Re: [MMUSIC] IANA registration of SDP attributes

Christian Groves <Christian.Groves@nteczone.com> Tue, 22 March 2016 01:21 UTC

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To: mmusic@ietf.org, Flemming Andreasen <fandreas@cisco.com>, Bo Burman <bo.burman@ericsson.com>
References: <56E1C193.1050308@alum.mit.edu> <56E2EF31.2020808@alcatel-lucent.com> <56E2F67D.7060005@alum.mit.edu> <56EE0AA1.3030502@nteczone.com> <56EEE286.5090505@alum.mit.edu>
From: Christian Groves <Christian.Groves@nteczone.com>
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Date: Tue, 22 Mar 2016 12:21:07 +1100
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Archived-At: <http://mailarchive.ietf.org/arch/msg/mmusic/W1uaJaY-uepKzBbtj5cwWnOA8Ug>
Subject: Re: [MMUSIC] IANA registration of SDP attributes
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Hello Paul,

Yes I think it is fuzzy. draft-ietf-mmusic-sctp-sdp is using a=setup for 
SCTP, by the definition below it would need to update the registry to 
add a reference. There's probably other attributes where this is the 
case also (e.g. a=connection). For consistency all the existing 
attributes would need to be checked when reformatting the registry.

I do agree that it would be nice to have a link from each SDP attribute 
to the RFCs that are using it but I think the genie is out of the bottle 
on this one.

With the light agenda maybe this is something to discuss in Argentina?

