Throughput calculation with Wireshark

[WaKo]

Hi,

I want to calculate throughput rate using data that nRF52840 dongle working as sniffer captured.

Wireshark shows 'time' , 'delta time' and 'packet time'.

I think 'time' is incorrect.

For example, about IFS,  'delta time' shows 150 us but 'time' shows more than 1 ms.

・What dose 'time' means ?

・Do ’delta time’ and 'packet time' show correct time ?

Best regards

[Simonr]

Hi

Your assumption that time is incorrect in regards of data transmission is correct. This parameter is at what time each packet is received over the COM port to Wireshark, and has nothing to do with the on-air transmission per se.

Delta time should indeed show the correct time that each radio event takes to complete, so that should show you the correct time between each advertising packet. As for the "Packet time" you are seeing, I don't have this parameter on my Wireshark, can you show me what "Field" this is in the Wireshark "Column preferences"? You can get to the menu pictured below by right-clicking any of the columns in Wireshark and press "Column preferences" in the dropdown menu.

Best regards,

Simon

[WaKo]

Thank you for your reply.

> This parameter is at what time each packet is received over the COM port to Wireshark

If nRF52840 dongle working as sniffer receives large data many times in a row how dose it works ? 

May sniffer fails to receive some data because on-air transmission is faster than transmission over COM port ?

"Packet time" is here(see attached picture)

 

[Simonr]

Hi

As I think you might see, Wireshark receives the data ~5 packets at a time in your case. On the 2MBPS PHY with DLE and L2CAP, it is confirmed that the nRF Sniffer will not be able to send all the data from the chip over to Wireshark in time, indeed. In more high-end Sniffer solutions, like Ellisys and Frontline should be able to capture all packets at this data rate.

The Packet Time you are referring to shows the time that the packet itself uses on air.

Best regards,

Simon

[WaKo]

Thank you for your answer.

> On the 2MBPS PHY with DLE and L2CAP, it is confirmed that the nRF Sniffer will not be able to send all the data from the chip over to Wireshark in time, indeed.

Dose this means that nRF Sniffer sometimes can't send data to Wireshark in time but all the data are captured and sent to Wireshark ?

If I calculate throughput rate from Wireshark, using "delta time" and "packet time" is the most accurate way ?

Best regards

[Simonr]

Hi

At this maximum throughput in the 2MBPS PHY and with DLE + L2CAP, the nRF Sniffer will fill its buffer rather quick, and while it sends data from the chip to Wireshark, the device will miss a few packets before getting back to listening.

Yes, you can estimate a throughput rate from Wireshark using the delta time and packet time parameters.

Best regards,

Simon