Re: [rtcweb] JSEP: Why always offer actpass?

"Makaraju, Maridi Raju (Raju)" <Raju.Makaraju@alcatel-lucent.com> Sun, 30 November 2014 17:18 UTC

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From: "Makaraju, Maridi Raju (Raju)" <Raju.Makaraju@alcatel-lucent.com>
To: =?iso-8859-1?Q?Stefan_H=E5kansson_LK?= <stefan.lk.hakansson@ericsson.com>, Christer Holmberg <christer.holmberg@ericsson.com>, Roman Shpount <roman@telurix.com>
Thread-Topic: [rtcweb] JSEP: Why always offer actpass?
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Date: Sun, 30 Nov 2014 17:18:02 +0000
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Subject: Re: [rtcweb] JSEP: Why always offer actpass?
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> >>> <Raju> When ICE is NOT used, how does the offerer know that the
> >>> answerer does not change the fingerprint and/or transport parameters?
> >>> I guess it does not know. So, offerer has to be prepared for new DTLS
> >>> association by offering actpass. When ICE is used, the answerer can't
> >>> change transport parameter unless offerer does ICE restart (which
> >>> changes offerer transport parameters); Ref [1] is very clear on this
> >>> indicating "DTLS handshake procedure is repeated". However, even when
> >>> ICE is used, I do not find any restriction about answerer not
> >>> changing fingerprint. So, even without ICE restart answerer can
> >>> trigger a DTLS renegotiation by changing its fingerprint.
> >>>
> >>> To conclude all this, IMO whether ICE is used or not, sending actpass
> >>> for all new offers may be cover all possible scenarios.
> >>
> >> That is also my conclusion based on the discussion so far.
> >>
> >> I also think the JSEP draft as far as detailed out is correct, but info
> >> about how the implementation should behave for Subsequent answers is
> >> missing. Text saying that the role must be maintained (unless there is
> >> an ICE restart) should be put in there.
> >
> > <Raju>
> > Hi Stefan,
> > Looks like, there is some misunderstanding here.
> 
> Probably my fault in that case :)
> 
> > My conclusion is to include
> > actpass, but not the previously negotiated role, in all subsequent offers,
> > not just during ICE-restarts.
> 
> I think that is what the JSEP draft says - and my conclusion is that it
> _is_ correct.
> 
> My point was that the _answer_ should (when it is a subsequent answer)
> should say the same role as in previous answers (unless there is an ICE
> restart).

<Raju>
Hi Stefan,
Sorry, it was my misunderstanding in not reading your text correctly.
I did not pay attention to "_answer_" part.
I agree with you that subsequent answers SHOULD (not MUST) keep 
previously negotiated role (except for ICE restarts).
However, as Christer pointed out such clarification belong to SCTP 
SDP draft though.
</Raju>

BR
Raju