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--- controls:protocols:bacnet:qna [2020/10/02 10:04] – old revision restored (2020/09/30 02:55) 144.76.29.148
+++ controls:protocols:bacnet:qna [2020/10/03 19:23] – old revision restored (2020/09/30 16:24) 192.99.13.75
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-====== Questions / Answers ======
+====== BACnet Questions and Answers ======
 Here are a few interesting Q&A gathered from the BACnet mailing list.
-==== max_info_frames ====
+===== Broadcasts =====
+??? Can devices ignore Who-Is broadcasts?
+When sending a Who-Is broadcast, I have some devices that won't answer I-Am like I would expect them to.
+- Christian Fortin
+!!!
+(…) broadcasts can and will get lost, especially when there are a lot of them. If you broadcast a Who-Is with no parameters, ALL devices have to answer, so you will get a flurry of I-Am, some of which may get dropped.
+- John Hartman
+!!! See the related [[http://blog.hvac.io/2015/01/11/network-discovery-with-devices-ignoring-whois/|blog post]]
+??? Should a BACnet/IP router answer to global broadcast messages?
+New version of the Tridium Jace bacnet module, if configured to act as a bacnet/ip - MSTP router, will respond to "local" broadcast message (ex. 192.168.1.255)
+But not to Global broadcast messages (ex. 255.255.255.255)
+- Christian Tremblay
+!!!
+B/IP messages sent to 255.255.255.255 should be handled as normal BACnet broadcasts, as that address is reserved for broadcasting on the local subnet. So, these messages should be handled identically to messages sent to the broadcast address of the subnet.
+- Coleman
+===== max_info_frames =====
 ??? Can adjusting the max_info_frames increase overall network speed?
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 - John Hartman
+!!!
+To question 2)
+Devices not supporting READ-PROPERTY-MULTIPLE may significantly slow down the network.
+The reason is:
+- If multiple properties from the same device need to be polled by another deivce (controller or workstation) then individual READ-PROPERTY services need to be issued.
+The amount of extra tokens used when a workstation updates it's status depends on how many properties are read from single devices.
+- Christoph Zeller