I understand the confusion. I think the issue is what kind of device you
are building. If you are building a T.38 relay then there is value to this
parameter.
Data is arriving at the receiving relay (relay operating its high speed
receiver)
at roughly the same rate it is being clocked out of the transmitting relay
(relay operating
its high speed transmitter). So the buffering at the other relay is really
irrelevant to the processing
at the receiving relay.
But, if you are building an internet fax machine or fax server that supports
T.38
There is no practical limit to the amount of data that can be generated. For
example
if a fax server is sending the contents of a file, the entire image is available
instantly.
It is the obligation of the receiving fax terminal to ensure that the data it
sends does not
get too far ahead of the transmitting relay. "Too far" is the value for
T38FaxMaxBuffer.
In our T.38 based fax server, we go to great lengths to ensure that the average
rate
of data emitted from the server is equal to the negotiated modem data rate. In
this
case we need not consider T38FaxMaxBuffer (and don't).
Cliff Schornak
CTO
Commetrex Corp.
"Attila Sipos" <[EMAIL PROTECTED]> on 03/20/2007 07:18:28 AM
To: [email protected]
cc: (bcc: Clifford J Schornak/Commetrex)
Subject: [Sip-implementors] T38FaxMaxBuffer
(Sorry if this is the wrong group to post to)
in draft-jones-avt-audio-t38-04.txt, they describe
T38FaxMaxBuffer:
T38FaxMaxBuffer: Indicates the maximum number of octets that can
be stored on the remote device before an overflow condition
occurs. It is the responsibility of the transmitting application
to limit the transfer rate to prevent an overflow. The negotiated
data rate should be used to determine the rate at which data is
being removed from the buffer. Value is an integer.
My problem is that I don't see how this value tells us anything.
e.g.
say the T38FaxMaxBuffer is 200
and say T38MaxRate is 14400
So at 14,400bps, we generate 1800 bytes/second.
Now it says:
>> The negotiated
>> data rate should be used to determine the rate at which data is
>> being removed from the buffer. Value is an integer.
So this means the data is being removed 9 times per second (1800/200).
So why is this important?
My thinking is that if we have the T38MaxRate parameter,
then how does T38FaxMaxBuffer tells us anything extra?
What are we supposed to do with this information?
Can someone explain how to use the T38FaxMaxBuffer parameter
when it is received?
Regards,
Attila
Attila Sipos
http://www.vegastream.com
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