BER testing from router using ping.

[cheriton]

I have had a problem whereby I ber tested a leased line to a remote loop & it worked fine with most test patterns.However certain test patterns produced errors.The problem was eventually solved when the PTT replaced a section of the leased line that was a radio link.I would have thought that a physical layer problem would have caused errors no matter what the test pattern was.
Can anyone explain this?

 

[Mikestudent]

I think your physical layer was configured so it could make problems for some data patterns. I'm quite sure you had problems with long patterns (2^20, QRSS, etc) and it was all right with short patterns. Inside these long patterns there are intervals with exessive numbers of zeros. In some cases for (AMI coding for example) it causes clock recovery problems and as a result ber-test errors.

Mike