WebRTC Architecture
WebRTC extends the client-server semantics by introducing a peer-to-peer communi‐
cation paradigm between browsers. The most general WebRTC architectural model (see
Figure 1-1) draws its inspiration from the so-called SIP (Session Initiation Protocol)
Trapezoid (RFC3261).
Figure 1-1. The WebRTC Trapezoid
In the WebRTC Trapezoid model, both browsers are running a web application, which
is downloaded from a different web server. Signaling messages are used to set up and
terminate communications. They are transported by the HTTP or WebSocket protocol
via web servers that can modify, translate, or manage them as needed. It is worth noting
that the signaling between browser and server is not standardized in WebRTC, as it is
considered to be part of the application (see “Signaling” on page 5). As to the data path,
a PeerConnection allows media to flow directly between browsers without any inter‐
vening servers. The two web servers can communicate using a standard signaling pro‐
tocol such as SIP or Jingle (XEP-0166). Otherwise, they can use a proprietary signaling
protocol.
The most common WebRTC scenario is likely to be the one where both browsers are
running the same web application, downloaded from the same web page. In this case
the Trapezoid becomes a Triangle (see Figure 1-2).
2 | Chapter 1: Introduction
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