Re: [hylafax-users] COMREC Recieved DCN

[Lee Howard <faxguy@xxxxxxxxxxxxxxxx>]

On 2004.12.20 12:49 Stephen Carville wrote:

> Fair enough,  Can you tell me what to look for to determine that the
> connection is at fault?

In the logs you look at how many times PPR appears in an ECM-enabled 
fax.  Ideally PPR should never appear.  Of course, the reality is that 
on analog lines PPR will occur regularly, but hopefully not on most 
sessions.  When PPR does appear, it should be considered normal, but 
the number of image data frames that must be retransmitted after the 
PPR signal should indicate the degree of the problem.  Less than 10% of 
the original number of frames would be "tolerable" in my opinion.  If 
you start seeing more than 10 frames for every hundred needing to be 
retranmsitted, then there is a problem that should be addressed.

The PPRs occur because the image data "frame check" fails, meaning that 
HylaFAX knows the image data contained within the frame is corrupt.  It 
is done with a mathematical CRC against the data within the frame.  
Sometimes HylaFAX is able to determine that the data within a frame is 
corrupt without checking the CRC because the framing structure itself 
is either corrupt or indicates an incorrectly sized frame.

Lee.

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