Re: [MMUSIC] Data channel dcsa attribute usage and IANA

[Christer Holmberg <[e-mail]>]

Hi,

>>>> Section 7.2 of draft-ietf-mmusic-msrp-usage-data-channel updates the 
>>>> IANA registry for the SDP ‘setup’ attribute, by indicating that it 
>>>> can be used inside an SDP ‘dcsa’ attribute.
>>>>
>>>> Do we really need to update the IANA registry for all SDP attributes 
>>>> that can be included in an ‘dcsa’ attribute???
>>>
>>> I think so. Look at RFC4566bis for the revised attribute registry.
>>>
>>> The way to avoid this would be to remove "Usage Level" from the 
>>> registry and thus force people to consult the defining documents for 
>>> the attribute in order to learn this. But it is seriously late in the cycle to update 4566bis.
>> 
>> I think it can be seen in two different ways, that have no impact on 4566bis.
>> 
>> 1) If the usage level is "media", that doesn't change inside a dcsa 
>> attribute. From an SDP perspective it is still "media", as it is part 
>> of an m= line. If you place a "session" level attribute inside a dcsa 
>> attribute that changes, but I don't think we do that; or
>> 
>> 2) From an SDP perspective, only the dcsa attribute is used. What's inside is "application specific", and has nothing to do with SDP.
>
> I think you are mixing two things here:
>
> - what currently is required based on the specs as written (including 4566bis);
>
>- what would be the ideal way for it to work.
>
> Based on the current specs I think the registry must be updated. And I think that was always expected during the development of the dcsa attribute.

draft-mmusic-data-channel-sdpneg doesn't say anything (unless I've missed it) about updating the IANA registry, so I am not sure what specs you are referring to.

>What is most important is that people have a well defined way to determine whether an attribute can be used in dcsa in a particular case. 

Sure, but that is defined in the data channel usage specs (e.g., the MSRP usage spec and the T.140 usage spec).

>If they are expected to find this in a document defining the attribute, then the document had better provide an answer.

We are not updating the documents defining the attributes.

>If you feel a change is needed to 4566bis then we will have to figure out if and how to accomplish that. It is already at the editor.

I don't think a change is needed for 4566bis.  But, if an IANA registry update is required for attributes used with dcsa I think it should be said in draft-mmusic-data-channel-sdpneg (unless it's already there and I've missed it...)

Regards,

Christer