Regards, Christian

On 21/03/2016 4:48 AM, Paul Kyzivat wrote:
> On 3/19/16 10:27 PM, Christian Groves wrote:
>> With the current registry don't only documents that introduce NEW
>> attributes get included in the registry?
>>
>> dcsa (MSRP) and dcsa (BFCP) don't define new attributes they use setup.
>> This is similar to the fact that multiple protocols at the media level
>> use a=setup but we don't add references to them in the registry.
>>
>> So do we now say that if a draft/RFC uses an existing media level
>> attribute in a DCSA that must be added to the registry with a dcsa
>> indication?
>
> ISTM that a document that broadens the applicability of an attribute 
> ought to be recorded in the registry.
>
> I expect that this is a bit fuzzy. For instance, the use of setup with 
> TCP was defined. If a new proto of 'TCP/FOO' is defined that runs over 
> TCP, and simply uses setup for establishing the TCP part, then maybe 
> it doesn't need to be recorded in the registry.
>
> But if setup is used for something other than TCP, or also used for 
> some semantic over and above its use for TCP, then it surely ought to 
> be recorded. (For instance, when it is used to control initialization 
> of some other protocol over TCP.)
>
> I expect that this is less than clear, and may be controversial. Seems 
> to need more discussion.
>
>     Thanks,
>     Paul
>
>> Regards, Christian
>>
>> On 12/03/2016 3:46 AM, Paul Kyzivat wrote:
>>> On 3/11/16 11:15 AM, Juergen Stoetzer-Bradler wrote:
>>>> Paul,
>>>>
>>>> The last alternative would have the advantage that different 
>>>> subprotocol
>>>> documents could be referenced for the same attribute. Like e.g. for 
>>>> the
>>>> setup attribute (if there were BFCP over data channel transport 
>>>> specific
>>>> aspects):
>>>>
>>>> *SDP Name*     *Level(s)*     *Reference(s)*
>>>> accept-types
>>>>     media,
>>>> dcsa(MSRP)
>>>>     [RFC4975]
>>>> [draft-ietf-mmusic-msrp-usage-data-channel]
>>>> cat
>>>>     session
>>>>     [RFC4566]
>>>> fmtp
>>>>     media,source     [RFC4566][RFC5576]
>>>> mediaclk
>>>>     session,media,source
>>>>     [RFC7273]
>>>> ptime
>>>>     media
>>>>     [RFC4566]
>>>> recvonly
>>>>     session,media,
>>>> dcsa(MSRP)
>>>>     [RFC4566][RFC4975]
>>>> [draft-ietf-mmusic-msrp-usage-data-channel]
>>>> setup
>>>>     session, media
>>>> dcsa(MSRP)
>>>> dcsa(BFCP)
>>>>     [RFC4145]
>>>> [draft-ietf-mmusic-msrp-usage-data-channel]
>>>> [draft-schwarz-mmusic-bfcp-usage-data-channel]
>>>>
>>>>
>>>> Therefore I'd be in favor of your last alternative.
>>>
>>> Let's see what other comments we get, especially from Flemming.
>>>
>>> Then, if this is preferred direction we can work on refining it.
>>>
>>>     Thanks,
>>>     Paul
>>>
>>>> Thanks,
>>>> Juergen
>>>>
>>>>
>>>> On 10.03.2016 19:48, EXT Paul Kyzivat wrote:
>>>>> [splitting off from the thread on data-channel-sdpneg]
>>>>>
>>>>> Currently IANA has five(!) separate registries for sdp attributes:
>>>>>
>>>>> att-field (session level)
>>>>> att-field (both session and media level)
>>>>> att-field (media level only)
>>>>> att-field (source level)
>>>>> att-field (unknown level)
>>>>>
>>>>> They all have the same format:
>>>>>
>>>>> *Type**
>>>>> *     *SDP Name**
>>>>> *     *Reference**
>>>>> *
>>>>> att-field (session level)     cat     [RFC4566]
>>>>> att-field (both session and media level)     recvonly
>>>>>     [RFC4566]
>>>>> att-field (both session and media level)     mediaclk
>>>>>     [RFC7273]
>>>>> att-field (media level only)     accept-types
>>>>>     [RFC4975]
>>>>> att-field (media level only)     fmtp
>>>>>     [RFC4566]
>>>>> att-field (source level)     fmtp
>>>>>     [RFC5576]
>>>>>
>>>>>
>>>>> This format is a pain, because it is hard to look an attribute up if
>>>>> you don't know at what level(s) it is valid. It also has the 
>>>>> potential
>>>>> to allow an attribute name to be registered for unrelated purposes if
>>>>> the type is different. (IMO that would be bad.)
>>>>>
>>>>> A long time ago (several years now), as part of the 4566bis work, I
>>>>> proposed that these tables be merged into one. It was my impression
>>>>> that this was agreed and would be done. But I don't recall any
>>>>> agreement on the logistics of doing so.
>>>>>
>>>>> My thought was that the combined table would look like:
>>>>>
>>>>> *SDP Name*     *Level(s)*     *Reference(s)*
>>>>> accept-types
>>>>>     media
>>>>>     [RFC4975]
>>>>> cat
>>>>>     session
>>>>>     [RFC4566]
>>>>> fmtp
>>>>>     media,source     [RFC4566][RFC5576]
>>>>> mediaclk
>>>>>     session,media,source
>>>>>     [RFC7273]
>>>>> ptime
>>>>>     media
>>>>>     [RFC4566]
>>>>> recvonly
>>>>>     session,media
>>>>>     [RFC4566]
>>>>>
>>>>>
>>>>>
>>>>> Then we get to data channel attributes. My thought is to incorporate
>>>>> them into this table structure, as yet another "level". E.g.,
>>>>>
>>>>> *SDP Name*     *Level(s)*     *Reference(s)*
>>>>> accept-types
>>>>>     media,dcsa
>>>>>     [RFC4975][draft-ietf-mmusic-msrp-usage-data-channel]
>>>>> cat
>>>>>     session
>>>>>     [RFC4566]
>>>>> fmtp
>>>>>     media,source     [RFC4566][RFC5576]
>>>>> mediaclk
>>>>>     session,media,source
>>>>>     [RFC7273]
>>>>> ptime
>>>>>     media
>>>>>     [RFC4566]
>>>>> recvonly
>>>>>     session,media,dcsa
>>>>> [RFC4566][RFC4975][draft-ietf-mmusic-msrp-usage-data-channel]
>>>>>
>>>>>
>>>>> (And this could also be extended for websockets if somebody 
>>>>> proposes a
>>>>> way to negotiate attributes for data channels too.)
>>>>>
>>>>> Using this format, if you want to know more than the name and the
>>>>> level(s) at which it can be used you need to consult the references.
>>>>> And when there are multiple references you don't know which one(s) 
>>>>> you
>>>>> need to consult. This can be "fixed" by including more information
>>>>> from the reference into the registry. Conversely, we could strip it
>>>>> down further and remove the levels from the registry - so you need to
>>>>> consult the references for that too.
>>>>>
>>>>> For instance, if we wanted to simplify finding the right reference 
>>>>> for
>>>>> the level you are interested in, we could do:
>>>>>
>>>>> *SDP Name*     *Level(s)*     *Reference(s)*
>>>>> accept-types
>>>>>     media,
>>>>> dcsa
>>>>>     [RFC4975]
>>>>> [draft-ietf-mmusic-msrp-usage-data-channel]
>>>>> cat
>>>>>     session
>>>>>     [RFC4566]
>>>>> fmtp
>>>>>     media,source     [RFC4566][RFC5576]
>>>>> mediaclk
>>>>>     session,media,source
>>>>>     [RFC7273]
>>>>> ptime
>>>>>     media
>>>>>     [RFC4566]
>>>>> recvonly
>>>>>     session,media,
>>>>> dcsa
>>>>>     [RFC4566][RFC4975]
>>>>> [draft-ietf-mmusic-msrp-usage-data-channel]
>>>>>
>>>>>
>>>>> Or we could go further, and break the dcsa level down by subprotocol:
>>>>>
>>>>> *SDP Name*     *Level(s)*     *Reference(s)*
>>>>> accept-types
>>>>>     media,
>>>>> dcsa(MSRP)
>>>>>     [RFC4975]
>>>>> [draft-ietf-mmusic-msrp-usage-data-channel]
>>>>> cat
>>>>>     session
>>>>>     [RFC4566]
>>>>> fmtp
>>>>>     media,source     [RFC4566][RFC5576]
>>>>> mediaclk
>>>>>     session,media,source
>>>>>     [RFC7273]
>>>>> ptime
>>>>>     media
>>>>>     [RFC4566]
>>>>> recvonly
>>>>>     session,media,
>>>>> dcsa(MSRP)
>>>>>     [RFC4566][RFC4975]
>>>>> [draft-ietf-mmusic-msrp-usage-data-channel]
>>>>>
>>>>>
>>>>> Thoughts?
>>>>>
>>>>>     Thanks,
>>>>>     Paul
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> mmusic mailing list
>>>>> mmusic@ietf.org
>>>>> https://www.ietf.org/mailman/listinfo/mmusic
>>>>
>>>>
>>>>
>>>> _______________________________________________
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>>>
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>>
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