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Re: Should we put the SCTP max message size in the SDP?

From: Salvatore Loreto <salvatore.loreto@ericsson.com>
Date: Sat, 23 Nov 2013 14:51:48 +0000
To: Peter Thatcher <pthatcher@google.com>
CC: Michael Tuexen <Michael.Tuexen@lurchi.franken.de>, Justin Uberti <juberti@google.com>, "public-webrtc@w3.org" <public-webrtc@w3.org>, "mmusic@ietf.org" <mmusic@ietf.org>
Message-ID: <2B9B48179856DC4FA00C93C79EB7E64A336B5E@ESESSMB109.ericsson.se>

(adding mmusic mailing list, sorry for cross posting but if we want to progress the draft
within IETF we have to discuss it in the mmusic mailing list)

the http://tools.ietf.org/html/draft-ietf-mmusic-sctp-sdp-05

still allow to specify the number of streams, even if it is optional

if we want to add also max-message-size attribute, also as on optional one
what about something like this?

a=sctpmap:5000 webrtc-datachannel [streams] [max-message-size]

/Salvatore


On Nov 23, 2013, at 1:35 AM, Peter Thatcher <pthatcher@google.com<mailto:pthatcher@google.com>>
 wrote:




On Fri, Nov 22, 2013 at 3:31 PM, Michael Tuexen <Michael.Tuexen@lurchi.franken.de<mailto:Michael.Tuexen@lurchi.franken.de>> wrote:
On Nov 23, 2013, at 12:16 AM, Peter Thatcher <pthatcher@google.com<mailto:pthatcher@google.com>> wrote:

> Yes, we agreed to forego putting streams in the SDP.  I'm sure I got the syntax of the SDP wrong.  Yours looks better.
and the semantic is: I'm willing to accept SCTP user messages of at least 1000000 bytes, right?


​Correct.​


It makes sense to put it into the SDP...

Best regards
Michael
>
>
> On Fri, Nov 22, 2013 at 2:51 PM, Justin Uberti <juberti@google.com<mailto:juberti@google.com>> wrote:
> I like the idea, but I'm not sure the syntax in http://tools.ietf.org/html/draft-ietf-mmusic-sctp-sdp-04 can express this.
>
> The current a=sctpmap is
>
> a=sctpmap:5000 webrtc-datachannel [streams]
>
> although IIRC we agreed to forego the whole streams negotiation thing.
>
> So we would need something like a=fmtp:5000 max-message-size=1000000.
>
>
> On Fri, Nov 22, 2013 at 2:28 PM, Peter Thatcher <pthatcher@google.com<mailto:pthatcher@google.com>> wrote:
> This is probably going to sound strange coming from me, but I think it might be a better idea to put the SCTP max message size in the SDP.
>
> I'm still OK with having an in-band message (as we discussed during TPAC) to swap the SCTP max message between endpoints, but I was thinking about it a little more and realized that it does involve some extra edge cases and a bit of possible latency.  It would be nice if we could do a handshake earlier on.... and then I realized we can because we can just put it in the SDP where we already do a handshake well ahead of time.
>
> Something like:
>
> a=sctpmap:5000 max-message-size 1000000
>
>
> Obviously I'm not a big fan of stuffing lots of stuff into SDP, but I think this is very minimal and is a more simple solution.
>
>
>
>
> What do you think?
>
>



Received on Saturday, 23 November 2013 14:52:13 UTC

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