognizant of. Examples in this category include echo cancellation (some forms of it), local authentication and authorization mechanisms, OS access control, and the ability to do local recording of conversations.
参考资料
RFC8825: Overview: Real-Time Protocols for Browser-Based Applications