Re: [rtcweb] *MUST* DCEP?

[Paul Kyzivat <[e-mail]>]

On 3/4/14 12:08 PM, Makaraju, Maridi Raju (Raju) wrote:
> While a=sctpmap assumes use of DCEP, indication of external negotiation
> (instead of DCEP) also requires subprotocol and it’s parameters to be
> conveyed. This has to be done per data channel stream.
>
> Are you looking at more than what is documented in
> [I-D.ejzak-mmusic-data-channel-sdpneg]?
>
> Or are you looking for an indication of this (for all streams) directly
> in a=sctpmap?

I'm ok as things currently stand, though the documents are confusing.
The 'a=sctpmap:nnn websocket-datachannel' means that DCEP is supported.

My concern was a proposal I think I heard that would make support for 
DCEP to be optional. In that case, IMO it is important that the O/A 
exchange establish whether DCEP is supported or not.

	Thanks,
	Paul

> How about item 3 of the following proposal?
>
> http://www.ietf.org/mail-archive/web/mmusic/current/msg13155.html
>
> -Raju
>
> *From:*rtcweb [mailto:[e-mail]] *On Behalf Of *Ted Hardie
> *Sent:* Tuesday, March 04, 2014 5:17 AM
> *To:* Paul Kyzivat
> *Cc:* [e-mail]
> *Subject:* Re: [rtcweb] *MUST* DCEP?
>
> On Tue, Mar 4, 2014 at 11:03 AM, Paul Kyzivat <[e-mail]
> <mailto:[e-mail]>> wrote:
>
>     Ted,
>
>     (I think this was open issue #8)
>
>     You closed discussion on this, saying that this should be specified
>     in some rtcweb "system" document. IIUC, then I disagree.
>
>     This is important to others besides rtcweb. We want to use this
>     mechanism, both with and without components that are implementing
>     rtcweb. Certainly for non-browsers.
>
> Help me understand why it wouldn't then be in their systems documents?
>
> Ted
>
>
>
>     This ultimately comes down to what I can expect after having
>     negotiated (in SDP) the establishment of an SCTP association. When
>     doing so, I use a=sctpmap to negotiate the how the association will
>     be used. If I intend to use data channels and DCEP then I want an
>     assurance that the other end does too. (That is the purpose of the
>     SDP negotiation.)
>
>     AFAIK, current when I specify 'a=sctpmap:webrtc-datachannel' (or
>     'a=sctp-datachannel' depending on where I look), that means the
>     other side supports data channels *and* guarantees support for DCEP.
>     There is no means to indicate support for data channels *without* DCEP.
>
>     I don't see any urgent need to have data channels without DCEP, as
>     long as *use* of DCEP is optional.
>
>     IMO things would be less confusing if the two documents were merged
>     into one, that defines the *Data Channel Protocol* (that runs over
>     SCTP). This protocol runs over pairs of SCTP streams, has a small
>     number of messages (open, ack, string-payload, binary-payload,
>     close), and encodes them in SCTP using SCTP messages with particular
>     payloads and SCTP stream reset. The open and ack messages would be
>     optional.
>
>              Thanks,
>              Paul
>