Re: [hylafax-users] Hylafax comportation with high latency...

[Lee Howard <faxguy@xxxxxxxxxxxxxxxx>]

On 2004.09.16 10:01 Diego Ercolani wrote:
> Hallo,
> I would like to use hylafax with fastweb.
> Fastweb is a Telco Company that gives mainly internet data connection
> over
> fiberglass, but as a classic telco company permits to have a classic
> phone
> line FXO mapped on their apparates so you can connect a standard phone
> that
> is then converted in VOIP stream (they said that codec is u-law so
> lossless).
> The very annoying problem is that you can have a call with about 1
> second of
> latency. This (I think) would really decrease Hylafax reliability.
> What I have is that from the old installation of Hylafax where we had
> a
> classic copper phone pair, and hylafax did its work very well, now we
> are
> experiency the situation where transmit and receive faxes with hylafax
> is
> very difficult, many tryies and many requeues.
> Prartial transmits and partial receives.
> Reports from hylafax say only:
> Communication failure during Phase B/C
> But having a look to a session log runtime, it's possible to see that
> at some
> point transmission end while in a page and then after a timeout of
> 1min:20
> seconds, hylafax resumes its state.
> But stop transmission.
> The only difference was the line: before we have a copper line, after
> a
> fiberglass and VOIP.
> Could it be a problem of high latency?

In this case, no, it doesn't look like latency.

> I've tryied with a standard fax machine (hp multifunction printer) and
> all
> work well......

Your HylaFAX version is 4.1.8 and you're running in Class 2 (I think, 
whatever AT#CLS=2 does on your modem).  So comparing it against an HP 
multifunction device really isn't a fair comparison.  The HP likely has 
a better fax implementation than does your modem's Class 2 firmware.  
Also, the the HP likely supports ECM (error correction), which is going 
to make it "look" like there are no problems due to the end result.

When faxing over VoIP you should certainly make sure to use ECM 
whenever possible.  In order to do this, upgrade to 4.2.0 and switch to 
Class 1.

> How can hylafax help me?
> For convenience I've included a sample log. Note that at about
> 17:49:38 modem
> stop writing data:
> Sep 16 17:49:38.89: [ 4976]: <-- data [1026]
> and then hylafax resumes with error:
> Sep 16 17:50:58.88: [ 4976]: MODEM TIMEOUT: writing to modem
> Sep 16 17:50:58.88: [ 4976]: MODEM WRITE SHORT: sent 1026, wrote 817
> Sep 16 17:50:58.88: [ 4976]: SENT 22472 bytes of data
> Sep 16 17:50:58.88: [ 4976]: SEND abort data transfer

This error indicates that the modem hardware or the modem driver was a 
problem in this case: it stopped accepting data from HylaFAX.

Lee.

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