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Token Ring Statistics
The first station detecting the data corruption sets the E bit to 1 in the ending
delimiter of the frame and logs the error. This prevents other stations from
logging the error and isolates the portion of the line which is causing the data
corruption.
Burst Errors
Displays the total number of burst errors detected on the ring. These errors occur
when a station does not clock an incoming data signal correctly.
Token ring protocol uses Differential Manchester Encoding for its signalling
format. Using this code, each bit time is halved, with a correct signal having a
transition at the center of the bit time (i.e., switching between 0 and 1, or vice
versa, in the middle of the bit time). Burst errors occur when a station receives five
half-bits of Manchester encoded data without a change in phase from 0 to 1 (thus
indicating no change in data value).
These usually occur when there was a brief disruption on the cable, or a brief
electrical surge or electronic noise on the network.
A.C. Errors
The count of AC Errors detected on the ring. These indicate that the reporting
station's Nearest Active Upstream Neighbor (NAUN) is faulty, because it is
unable to report its address during neighbor notification.
If a station receives more than one Active Monitor Present (AMP) or Standby
Monitor Present (SMP) frame with the Address Recognized Indicator (ARI) and
Frame Copied Indicator (FCI) bits set to 0 without receiving an intervening AMP
frame with these bits set to 1, it recognizes that its NAUN failed to set the
ARI/FCI bits.
The detecting station indicates the error to the active monitor, then ends the ring
poll process by not transmitting an SMP frame.
Abort Sequences
The count of abort delimiters transmitted on the ring. These are recorded when a
station detects a corrupted token while transmitting, then sends an abort
delimiter to halt frame transmission before the expected end-frame sequence.This
error will cause the active monitor to restore the ring through the ring purge
process. This error is somewhat uncommon, and often indicates 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 Errors
Displays the total number of internal errors detected on the ring. These are
recorded when a station recognizes a recoverable internal error in its own adapter.
You can use this to detect a station in marginal operating condition, possibly with
an inoperable chipset, timers, or counters. A large number of internal errors can
indicate that one or more stations on the monitored ring are in marginal operating
condition.
Network Level Statistics
3-7
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