Statistics
If a station receives an AMP or SMP MAC frame with the ARI and FCI bits set to 0 without first receiving an intervening AMP frame it recognizes that its upstream station failed to set the ARI/FCI bits.
The receiving station will increment an ARI/FCI set error counter, and end the ring poll process by not transmitting an SMP MAC frame. Since it has not received a valid SMP frame, it does not have a correct NAUN address. However, stations between the Active Monitor and the malfunctioning adapter will have correct NAUN addresses.
This error will not cause ring recovery functions to occur. You will probably not witness this error often, since it is associated with a station hardware problem rather than a “normal” disruption of ring activity. However, if you do note that a station’s adapter did not increment the ARI/FCI bits, you might assume that the adapter is failing or about to fail. You can isolate this error to the upstream adapter of the reporting station.
Abort Error
These occur when an adapter has frames to transmit and receives a token, but does not detect an ending delimiter on the token after its access control field. This indicates that the token is corrupted.
This error will cause the Active Monitor to detect a lost token (since it was not released back onto the ring) and to restore the ring through the ring purge process. This error is also somewhat uncommon, and will often indicate a failing adapter. A common cause of abort sequences is overheating by the adapter in an overloaded system. Note that the adapter may also issue an Internal Error simultaneously, which will cause the adapter to remove itself from the ring.
Internal Error
An internal error is counted when a station recognizes a recoverable internal error in its own adapter (and may temporarily remove itself from the ring). A large number of internal errors can indicate that one or more stations on the monitored ring are in marginal operating condition.
Non-Isolating Errors
Lost Frames
A lost frame error is counted each time a station’s TRR (Timer, Return to Repeat) timer expires before the frame it is transmitting returns. This timer, which is set to
4.1milliseconds, ensures that each station issues a new token after having transmitted data.
Ring and Station Variables |
