Subject: [SIP] T.38 Attribute Negotiation

From: Bill Sulzen <[email-masked]>
Date: Wed, 14 Mar 2001 16:56:51 -0500

Jean-Francois,

I have a couple of questions concerning SDP negotiations you can
hopefully address. These are T.38-specific, but probably really fall
into the realm of general SDP questions. My problem is I don't
understand how SDP attribute negotiation is supposed to work. Or perhaps
I should restate
that by saying I want to do SDP negotiation (which SDP isn't supposed to
be used for) in the most interoperable way.

I'm a bit confused over how certain T.38 attributes are negotiated. In
particular, I the ones that specify a range (T38MaxBitRate,
T38FaxMaxBuffer and T38FaxMaxDatagram). For example, if a T.38 INVITE
contains the attribute T38MaxBitRate:14400, but the receiving device
only supports 9600, what should occur? Can the receiving device respond
with a 200 OK containing T38MaxBitRate:9600?

Do all the negotiated T.38 attributes need to be included in the 200 OK
for the case of a T.38 media stream replacing an audio stream?

Should a T.38 call be rejected based on a T.38 attribute negotiation
failure? For example, if the T.38 INVITE indicated UDP and localTCF,
should this be rejected?

Or what if the T.38 INVITE contained t38UDPRedundancy, but the recipient
does not support redundancy?

Thanks,
Bill

--
Bill Sulzen          email: [email-masked]
Office: 919-392-2514 epage: [email-masked]

---

From: Jean-Francois Mule <[email-masked]>
Date: Thu, 15 Mar 2001 10:40:37 -0800

This question is an implementation one;  the thread will be redirected
to the [email-masked]' list.  Look for the reply on
that list.
Jean-Francois.
> -----Original Message-----
> From: [email-masked]
> [mailto:[email-masked]]On Behalf Of Bill Sulzen
> Sent: Wednesday, March 14, 2001 1:57 PM
> To: Jean-Francois Mule
> Cc: [email-masked]
> Subject: [SIP] T.38 Attribute Negotiation
>
>
> Jean-Francois,

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