Global Who-Is requests are important to ensure all of the devices on your system are accounted for. However, if they occur too often they can clog the system with all of the I-Am replies. It is important to know if they are being sent out too frequently.
A great way to see if this is happening is by visualizing the traffic in your network. On the homescreen of Visual BACnet, you can see all of your network traffic, with BACnet traffic in green. In the image below, you can see that traffic is regularly spiking – a good clue that something is not quite right.
In this case, the Global Who-Is diagnostic check failed: there are 46 packets with Global Who-Is in this 20-minute capture. If you click on it, you can drill down to see more information about why it failed.
Upon further inspection, we can see that source device 00:11:22:03:12:ee is sending a Global Who-Is every minute.
In this case, a particular device was configured to “discover everything” every 60 seconds, in the form of Global Who-Is requests. This system is very large and the default configuration caused unexpected delays. Visual BACnet allowed this user to very quickly identify the source of the problem and fix it.