Re: [hylafax-users] High Error rates

[Lee Howard <faxguy@xxxxxxxxxxxxxxxx>]

On 2004.07.29 13:57 Aidan Van Dyk wrote:
> * Lee Howard <faxguy@xxxxxxxxxxxxxxxx> [040729 16:08]:
>
> > Normally we can work around most fax machines misbehaviors in Class
> 1
> > (Class 2 is up to the modem manufacturer).  However, when acting as
> the
> > receiver and we have received a corrupted page and the sender is
> > awaiting a response to it's post-page signal, we have limited
> choices:
> > MCF (confirm receipt), RTN (reject page, request retrain and
> > retransmit), DCN (disconnect), or hang up.  Confirming bad pages
> (doing
> > MCF) would be the worst mistake we could do.  Hanging up or
> > disconnecting would probably get the idea across, but at least
> sending
> > RTN will permit a spec-following intelligent sender to cope.
>
> Just a small poing:
>
> RTN:  Request retrain, Negative on page received
> RTP:  Request retrain, Positive on page received

:-)  I just grepped through a month's worth of logs to discover (to my 
amazement) that there were actually two instances (out of about 3000) 
where my sender received an RTP signal.  Interestingly, (and what 
amazes me in particular) is that RTP came as a response to EOP in both 
cases.  So the receiver was confirming the page as received, and it 
knew the page was the last page, so why did it request a retrain?

> The spec says nothing about a "retransmit requested" right away.

This is correct, and this is why there is so much variance in how RTN 
is handled.  The specification defines the RTN signal to mean that the 
page was not received properly, but it does not directly offer any 
suggestions as to how it should be handled (e.g. if the page should be 
retransmitted).  The flow charts in the older versions of the 
recommendation do suggest that the sender "go to the beginning of phase 
B", but this is by no means followed universally, and what the sender 
chooses to do once back at phase B is anybody's guess.

> Personally, I think the way HylaFAX handles it by default
> (RTNHandling:
> retransmit) is the intelligent option.  But I think most non-HylaFAX
> driver fax stuff out ther is probably more in line wiht the "ignore"
> HylaFAX handling, and you just get a little something somewhere
> (which most people would never know about, notice, or see) saying a
> particular page was not confirmed.

Which is a real shame, I think, if it happens much.  (I've not really 
had hands-on use with an actual fax machine for... uh... more than 5 
years now.  I look at them in the second-hand stores sometimes and 
think of how fun it would be to discover all of the bugs in it, but 
then I think "why?"  I guess I could use it as a desktop sheet-fed 
scanner if it is small enough.)

> If your fax is missing a page, you best call them up and get them to
> re-send it...  At least until we get all the world running HylaFAX ;-)

Ah, world dominion.  :-)

Lee.

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