Subject: Re: AW: [AVT] Working group last call: draft-ietf-avt-rtp-clearmode-02.txt - random comments

From: Tom Taylor <[email-masked]>
Date: Fri, 19 Sep 2003 14:51:39 -0400

The 56 kbit/s usage happens in North America because the low-order bits on 
occasional frames are stolen for signalling.  I would suggest that CLEARMODE ignore 
the issue.  The gateways can sort out the situation based on signalling passed 
between them.

Kreuter Ruediger wrote:

> Thanks for your comments
> 1 and 3 is simple (see below),
> but the 2nd one needs some discussion in the working group (see below)
>  
> Regards,
> Ruediger
> 
...
> 
> 	
> 	- Are 56kbps ISDN connections specifically excluded from this draft?  It seems to imply that you can use the 64kbps for anything you want as long as use use all 64kbps.  Would it be useful to indicate that lower rate data + padding can be passed by mutual agreement, or will that just blow up into a whole mess about how to define mutual agreement. 
> 
> 	Ruediger: Well !
> 
> 	- I would like to here a comment from the US members in the working group. Is it necessary to support 56kbps, 48kbps, ... at all ? These bitrates are not supported in RFC 3551 for PCMA/PCMU.
> 
> 	- Are there other applications that need a 56 kbps (or lower) channel ?
> 
> 	- If necessary, is the use of fill bits the appropriate method ?
> 
> 	- Would we start to conflict here with the N x 64 kbps work in PWE3 ?
> 
> 	- If support of "64 - (N x 8; where 1 <= N <= ?) kbps" is necessary and should be supported by the Clearmode draft, then we have at least two possibilities:
> 
> 	1) different MIME subtypes for each bitrate (e.g. Clearmode-64, Clearmode-56, etc.), as e.g. with G.726 in RFC3551
> 
> 	2) introduction of an optional bitrate parameter (in kbps), with "64" as default  -> this should be synchronized with the N x 64 kbps work in PWE3  
> 
> 	BTW: I am not a member of the PWE3 discussion list. Any answer of PWE3 members should be sent to [email-masked] too.
> 
> 	 
> 
> 	
> 	- Would it be useful to define where the most and least signficant bits are for each sample, or is that already defined in one of the references? 
> 
> 	Ruediger: this makes sense; I will copy the regarding sentence from RFC3551, chapter 4.5.14 (RTP Profile for PCMA/PCMU)
> 
> 	 
> 
> b#bu୩즊Z
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