Microsoft has published a working prototype of CU-RTC-Web, its proposed specification for enabling browser-based, plugin-free, real-time audio and video communication.
CU-RTC-Web isn’t the only proposal for such a specification. In fact, it’s not even the main one. The World Wide Web Consortium (W3C), the group that formalizes the development and specification of Web-related standards, has its own group working on a plugin-free, real-time audio and video communication specification called WebRTC. Preliminary—and somewhat rudimentary—support for WebRTC is found in current versions of Chrome and Firefox.
This support certainly isn’t finished yet, and interoperability between the browsers remains troublesome—many of the online WebRTC demos are built for Chrome alone and won’t work with Firefox at all—but in theory they’re on track to support the same specification in a manner that will eventually be compatible.
Redmond first announced CU-RTC-Web in August. Along with the specification itself, the company produced a rationale; a list of reasons why it felt that WebRTC was a bad fit for the problem at hand, and why CU-RTC-Web was a superior solution. Perhaps the most specific complaint was that WebRTC was quite deeply linked to a specification called SDP, an open industry standard used extensively for VoIP and video conferencing systems in conjunction with SIP, with Microsoft arguing that this is over-complicated and hinders interoperability with non-SDP systems. SDP is used to negotiate the parameters of the connection; things like the bandwidth, the IP addresses and port numbers to use, and so on.
It just happens that Microsoft has non-SDP products of its own—Skype (which remains stubbornly proprietary and undocumented) and Lync (which can bridge with SIP systems, and hence understands SDP, but offers alternative APIs too).
Although W3C’s WebRTC working group acknowledged that the current WebRTC spec has parts that are as-yet incomplete, a vote carried out in September to choose between the two paths was heavily in favor of WebRTC. It won with 22 votes to just 4 for Microsoft’s proposal.
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