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

On Nov 23, 2013, at 3:51 PM, Salvatore Loreto <salvatore.loreto@ericsson.com> wrote:

> 
> (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]
... and what is the semantic if max-message-size is not provided? The endpoint
is willing to accept arbitrary large messages?

I also suggest to rename max-message-size to supported-message-size.
The semantics is that the end-point is willing to accept messages up to
supported-message-size. It does not make a statement about messages larger
than the limit. Calling it max-message-size suggests to me, that messages
larger than the limit can't be handled...

Best regards
Michael
> 
> /Salvatore
> 
> 
> On Nov 23, 2013, at 1:35 AM, Peter Thatcher <pthatcher@google.com>
>  wrote:
> 
>> 
>> 
>> 
>> On Fri, Nov 22, 2013 at 3:31 PM, Michael Tuexen <Michael.Tuexen@lurchi.franken.de> wrote:
>> On Nov 23, 2013, at 12:16 AM, Peter Thatcher <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> 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> 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 15:19:41 UTC