Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-protocol-01.txt

On Oct 24, 2013, at 8:36 PM, "Ejzak, Richard P (Richard)" <richard.ejzak@alcatel-lucent.com> wrote:

> Justin, Michael,
> Thanks for the clarifications.  One more question.  What happens if the application tries to select a stream id before the DTLS role is known and it ends up selecting an invalid one?
I'm not completely familiar with the JS API, but if you want to select a stream, aren't
you managing the stream completely on your own. I think the DTLS role stuff is only
relevant if the streams are managed by the browser.
>  
> Michael,
> While it’s true that the data channel control protocol cannot open the channel with the peer before the DTLS role is known, the API allows the application to create the data channel before the DTLS role is known, in which case the sending of the Open message must wait until the SCTP association is established.  I want to know what the application is supposed to do it if needs to create data channels with preselected stream ids before the DTLS role is known.  This seems like something that the spec should make clear rather than leaving it to implementation.
Can you assign the stream ID in the API? Could you point me to the text?

Best regards
Michael
>  
> Thanks,
> Richard
>  
> From: Justin Uberti [mailto:juberti@google.com] 
> Sent: Thursday, October 24, 2013 1:05 PM
> To: Michael Tuexen
> Cc: Ejzak, Richard P (Richard); rtcweb@ietf.org
> Subject: Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-protocol-01.txt
>  
> In Chrome, the stream identifier isn't chosen until the DTLS roles are known; as Michael says, this is fine because the DTLS roles are known before the SCTP association starts up.
>  
> Note that the DTLS roles can change during the lifetime of the call, so the initial role ends up being the one that is used.
>  
> 
> On Thu, Oct 24, 2013 at 10:06 AM, Michael Tuexen <Michael.Tuexen@lurchi.franken.de> wrote:
> On Oct 24, 2013, at 6:59 PM, "Ejzak, Richard P (Richard)" <richard.ejzak@alcatel-lucent.com> wrote:
> 
> > I have a question about draft-ietf-rtcweb-data-protocol-01.  The browser uses DTLS role to determine which side uses even or odd stream identifiers.  What does the application on the side sending the initial SDP offer that establishes the peer connection do if it wants to create data channels before the DTLS role can be determined?  How does the browser know if the application tries to select a disallowed stream id?  If the application asks the browser to select the stream identifier before DTLS role can be determined, what does the browser do?
> Hmm. You can't setup a data channel before you have setup the SCTP association which you
> can't setup before the DTLS handshake is complete. So how do you want to setup a data channel
> before knowing the DTLS role?
> 
> Best regards
> Michael
> >
> > Thanks,
> > Richard
> >
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> > rtcweb@ietf.org
> > https://www.ietf.org/mailman/listinfo/rtcweb
> >
> 
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