Hi All,
I have few questions related to T.38 support in SIP.
I'll be thankful even if you can answer some of them.
Q1. In SDP, Is it possible to have following
attributes at the same time
a=T38FaxUdpEC:t38UDPFEC
a=T38FaxUdpEC:t38UDPRedundancy
As examples in draft-ietf-sipping-realtimefax-01.txt shows so,
while at the
same time
table in "7. SDP Attribute Table for T.38 sessions" shows
either of these
can be present but
not both.
Q2a. In SDP, is it possible to have both
a=T38FaxTranscodingMMR
a=T38FaxTranscodingJBIG ?
I think both can be present only with ":0" and not ":1"..
Is that true?
Q2b. Same draft says these are boolean and "true if
present" then
what is the use of ":0" and
"1"?
Q2c. Is it mandatory to append ":0" or ":1" for these
attributes?
Q3a.Is it required to support RFC2833 for supporting T38? Specially
when the
audio call is
established with a codec other
than "0" before switching to fax call?
Q3b. Do all the fax machines/gateways establish the audio call with
codec
"0" only ( as shown in the examples of
draft-ietf-sipping-realtimefax-01.txt
and
draft-mule-sip-t38callflows-00.txt)?
Q4a. What are the minimum and maximum values of
T38FaxRateManagement?
Q4b. Are these the only values for T38FaxRateManagement ?
2400,4800,7200,9600,12000 and 14400
Q5. Is their any sdp attribute something like
"transmitpower" for fax
calls?
Q6. What are the latest draft/RFC to refer for T38 suport in SIP
apart from
T.38 ITU specification?
Thanks and Regards,
Sushil Kumar
Axes Technologies (I) Pvt. Ltd.
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