Re: [rtcweb] Open data channel issues

Martin Thomson <martin.thomson@gmail.com> Mon, 03 March 2014 06:56 UTC

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Date: Sun, 2 Mar 2014 22:56:54 -0800
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From: Martin Thomson <martin.thomson@gmail.com>
To: Randell Jesup <randell-ietf@jesup.org>
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Cc: Michael Tuexen <tuexen@fh-muenster.de>, "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: Re: [rtcweb] Open data channel issues
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On 2 March 2014 18:42, Randell Jesup <randell-ietf@jesup.org> wrote:
> ndata solves the monopolization issue between streams, allowing packets for
> different streams to be interleaved on the wire.  It does not (so far as I
> know) relax the usrsctp library's returning EMSGSIZE if the sendto() is
> larger than available buffer space, and the alternative (EOR mode) doesn't
> allow for interleaving of messages when sending at all (and I'm not sure it
> allows interleaving on reception either, but I didn't check right now).
>
> Now, this is an implementation/API issue which could be fixed with some
> work, but so far as I know no work has been done on it.  So ndata will allow
> us to expand the max-sending size to min(SCTP_BUFFER_SIZE - N,
> other-sides-max-receive-size).  It does not allow us to expand the size to
> any useful Blob size.

Sounds like the complaint would be best addressed by fixing the SCTP
implementations.  I would hope that ndata would allow for transmission
of messages far in excess of what the implementation is willing to
buffer, that seems arbitrarily restrictive.

(A streaming API wounds like a good idea too.)