Rx Frame Count greater than Tx Frame Count The greater the difference, the higher the
probability of the following conditions.
l One or more devices somewhere in BACnet internetwork is sending a lot of broadcast
messages.
l One or more devices on the router’s MS/TP network is sending a lot of network unicast
messages.
Typically a device is trying to find other devices that do not exist or are not communicating
properly and are repeatedly sending BACnet WHO-IS messages. Usually this is caused by a
Control Basic program or a Notification Class object recipient list referring to a device that
does not exist.
Rx Frame Count much less than Tx Count Will probably also see a device in a gray offline
status. It usually means devices are not communicating reliably either because of noise or
they because they are inundated with network messages and cannot keep up.
Tx Data Count This is the number of messages that contain actual point data. Most other
messages are just passing the token. In the previous example, the Data Count is only 0.1%
of the Tx Frame Count which just means the network is passing a small number of points or
trends. If this ratio is more than 30%, it may indicate a problem because it is likely that one or
more devices or workstation are gathering more data than is really needed. This can mean
the network will drop important messages.
Token Retry or Token Timeout This usually indicates a problem with the device next to the
router in the MAC chain. The cause could be noise specific to the device or general network
noise. This is not a problem unless this count is more than ten counts in a 24-hour period.
Rx PFM Count This indicates a problem between the router and the device just before it in
the MAC chain, usually the one at the end. A few counts in a 24-hour period is not unusual.
All other metrics Other metrics typically do not indicate a problem unless a value exceeds
ten counts in a 24-hour period. If you encounter issues, see the topic If you encounter
difficulty on page 12 to contact technical support.
BAC-5051E Router Section 4: Diagnostics and status
Revision J 47
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