Re: flexfax: Endless RTN -- seems to be fixed now!

[d1swdev <d1swdev@asiaonline.net>]

Hi Dmitry,

I'm writing to tell you that your patches do not fix my RTN problem.

I'm using ZyXel U336RE modem cards for my HylasFax server. I also have RTN
problem (but to a certain destination only). Before, I use the reduce speed
method
(forcing HylaFax to use modem speed 4800 instead of the modem capabled
14400) to fix the problem. But the problem still cannot be solved completely,
still about 30% of the FAX jobs will have RTN errors. These days, I tried
you patches but errors still occur.

Dmitry Bely wrote:

> I am glad to inform you that after a couple of days of hard work I have
> found a bug which caused infamous "endless RTN" problem. There is nothing
> special - Hylafax just violated T.4/T.class2 protocol specs :-)
>
> To be more specific, T.4/T.class2 (Class 2.0 standard) defines the
> following format for the Phase C data (core of G3 fax protocol):
>
> <EOL>
> <1-st encoded raw>
> <EOL>
> <2-nd encoded raw>
> <EOL>
> ...
> <last encoded raw>
> <RTC>
> <DLE><EOP>
>
> But Hylafax generates:
>
> <EOL>             \
> <1-st encoded raw> \
> <EOL>               \
> <2-nd encoded raw>   \ from Hylafax-generated g3 TIFF contains it
> <EOL>                /
> ...                 /
> <last encoded raw> /
> <RTC>             /
> <RTC>             -- sendRTC()
> <DLE><EOP>
>
> (not always -- just when no chopping happened. See the attached patches for
> details).
>
> As you can see, RTC is transmitted twice, and it may cause missing of the
> RTC/EOP and generating RTN/other transmission errors by the remote fax
> machine. Endless RTN (and possibly other unidentified errors) is here.
>
> Well, the attached patches seems to fix that. They are still experimental
> and possibly incomplete, but they work for me (tested with Zyxel 1496E in
> Class 2.0 mode).  A Panasonic BX780 fax machine, connected to the server
> via PBX, i.e. directly, now successfully generates MCF (always responded
> with RTN before). Could you, folks, check if they work for you also.
>
> Any comments are always welcome,
>
> Hope to hear from you soon,
> Dmitry
>
> P.S. I am also going to publish tsi processing bug fixes (after some
> testing). Stay tuned :-)
>

Anyway, I would like to say thank you for your efforts in trying to
solve the problem.

--
K.S.Wat
SSA(D)12
Computer Division,
Hong Kong Observatory.