The ideal capture length for Visual BACnet

The optimal capture length will be dependent on the intended use of the pcap file.

To get a general system health check — perhaps after commissioning, before starting a job, or for regular audits — we recommend a minimum of a one-hour capture. A 24-hour capture can be very helpful towards understanding network health throughout the day, and can capture changes that are time- or activity-based.

Once a problem is identified, shorter captures can be used to troubleshoot. By initially looking at the longer pcap, you should be able to identify the cause or the frequency of the problem, or the time of day during which it occurs. Use this information to capture a pcap that is five to 20 minutes long, to see if your work fixed the problem and increased the network health. In some cases, it may be good to force a command or action during the capture period to ensure the fix is applied correctly (e.g. confirm reply on read-property is no longer an error).

Intended use of Visual BACnet	Recommended capture length
General system health check	1 hour
Troubleshooting and validating fix	5-20 minutes

 
If you are using Visual BACnet for a particular problem, ensure that the action or commands triggering the problem occur during the capture period. Note that some BAS and controllers include a packet capture feature, which are easy to use and require no additional software or hardware. Please ensure the capture file has an extension of .cap, .pcap, or .pcapng. If it does not by default, append a .cap before uploading to Visual BACnet. We recommend performing regular checks on your network’s health — monthly, weekly, or daily if possible — to ensure the system is running smoothly.