Re: [MMUSIC] draft-holmberg-mmusic-t140-usage-data-channel - language indication

[Christer Holmberg <[e-mail]>]

Hi Gunnar,

12. At the end of 3.2, add the following about language negotiation

...

>>> I don't think we need to say anything how to specify. draft-data-channel-sdpneg defines how to convey
>>> SDP attributes in the dsca attribute, and 8873 defines the format of the hdland-send/recv attributes.
>>> We could include an example instead.
>> Yes.
>    
>    Proposal:
>    
>    Change 3.3. header from Example to Examples
>    
>    Add at the end of 3.3 the following:
>  
>
>    Another example is an offer for a T.140 data channel from an 
>    organisation offering real-time text conversation in Spanish and 
>    Esperanto, and an answer accepting Esperanto.
>    
>    Offer:
>    
>      m=application 911 UDP/DTLS/SCTP webrtc-datachannel
>            c=IN IP6 2001:db8::3
>            a=max-message-size:1000
>            a=sctp-port 5000
>            a=dcmap:1 label="ACME customer service";subprotocol="t140"
>            a=dcsa:1 fmtp:-
>            a=dsca:1 hlang-send:es eo
>            a=dsca:1 hlang-recv:es eo
>    
>    Answer:
>    
>    m=application 911 UDP/DTLS/SCTP webrtc-datachannel
>            c=IN IP6 2001:db8::3
>            a=max-message-size:1000
>            a=sctp-port 5000
>            a=dcmap:1 label="ACME customer service";subprotocol="t140"
>            a=dcsa:1 fmtp:-
>            a=dsca:1 hlang-send:eo
>            a=dsca:1 hlang-recv:eo
>    
>    (Christer, can you please insert the variations needed in the answer to 
>    make it a realistic example of offer - answer.)
  
If we want to keep it realistic, should we really use Esperanto? :)

One of my teachers in high school was a big fan of Esperanto, and claimed that it will take over English as the number one world language. But, that was only 30 years ago, so I guess there is still time :)

---

12a: Allow use of hlang- attributes together with m=application media declarations
    
... 

>>>> The problem is that we are not defining usage of the lang attributes, and modality, for the 'application/webrtc-datachannel' media type:
>>>> we are defining modality and usage of the attributes for a specific data channel.
>>>>
>>>> So, maybe something like:
>>>>
>>>>        "This document updates RFC 8373, by defining how the SDP hlang-send and hlang-recv attributes are used for
>>>>          the "application/webrtc-datachannel" media type.
>>>>
>>>>         SDP endpoints MUST NOT include the attributes directly in the m= section associated with the
>>>>         'application/webrtc-datachannel' media type. Instead, the attributes MUST be associated with
>>>>         individual data channels, using the  SDP dcsa attribute. A specification that defines a subprotocol
>>>>         that uses the attributes MUST specify the modality for that subprotocol.
>>>>
>>>>         For T.140 data channels the modality is 'written'."
>>>     
>>>     This works for the T140 data channel, but another subprotocol may be
>>>     able to carry more than one media type and therefore have some other
>>>     indication of what media type is used. An example is the msrp data
>>>     channel that can carry messages with different modalities. 
>>    
>> Sure, and the text says that each subprotocol specification need to define what the modality is.
>>
>> (Of course, it would have been great if 8373 would have defined a way to explicitly indicate the modality, instead of implicitly retrieve it from the media type.)
>
> Agreed. It was discussed but not included in the final result.

I think anything "implicit" should be forbidden in IETF standards - it always creates problems sooner or later....

 >>>     So, yes, it is tempting to say that we extend RFC 8373 in general, but
 >>>     we can do in in a fully specified way only for the T140 data channel.
 >>>     
 >>>     How would you express that?
 >> Using the suggested text above :)
 >>
 >> - It updates 8373 by allowing usage of the lang attributes for application/webrtc-datachannel media types.
 >> - It updates draft-data-channel-sdpneg, by indicating that the modality must be defined for each data channel that
 >>    uses the lang attributes. In draft-t140-data-channel we then define the modality for T.140 data channels.
 >   
 >   Yes, I agree, it can be read your way.
 >   
 >   But I read "A specification that defines a subprotocol that uses the 
 >   attributes MUST specify the modality for that subprotocol." as if only 
 >   one modality was tied to a specific subprotocol identity.
 >   
 >   Can we change the sentence to "A specification that defines a 
 >   subprotocol that uses the attributes MUST specify how the modality is 
 >   deducted for languages used with that subprotocol."
   
 Will fix.

 Regards,

 Christer

 
    
    Regards
    
    Gunnar
    
    >
    > Regards,
    >
    > Christer
    >
    >   
    >
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    -- 
    -----------------------------------------
    Gunnar Hellström
    Omnitor
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