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frame or token, and are commonly attributed to ring reconfiguration or a
possibly a faulty NIC.
• Type 3—Type 3 soft errors require the election of a new active monitor and
a ring-purge procedure. They are either a result of the loss of the ring's
active monitor, or result in loss of the active monitor.
The level of ring recovery associated with each soft error must also be distinguished.
In addition to being categorized as either an ISE or a NSE Token Ring soft error,
each Token Ring soft error is further classified as a Type 1, Type 2, or Type 3 error.
The following is a list describing the most common Token Ring soft errors (including
their classification and recovery type):
• Line error—An isolating, Type 1 error. It indicates that the frame has a CRC
error.
• Frame copy error—A non-isolating, Type 1 error. It indicates that a station
copied a frame with its source address.
• Multiple monitors—An isolating, Type 1 error. It indicates that the active
monitor received a ring-purge frame that it had not sent.
• Receiver congestion error—A non-isolating, Type 1 error. It indicates that a
station was unable to receive a frame that was addressed to its address.
• Burst error—An isolating, Type 2 error. It indicates that a signaling error
occurred. Burst errors are a common result of a station being added or
removed to the ring. Occurrences of burst errors when no reconfigurations
are occurring are often an indication of a cabling problem.
• Abort delimiter transmitted error—An isolating, Type 2 error. It indicates
that the ring station detected a corrupted token or some type of
unrecoverable internal error, which requires it to abort its transmission.
• Lost token error—An isolating, Type 2 error. It indicates that the active
monitor's "Any_Token" time expired. If the active monitor fails to detect a
token or frame once every 10usec, it purges the ring.
• Lost frame error—A non-isolating, Type 3 error. A lost frame error indicates
that a station has sent a frame and has not received it back. The error is
generated if the ring station (functioning as a standby monitor) fails to
receive a token once every 2.6 seconds. This is tracked locally by the station
with the Good_Token timer. An error is also genterated if the station is not
polled once every 15 seconds by the ring's active monitor (also tracked
locally with the Receive_Notfication timer).
• Frequency error—A non-isolating, Type 3 error. It indicates that a station
received a frame that is out of clock frequency with the rest of the ring. As
mentioned in Chapter 5, one of the functions of the active monitor is to
provide the ring's master clock for transmission timing. Token Ring uses a
line clock rate of 8MHz (for 4Mbps Token Ring) and 32MHz (for 16Mbps
Token Ring). Although the ring signal (maintained by the frame/token) is
retimed as the token is passed from station to station, due to signal
attenuation from the transmission medium and varying component