With a digital card, you may encounter the following CLI message from time to time:
PRI got event: HDLC Abort (6) on Primary D-channel of span X
The HDLC Abort(6) message is actually not an error (or even a warning). It is a notice message generated by Asterisk, indicating that a frame on the span failed a consistency check and is being discarded or ignored.
An abort is generated when seven 1's appear consecutively within a frame. HDLC is written so that any sequence of five 1's automatically has a zero inserted after it as a delimiter. This is necessary because the flags to start and end a frame consist of bytes that look like this:
01111110 (six 1's with a zero at each end)
Also, if the line is idle, bytes consisting of all ones are sent. So whenever the actual data being carried contains more than 5 ones consecutively it must be coded to not conflict with the flag or idle frames. An abort generally occurs when there is data corruption and this "no more than 5 ones in a row" rule is broken. The data corruption can be caused by several different things; it could be a problem on the telco equipment, or a faulty PRI cable, a problem with the T1/E1 card, or a hardware issue internal to the server itself.
It is not uncommon to see some HDLC Abort(6) messages on a perfectly normal PRI connection from time to time. The only time to be concerned about this message is if you see a lot of them, or if they appear to stream constantly to the CLI or Asterisk log.
If you are seeing this, one of the first things to check is the cable. Try swapping the PRI cable out with another one, to make sure that it's not a defective cable or connector.
You may also want to try running a loopback test on the card. Please see this KB article for information on this:
If there are still problems, please contact Digium Technical Support, or open a support case through your user portal at digium.com