Re: [rtcweb] Asking TLS for help with media isolation

Paul Kyzivat <> Thu, 10 April 2014 14:51 UTC

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Date: Thu, 10 Apr 2014 10:51:43 -0400
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Subject: Re: [rtcweb] Asking TLS for help with media isolation
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On 4/10/14 4:56 AM, Harald Alvestrand wrote:
> On 04/08/2014 08:24 PM, Martin Thomson wrote:
>> On 8 April 2014 09:50, Bernard Aboba <> wrote:
>>> [BA] I'm not sure that the concept of "isolation" makes sense for those
>>> intermediaries (or to voicemail or an audio/video conference, for that
>>> matter).   While in a point-to-point call it might be useful, in a
>>> conference the whole point is to have audio/video sent to multiple
>>> parties,
>>> and recording is commonplace.  The problem is that from a protocol
>>> point of
>>> view the cases are not easily distinguishable -- and so if the browser
>>> insists on "isolation" then one wonders what will happen if the
>>> conference
>>> bridge/video MCU/voicemail system refuses to negotiate it.   Refusing to
>>> send media would not be a desirable outcome.
>> I think that for this, it's perfectly reasonable to use identity, but
>> not stream isolation.  With isolation, if the peer does not agree to
>> comply, then the session fails to complete.
> Actually I'd say it's "if the peer does not *agree to* comply".
> The protocol has no defense against liars, but that's a common issue.
>> The authenticated party here is an MCU (or bridge, or voicemail,
>> etc...).  Rather than sending to "", media is
>> sent to "".  Is it reasonable for that MCU to forward
>> media to other, unspecified entities?  Clearly it can, but should it?
>> (Not having thought it through completely, a voicemail box could
>> conceivably work.  I think that I'd want to use a different identity
>> for it though.)
> I can see an use for a recording spec that said "you can record this,
> but only if you do it in such a way that it's only accessible to the
> stated identity".
> Would be weird to try to enforce that.... but I agree; MCU and isolation
> have a hard time mixing.
> Let's just not.

So what does this mean for screen sharing with a conference?