LabVIEW Time Sensitive Networking (TSN)

Reply
This is an open group. Sign in and click the "Join Group" button to become a group member and start posting.
Highlighted

Using a Computer with Wireshark to Troubleshoot a TSN Device

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.

Wireshark Capture.png

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.

TSN Data.png

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.

0 Kudos
Message 1 of 3
(1,350 Views)
2 REPLIES

Re: Using a Computer with Wireshark to Troubleshoot a TSN Device

Hi Burt

 

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 ? 

0 Kudos
Message 2 of 3
(328 Views)

Re: Using a Computer with Wireshark to Troubleshoot a TSN Device

Hi Muhammad,

 

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:

 

  • As Burt mentioned, any kind of network TAP will introduce latency.
  • For synchronization applications, the latency is usually accounted for by the 802.1AS protocol and shouldn't affect synchronization. If the latency in the connection rises above 800 ns, you may see loss of synchronization due to the 802.1AS spec. On TSN-enabled cRIO's, you can increase this threshold if you need to. It's accessible via property node and is called Neighbor Propagation Delay Threshold. The property is not supported on TSN-enabled cDAQ's.
  • Similarly, for deterministic streaming applications you will need to account for the delay introduced by the TAP. You will need to increase the timing window in which data is valid, otherwise you will lose data.
Austin
Product Support Engineer
National Instruments
0 Kudos
Message 3 of 3
(314 Views)
Reply
This is an open group. Sign in and click the "Join Group" button to become a group member and start posting.