Re: flexfax: Re: Hylafax question

[Dmitry Bely <dbely@mail.ru>]

Dave Wreski <dave@nic.com> writes:

> > >I see from your post to the Hylafax list (below) that you
> > >have used Hylafax with 30 modems.  I am helping someone who
> > 
> > In fact we have 45 modems connected now !!
> 
> Wow, what model modem are you using? ;)
> 
> > The version we're using now is v4.1 with some additional patches
> > (mainly for the RTN problem). As we have the system running smoothly
> 
> Can you explain what the RTN problem is?

The receiving side can do some copy quality checking, e.g. count
single/consecutive bad scan lines etc. And RTN normally means unreadable
page -- percent of broken data on the receiving side has exceeeded some
threshold values (due to the noise during trasmission). Having RTN, the
sender has to perform the retrain and then (according to T.30) *can*
retransmit the page. But the problem is that many fax machines (e.g. Canon) 
also respond with RTN in case of some unobvious conditions, including
incorrectly generated fax data (due to bugs in the sending software). If
such software (e.g. Hylafax) retransmits the page after RTN over and over
again, you will just get unfamous "endless RTN" bug.

So I fixed both issues:
- eliminated the bugs, that led to incorrect fax T.4 data (byte-aligned
first EOL, extra RTC, etc.)
- added the RTNHandlingMethod option, allowing you to select more robust
method of handling RTN ("giveup" or "ignore" besides default "retransmit")

Hope to hear from you soon,
Dmitry