Determining the signalling overhead of two common WebRTC methods: JSON via XMLHttpRequest and SIP over WebSocket

Web Real-Time Communication (WebRTC) introduces real-time multimedia communication as native capabilities of Web browsers. With the adoption of WebRTC the Web browsers will be able to use WebRTC to communicate with one another (peer-to-peer), and with WebSocket servers such as Mobicents SIP Servlets and other server technologies that support WebSocket communication to enable SIP-to-WebRTC communication. This paper outlines the potential of WebRTC and discusses the two common methods of doing real-time communication in Web browsers through WebRTC. The methods are JavaScript Object Notation (JSON) via XMLHttpRequest (XHR) and Session Initiation Protocol (SIP) via WebSocket. A three-user WebRTC video chat prototype application was developed and used to evaluate both methods. Additional signalling overhead introduced into a browser by each method was determined. The results showed WebRTC-SIP/WS has more overhead than WebRTC-JSON/XHR. These signalling overhead findings are useful in that they could help application developers make decision on their choice of technologies and protocols when developing WebRTC-supported applications.

I. INTRODUCTION

The Internet Engineering Task Force (IETF) and the World Wide Web Consortium (W3C) are currently tasked with bringing WebRTC among browsers to an acceptable level in both the industry and the academia. WebRTC is an open framework that offers web application developers the ability to write rich real-time multimedia applications (e.g. video and gaming applications) on the web without requiring plugins or extensions. Its purpose is to help build a strong Real Time Communication (RTC) platform that works across multiple web browsers and platforms. In an implementation, the WebRTC API will abstract several key components for real-time audio, video, networking and signal [1], [2]. While the IETF is standardizing the signalling protocols and media technologies (e.g. codecs) required in WebRTC, the W3C is standardizing the APIs and browsers for real time communication.