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

(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?
>
>