Subject: [SIP] SIP T.38 negotiation failure and G.711 upspeeding

From: Bill Sulzen <[email-masked]>
Date: Thu, 08 Mar 2001 11:38:58 -0500

Jean-Francois,

Section 6.2 of draft-mule-sip-t38callflows-01.txt addresses upspeeding
to G.711 in the event of T.38 negotiation failure. This is great!
However, it woud be desirable to exchange additional information.
Typically for modem or fax passthru over the audio codec, it is
desirable to perform additional steps such as disabling VAD and perhaps
echo cancellation. Ideally, this would be signalled thru the SDP as
well. How might this be addressed?

Thanks,
Bill

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---

From: Jean-Francois Mule <[email-masked]>
Date: Thu, 8 Mar 2001 11:45:25 -0800

> to G.711 in the event of T.38 negotiation failure. This is great!
Thank you for the comments.

> well. How might this be addressed?
I agree and had started to look seriously into this - see email exchange
below.
My conclusions to date leads to the following proposal:
  -> create a separate I-D to discuss those 2 media attributes which
have a broader applicability than just ATM (silenceSupp and ecan); this
I-D would just be a way to get additional comments on silence supp /
echo cancellation;
  -> get IANA to properly register those
  -> update draft-ietf-mmusic-sdp-atm-05.txt
  -> update the T.38 sip draft accordingly

Agree? Any comments on this base proposal?
Jean-Francois.

-----Original Message-----
From: Jean-Francois Mule [mailto:[email-masked]]
Sent: Sunday, March 04, 2001 1:35 PM
To: [email-masked]'; [email-masked]'; [email-masked]'
Cc: 'Tom-PT Taylor'; [email-masked]'; [email-masked]';
[email-masked]'; 'Jieying Li'
Subject: SDP Media attributes: looking for references for echo
cancellation/silence suppression

Dear MMUSIC wg chairs:
It is my understanding that the media attributes described in
draft-ietf-mmusic-sdp-atm-05.txt for silence suppression and echo
cancellation are applicable to other transports than ATM.

Can you provide me with an existing reference of the IANA assignments
for these?
If there is not (and I have not seen one apart from the I-D mentioned
above which couples those with ATM transport), is there any interest in
documenting those?

An option could be to:
 - start a new I-D for those media attributes, as a way to request
comments,
 - remove the definition of those attributes in the next rev of ID
sdp-atm (& reference the new ID)
=> this will allow discussions on this specific topic and should lead to
proper IANA registration of those.

Any guidance or comments you may provide would be appreciated.
Regards,
Jean-Francois Mule.
Clarent Corporation

-----Original Message-----
From: Tom-PT Taylor [mailto:[email-masked]]
Sent: Saturday, March 03, 2001 9:23 PM
To: Jean-Francois Mule
Cc: Jieying Li; [email-masked]; [email-masked]; [email-masked]
Subject: RE: SDP Media attributes: looking for references for echo
cancell ation/no silence suppression

You can view IANA aassignments at
ftp://ftp.isi.edu/in-notes/iana/assignments/
Look under media types, or something like that.  Unfortunately, I'm not
sure you'll find what you need there.

The ATM-SDP attributes you cite may or may not be reusable for other
transports.  I'm not sure how tightly they are coupled with the ATM/AVP
profile.

For general consultation try the MMUSIC chairs, Joerg Ott <[email-masked]>
for one.

-----Original Message-----
From: Jean-Francois Mule [mailto:[email-masked]]
Sent: Tuesday, February 27, 2001 6:16 PM
To: [email-masked]'; 'Tom-PT Taylor'; [email-masked]';
[email-masked]'
Cc: 'Jieying Li'
Subject: SDP Media attributes: looking for references for echo
cancellation/no silence suppression

After some research, I still can't determine if there is an ultimate
reference document or an IANA registration specifying how to indicate
common codec options in SDP media attributes.  I am mostly interested in
echo cancellation/silence suppression.  The browsing of the 13 meg
MMUSIC archive leads to a couple of threads involving the recipients of
this email but it does not lead to a clear pointer.

In draft-ietf-mmusic-sdp-atm-05.txt, the following attributes are
described:
        * The 'silenceSupp' attribute, used to indicate the use of
          of voice activity detection for silence suppression, and to
          optionally parameterize the silence suppression function.
        ...
        * The 'ecan'  attribute, used to indicate the use of
          of echo cancellation, and to parameterize this function.

Can you confirm those options are the right ones?
(draft-ietf-mmusic-sdp-atm-03.txt had 'ecanf' as an attribute...).
Does anyone have any pointer to the "ultimate reference"?
Where can we browse through the existing IANA registrations for SDP
attributes?

Thank you very much in advance,
Jean-Francois Mule'
Clarent Corporation.