Subject: [Slim] Issue 21

From: Bernard Aboba <[email-masked]>
Date: Tue, 25 Oct 2016 10:51:14 -0700

In Issue 21, Gunnar suggests adding support for "text message" modality:
https://trac.tools.ietf.org/wg/slim/trac/ticket/21

There is a modality that we have not discussed at all yet. That is the
"text message" modality. It is not really interactive, but very often used
together with interactive media in a kind of slow pseudo-conversational
mode. One implementation is MSRP that is specified by the m=message media.
There seems to be some interest to extend our specification to handle that
modality as well.

Then the text message modality needs to be described and how it is
implicitly identified in sdp both in the main media m=message and in a
subchannel of a data channel.

[BA] Would it be sufficient to add an m=message example to Section 6.5?

Looking at https://tools.ietf.org/html/draft-ietf-mmusic-data-channel-sdpneg
I am concerned about the potential complexity of allowing language
negotiation at the subchannel level.  Is this really necessary?

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From: Gunnar Hellström <[email-masked]>
Date: Mon, 31 Oct 2016 20:09:26 +0100

Den 2016-10-25 kl. 19:51, skrev Bernard Aboba:
> "text message" modality. It is not really interactive, but very often 
> used together with interactive media in a kind of slow 
> pseudo-conversational mode. One implementation is MSRP that is 
> specified by the m=message media. There seems to be some interest to 
> extend our specification to handle that modality as well.
>
This is tricky, and I don't know what to propose. m=message can be used 
for all kinds of media in message communication. But it is text 
messaging that is realistic to use in a kind of pseudo - conversational 
mode. It does not look really clean to just add a language attribute the 
media specification and assume that it shall be understood as a 
specification to use text messaging for pseudo-conversational mode with 
text messaging.
I regret I proposed it late in the process.  I think it should be 
withdrawn.
>
> Looking at 
> https://tools.ietf.org/html/draft-ietf-mmusic-data-channel-sdpneg I am 
> concerned about the potential complexity of allowing language 
Yes. it is needed for real-time text in WebRTC.  But luckily the syntax 
is defined. It is proposed to be included in the draft by issue #9.  It 
must be specified on subchannel level, because that is where the 
specific streams used for the different modalities are transported.
The fact that language and modality negotiation in this way can be 
introduced in webRTC is the reason why I have stopped arguing for using 
the RFC 3480 / 3841 SIP language tag mechanism. So we should rather 
agree on what is needed to indicate how the usage in a subchannel of 
WebRTC data channel shall be specified. #9 has a proposal, but I am not 
totally sure that it is sufficient.

Gunnar
>
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Gunnar Hellström
Omnitor
[email-masked]
+46 708 204 288