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Re: [rtcweb] #13: Transport of DATA_CHANNEL_OPEN

Martin Thomson <martin.thomson@gmail.com> Thu, 18 April 2013 19:40 UTC

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Date: Thu, 18 Apr 2013 12:40:35 -0700
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From: Martin Thomson <martin.thomson@gmail.com>
To: Michael Tuexen <Michael.Tuexen@lurchi.franken.de>
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Cc: "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: Re: [rtcweb] #13: Transport of DATA_CHANNEL_OPEN
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On 18 April 2013 11:30, Michael Tuexen <Michael.Tuexen@lurchi.franken.de> wrote:
> I think you are looking for some kind of "reliable opening a datachannel".
> That was provided by the three way handshake. But the working group decided
> that this kind of setup is not required...

I certainly don't want this.  If you recall, I advocated for no OPEN
message at all.

> I think the OPEN can only be sent if both streams (incoming / outgoing) are
> are available.

Yes, that would at least make it possible to indicate an error (except
if the error is that an OPEN is received with no available return
stream ;)

> I suggested an Error message already several times. Also
> for other things like reception of unsupported message types, unexpected messages,
> message formatting issues, ...

Those at least are application-layer error conditions.  No need to add
anything at the OPEN/ERROR layer for those.  Applications can provide
their own feedback path for those.

> There are several error condition. I think
> the alternative suggested was to reset the streams. However, for the peer there
> is no way to figure out why the data channel was closed if something was lost.

Exactly the point: not knowing would be bad because it would make data
channels untrustworthy.  Occasionally you would lose a channel and all
the data you sent on it with no way, other than asking your peer, of
knowing what got through.

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