A notification sent when we receive a PDU with a different value for the System ID Length. This notification includes an index to identify the circuit where we saw the PDU and the header of the PDU, which may help a network manager identify the source of the confusion. The agent must throttle the generation of consecutive isisIDLenMismatch notifications so that there is at least a 5-second gap between notifications of this type. When notifications are throttled, they are dropped, not queued for sending at a future time.