[RTW] [dispatch] Does RTC-WEB need to pick a signaling protocol?

[Markus.Isomaki at nokia.com]

Hi Justin,

I’m not sure I fully understand the task b) that you describe below. You are not talking about a representation/mechanism for a wire protocol, but something related to the API? I mean, if everyone is going to define and implement their own “signaling” protocol on HTTP or websockets, what is it exactly that would need to be standardized?

If we use webmail as an example, there has been no need to define any mapping/format related to SMTP. So if that case is analogous to this one, why we need to do something different here? I know that the difference is that in RTC-Web we want to establish media streams end-to-end between the browsers, unlike in e-mail. So, the cases are not fully analogous after all. Some elaboration on that point would help many people to understand the RTC-Web need better, I think.

Thanks,
Markus


From: dispatch-bounces at ietf.org [mailto:dispatch-bounces at ietf.org] On Behalf Of ext Justin Uberti
Sent: 02 February, 2011 08:47
To: Matthew Kaufman
Cc: rtc-web at alvestrand.no; DISPATCH list
Subject: Re: [dispatch] [RTW] Does RTC-WEB need to pick a signaling protocol?

Great example.

And just like Gmail uses an SMTP gateway to connect its own HTTP-based protocol to the rest of the world, Gmail voice and video uses a XMPP gateway to connect its HTTP-based signaling to other XMPP clients. Others in this space have done similar things by implementing XMPP clients in Javascript.

So I think we have existence proofs that this approach, in addition to being extremely flexible, is entirely workable today.

The two things that we need to specify are
a) the semantics of the signaling (i.e. the offer-answer mechanism that both SIP and XMPP are patterned around)
b) the mechanism through which session offers and answers will be described (e.g. some SDP-ish thing that is suitable for the web).

a) seems rather straightforward. b) will likely be trickier - we need something that can be mapped to SDP, for SIP gateways, but we probably want it to be represented as JSON for benefit of web developers. So the challenge becomes, what format can we define that can be unambiguously mapped to/from SDP, but doesn't bring with it all of the baggage of SDP?

--justin
On Mon, Jan 31, 2011 at 8:12 AM, Matthew Kaufman <matthew.kaufman at skype.net<mailto:matthew.kaufman at skype.net>> wrote:
On 1/29/2011 6:35 AM, Jonathan Rosenberg wrote:

That said, even if one asks the question of whether it is a good idea for us to pick something, I think the answer is no. The enormous benefit of the web model is its ability for innovation and velocity. Standardization is not needed for communications within the domain of the provider; new features can be developed and deployed as quickly as they can be conceived.

Agreed. Consider the case of Gmail (or any other web-based email)

Did every web browser on the planet need to be upgraded to speak IMAP or SMTP in order for Gmail to be implemented? No.

Does the JavaScript that Gmail sends down to your browser in order to implement its UI need to be standardized among web email platforms? No.

Does Google need to use the same JavaScript libraries and PHP back-end that SquirrelMail uses in order to implement a web email application? No.

Can Google change that JavaScript tomorrow without breaking interoperability? Yes, and they probably will.

But could Gmail be as successful without the worldwide SMTP infrastructure it ties in to? Probably not.

I see the same situation here. A web browser with real-time communication capabilities will work in conjunction with a web site that serves up the HTML and JavaScript that makes up the calling application. For some applications, this will be sufficient. For others, one will want to implement SIP or XMPP/Jingle or something else in order to gateway these calls to other networks. The SIP implementation can live in the JavaScript, up in the web server, in a separate gateway, or any combination thereof.

Matthew Kaufman

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