RE: [AVT] Re: draft-jones-avt-audio-t38-04.txt

["Medhavi Bhatia" <mbhatia at nextone.com>]

I have a question regarding t.38. Is the following draft still work in
progress ?

draft-ietf-sipping-realtimefax-01.txt

Thanks,
Medhavi.

> -----Original Message-----
> From: avt-bounces at ietf.org [mailto:avt-bounces at ietf.org] On Behalf Of
Colin Perkins
> Sent: Wednesday, May 26, 2004 8:00 AM
> To: Magnus Westerlund
> Cc: Paul E. Jones; tamura at toda.ricoh.co.jp; avt at ietf.org; Mundra, Satish
> Subject: Re: [AVT] Re: draft-jones-avt-audio-t38-04.txt
> 
> On Wednesday 26 May 2004 12:42, Magnus Westerlund wrote:
> > Hi,
> >
> > As I understand it, the below SDP attributes are in fact only used when
> > the usage is with m= lines that looks like the following (using udptl or
> > tcp as protocol):
> >
> >  From section D.2.4.1 of T.38
> >
> > m=image 49170 udptl t38
> > a=T38FaxRateManagement:transferredTCF
> > a=T38FaxUdpEC:t38UDPFEC
> > m=image 49172 tcp t38
> > a=T38FaxRateManagement:localTCF
> 
> Agreed.
> 
> > While what we are now defining is the parameter that belongs to the T.38
> > RTP payload format. This new payload format should really use the
> > standard procedures for any m= line with RTP in it. Therefore you need
> > to follow the methods in RFC 3555 for this.
> 
> I agree in principle, but I'm not sure it's that simple in practise. If we
> use the RFC 3555 approach, and define MIME parameters with a mapping to
> "a=fmtp:", there is a difference between the signalling for T38-over-RTP
> and for T38-over-udptl. This makes implementations more complex, since
> they need to understand both sets of attributes if they support both RTP
> and udptl transport, and makes the specification more complex since it has
> to define the interaction.
> 
> Using "a=fmtp:" for the parameters to the RTP payload format is probably
> the right approach, but we should be aware of the issues.
> 
> Colin
> 
> _______________________________________________
> Audio/Video Transport Working Group
> avt at ietf.org
> https://www1.ietf.org/mailman/listinfo/avt


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