Re: [rtcweb] Review comments on draft-ietf-rtcweb-data-protocol-03

"Makaraju, Maridi Raju (Raju)" <Raju.Makaraju@alcatel-lucent.com> Tue, 04 March 2014 19:24 UTC

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From: "Makaraju, Maridi Raju (Raju)" <Raju.Makaraju@alcatel-lucent.com>
To: Paul Kyzivat <pkyzivat@alum.mit.edu>, "rtcweb@ietf.org" <rtcweb@ietf.org>
Thread-Topic: [rtcweb] Review comments on draft-ietf-rtcweb-data-protocol-03
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Date: Tue, 4 Mar 2014 19:24:22 +0000
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Subject: Re: [rtcweb] Review comments on draft-ietf-rtcweb-data-protocol-03
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> >> 2. Section 4:
> >>
> >> The method
> >>    used to determine which side uses odd or even is based on the
> >>    underlying DTLS connection role when used in WebRTC, with the side
> >>    acting as the DTLS client using even stream identifiers.
> >>
> >> Isn't this unnecessary using the vague word of WebRTC instead of simply
> >> pointing to the DTLS roles of the established data channel?
> > The point is that in the WebRTC you use DCEP/SCTP/DTLS/UDP and therefore
> > you can refer to the DTLS role. However, you could use DCEP/SCTP/IP
> > or DCEP/SCTP/UDP/IP or DCEP/SCTP over something not involving DTLS.
> > In that case DTLS is not used and you can not refer to the DTLS role.
> > That is why the restriction is used.
> 
> So data channels could work over SCTP/IP or SCTP/UDP/IP, but in fact
> can't solely because the choice of even/odd role is dependent on DTLS
> connection role?
> 
> Couldn't you find a way to choose the even/odd role based solely on the
> SCTP layer and the SDP? Then data channels could be used over those
> other stacks.
[Raju] 
+1
a=setup could be used to determine this, but the final determination is done only at SDP answer (which is same for DTLS).
For DTLS/SCTP case since both DTLS and SCTP layers use the same a=setup, both DTLS and SCTP client/servers roles match.
So, DCEP changing text to indicate role determination be done per SCTP client/server role instead of DTLS role may just work and is compatible with existing text.
[/Raju]

Best Regards
Raju