Sip Over Websocket - AudioCodes Mediant 4000 SBC User Manual

1. The WebRTC client uses a Web browser to visit the Web site page.
2. The Web page receives Web page elements and JavaScript code for WebRTC from
the Web hosting server. The JavaScript code runs locally on the Web browser.
3. When the client clicks the Call button or call link, the browser runs the JavaScript code
which sends the HTTP upgrade request for WebSocket in order to establish a
WebSocket session with the device. The address of the device is typically included in
the JavaScript code.
4. A WebSocket session is established between the WebRTC client and the device in
order for the WebRTC client to register with the device. This is done using a SIP
REGISTER message sent over the WebSocket session (SIP over WebSocket).
Registration can be initiated when the client enters credentials (username and
password) on the Web page or it can be done automatically when the client initially
browses to the page. This depends on the design of the Web application (JavaScript).
5. Once registered with the device, the client can receive or make calls, depending on
the Web application.
6. To make a call, the client clicks the call button or link on the Web page.
7. Negotiation of a workable IP address between the WebRTC client and the device is
done through ICE.
8. Negotiation of SRTP keys using DTLS is done between WebRTC and the client on the
media.
9. Media flows between the WebRTC client and the SIP client located behind the device.

29.4.1 SIP over WebSocket

The device supports the transmission of SIP signaling over WebSocket. WebSocket is a
protocol providing real-time, full-duplex (two-way) communication over a single TCP
connection (socket) between a Web browser or page (client) and a remote host (server).
This is used for browser-based applications such as click-to-call from a Web page. As
User's Manual 568
Mediant 4000 SBC
Document #: LTRT-40203