Re: [MMUSIC] updating draft-ietf-mmusic-sctp-sdp

[Paul Kyzivat <[e-mail]>]

Salvatore,

Comment/question inline

On 10/8/12 4:12 AM, Salvatore Loreto wrote:
> Hi there,
>
> there has been a quite large discussion within the rtcweb mailing list and
> especially the w3c webrtc mailing list.
>
> Some of the points discussed are specific of how to negotiate the
> 'datachannel' protocol over SDP,
> and I lean on putting those in a separate draft and not in this one.
>
> However there are things that are general enough to is worth to insert
> in this draft
> as they can be used in other protocols that eventually will be specified
> in the future
> running on top of SCTP, or STCP over DTLS.
>
>   'streams' is some of those attributes,
>   so I am proposing to insert in the new version of the draft the
> following text
>
>   xxx.  Streams Attribute
>
>     The 'streams' attribute indicates time the number of streams to be supported by the association.
>     If this attribute is not present, the implementation should provide a default, with a suggested value
>     of 16.
>
>
>           streams-attr           =  "a=streams:" streamsnumbers
>           streamsnumbers         =1*DIGIT
>
>
> As I said, all the other attributes that has been discussed are tied to
> the 'datachannel'  protocol identifier ( to be registered?),
> which is describing the format of the media... so they should go in a
> different draft.

I'm confused by the above. The m-line syntax is:

     m=<media> <port> <proto> <fmt> ...

and this draft is defining SCTP, SCTP/DTLS and DTLS/SCTP values for 
<proto>. Are you suggesting that "datachannel" be defined (in a 
different draft) as an alternative to *these* values? I would think it 
would make more sense to define "datachannel" as a <fmt> value.

That brings up another issue:

According to 4566, the values of the <fmt> field are protocol specific. 
That means that *this* draft needs to specify how <fmt> values are to be 
understood for sctp. That is actually a problem, one might want 
different fmt semantics for each channel.

I have more to say, but I'll start another thread for that.

	Thanks,
	Paul