Subject: 28. Why do I see lots of CRC errors? Why is my line so slow?

    
> "Make sure that the phone company uses gas or solid state lightning
> arrestors and not carbon arrestors on your circuit".  This is a problem
> which I see all too often: installers use a carbon arrestor either by
> accident, because it's all they had at hand, or because that's what was
> already on the pair assigned to the circuit.  Carbon arrestors introduce
> too much noise and should not be used on data circuits of any kind.
> On one ISDN line I had with carbon arrestors installed at both the CO
> and POP, I saw anywhere from 5 to 80 CRC errors per B channel per minute.
> Sync was frequently lost.  Once the carbon arrestors were replaced with
> gas arrestors, the error rate went down to 2 - 4 CRC errors per B channel
> per day.  As the CRC error rate increases, the performance of any
> protocol will begin to decline.  This is particularly a problem with
> protocols that do not handle packet loss well.  For instance, at error
> rates of 15+ CRC errors per minute (per B channel), I saw a significant
> loss of performance with AppleTalk.