Explains what FCS error hysteresis thresholds are and describes how they help prevent unnecessary alarm notifications due to brief bit error rate fluctuations in Ethernet switches.
The FCS error hysteresis threshold in Ethernet switches helps manage alarm notifications related to bit error rates. Understanding this threshold helps network administrators prevent unnecessary alarms caused by brief bit error rate fluctuations, resulting in a more stable network monitoring environment.
Bit-error rate (BER): Ethernet standards specify a maximum bit-error rate of 10⁻⁸, with a practical range between 10⁻⁶ and 10⁻¹¹.
FCS bit error rate: To configure the bit error rate for a switch, enter the exponent corresponding to your desired value (for 10⁻⁹, enter 9). The default value is 10⁻⁸.
The FCS error hysteresis threshold determines how a switch responds to changing bit error rates. If minor, brief increases in bit error rates occur, the hysteresis threshold prevents immediate alarm toggling (“alarm fatigue”). The threshold is expressed as the ratio of the alarm clear threshold to the alarm set threshold, measured as a percentage and can be set from 1 percent to 10 percent (default is 10 percent).
For instance, suppose the FCS bit error rate alarm is set to 10⁻⁸ (alarm set threshold) and the alarm clear threshold is set to 5 × 10⁻¹⁰. The hysteresis value (h) is calculated as: h = alarm clear threshold / alarm set threshold
h = 5 × 10⁻¹⁰ / 10⁻⁸ = 5 × 10⁻² = 0.05 = 5 percent
The FCS hysteresis threshold applies across all ports on the switch. By adjusting the hysteresis threshold appropriately, you can enhance monitoring accuracy and reduce alarm fatigue for more effective network management. For more information, see Configuring the FCS Bit Error Rate Alarm.