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Re: [hylafax-users] COMREC Recieved DCN



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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