Most TSN traffic is not connection-based; devices are configured to send specific data at specific intervals and generally don't care what device is on the other end. Because of this, it is possible to connect a computer running Wireshark directly to an end node or to a port on a switch to gather valuable troubleshooting information. Wireshark can display TSN data packets as well as PTP and LLDP traffic. Gathering this information is usually as simple as installing the latest version of Wireshark and starting a capture on the appropriate interface (once the appropriate network connections have been made). Below is an example Wireshark capture from a computer connected directly to a cRIO-9035 Sync.
When examining the content of a TSN packet, it may be possible to see the multicast DMAC as well as the data in the payload. The specifics of the LLDP announcement can also be examined.
While very powerful, there are many caveats to using Wireshark for troubleshooting. First, different computers may return very different information within a capture. The information that gets returned can vary based on NIC's, OS's, and other factors. For example, some setups may filter out LLDP or PTP traffic entirely. Some setups may filter various information within the frame as well. For example the capture above does not show the VLAN ID. Another setup may filter out different information like the DMAC. Because of this, it is best to first check the capabilities of a particular Wireshark setup on a working system before using it to troubleshoot something that is broken.
In addition to information inconsistencies, this approach also does not return accurate timestamps and may change system behavior because of the network break that it causes. These limitations can be avoided using time-aware network taps that can be inserted in-line with a communication pathway. These taps introduce a small amount of communication latency, but will otherwise allow the network to function as normal. The downside of this approach is simply the additional hardware required.
Despite limitations, a computer running Wireshark can be an extremely valuable TSN network troubleshooting tool when used appropriately.
What would you say about using Wireshark with one of the TAP ( Test Access Point ) devices. For example the TAP from Profi Shark. Could you comment on using ProfiShark with WireShark for TSN Monitoring and Troubleshooting ?
A ProfiShark TAP device is a good tool for troubleshooting. There are a few things to be aware of when using one of these devices: