Re: [hylafax-users] What happens to faxes that fail the PercentGoodLines test?

[Lee Howard <faxguy@deanox.com>]

On 2002.04.02 23:14 Dustin Puryear wrote:
> At 10:53 PM 4/2/2002 -0800, you wrote:
>>> I realize there is an obvious trade-off here.
>> 
>> If there is a problem with HylaFAX it is that it expects the sender's 
>> fax to make use of RTN, so it deletes the corrupt page and expects a 
>> replacement to come.  The problem with that assumption is that some 
>> senders out there don't make use of our RTN signal.
> 
> So it is possible that Hylafax will delete a corrupt page and the sender 
> will never know?

Yes.  If their system doesn't look for, handle, or hear (for whatever 
reason) our RTN signal, then the remote will likely just hang up, believe 
that we got the fax just fine, and faxgetty would have deleted the 
corrupted page already.  From what I know, faxgetty isn't expecting this 
behavior, so there's no way to tell faxgetty, "wait until they start page 
re-transmission before deleting the corrupted page".  I'd venture to guess 
that this was designed like this on purpose to avoid timing problems.

> Taking this to the worst case, if a one page fax is sent then we could 
> miss the entire fax and the sender wouldn't be aware of this?

Correct.  FaxMaster will know, though, that the fax was attempted and 
failed, and can probably judge from the TSI where it was coming from.

> Does this happen even if the receiving fax were a stand-alone machine 
> rather than Hylafax?

Yes, sometimes.  That depends on the system.  Worse are the fax machines 
that don't do *any* copy quality checking and have no capability to send 
RTN at all.  These machines will often get totally illegible pages with no 
recourse.

Cover sheets are important (and widely used) for this reason.  Faxing is 
not a 100% trustworthy delivery mechanism.  RTN is designed to assist in 
delivery success.  If a sender wants to ignore T.30's redundancy checks, 
then no equipment can compensate for it.

> Basically, if the sending fax machine ignores RTN then shame on them?

Pretty much.  If they're not going to pay attention to our 
acceptance/rejection of the image quality, then they should expect to have 
sending problems.  Except for possibly delivering a corrupted image to 
FaxMaster, I don't know what more can be done on our side.  Most of the 
times these corrupted pages would be so badly distorted that they would be 
unusable, anyway.

Lee.

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