[asterisk-bugs] [Asterisk 0013976]: Invalid SDP attributes for boolean T.38 parameters (T38FaxFillBitRemoval, etc.)

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
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http://bugs.digium.com/view.php?id=13976 
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Reported By:                linulin
Assigned To:                
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Project:                    Asterisk
Issue ID:                   13976
Category:                   Channels/chan_sip/T.38
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     new
Asterisk Version:           SVN 
SVN Branch (only for SVN checkouts, not tarball releases):  trunk 
SVN Revision (number only!): 158959 
Disclaimer on File?:        N/A 
Request Review:              
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Date Submitted:             2008-11-26 10:39 CST
Last Modified:              2008-12-23 13:13 CST
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Summary:                    Invalid SDP attributes for boolean T.38 parameters
(T38FaxFillBitRemoval, etc.)
Description: 
SDP part with enabled T38FaxFillBitRemoval, T38FaxTranscodingMMR, and
T38FaxTranscodingJBIG parameters must look like:

  a=T38FaxFillBitRemoval
  a=T38FaxTranscodingMMR
  a=T38FaxTranscodingJBIG

instead of:

  a=T38FaxFillBitRemoval:1
  a=T38FaxTranscodingMMR:1
  a=T38FaxTranscodingJBIG:1

SDP part with disabled T38FaxFillBitRemoval, T38FaxTranscodingMMR, and
T38FaxTranscodingJBIG parameters must be empty instead of:

  a=T38FaxFillBitRemoval:0
  a=T38FaxTranscodingMMR:0
  a=T38FaxTranscodingJBIG:0

Otherwise interoperability issues with other T.38 implementations are
likely to arise.

Quoting ITU-T Recommendation T.38:

Section “D.2.3.1 UDPTL and TCP negotiation”:

“Note that options without values are boolean – their presence
indicates that they are valid for the session.”

Section “D.2.3.2 RTP negotiation”:

Those parameters are supplied in a semi-colon separated list of
“parameter” or “parameter=value” pairs using the “a=fmtp”
parameter defined in SDP; the “parameter” form is used for boolean
values, where presence equals “true” and absence “false”.

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 (0096915) putnopvut (administrator) - 2008-12-23 13:13
 http://bugs.digium.com/view.php?id=13976#c96915 
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arcivanov: Thanks for all the patches.

I've taken a look at them, and all the _update patches look good by my
eyes. As far as the _relaxed patches go, I'm all for being able to accept
the non-standard T38 a parameters that the Gafachi uses, but I'm hesitant
about also adding those lines to our outgoing SDPs. I'll have to give it
some more thought. 

Issue History 
Date Modified    Username       Field                    Change               
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2008-12-23 13:13 putnopvut      Note Added: 0096915                          
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