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The twamp-test sender timestamp is not well decoded

asked 2024-10-03 22:27:33 +0000

jpmfa gravatar image

updated 2024-10-03 22:31:23 +0000

Hello,

I've noticed today this bug in WS in twamp udp test packets: TS from Sender:

Timestamp: Oct 3, 2024 23:08:20.750977838 GMT

0xeaa99454c040156a

Here we are fine.

In the twamp reflector message we must copy this TS in the sender TS, so I copy exactly the same bits but the decoded result in Packet Details is:

Sender Timestamp: Oct 3, 2094 23:08:20.-1069542038 GMT

which is wrong for the same 0xeaa99454c040156a

I was struggling to see where is the issue with my reflector packet but finally it is wireshark issue.

Can you fix this one? Basically you need to decode the sender TS like the first TS in the packet and all will be fine.

I'm using WS 4.4.0

BR,

João

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With sample capture attached to 16264: TWAMP dissector not working do you see the same issue?

Chuckc gravatar imageChuckc ( 2024-10-04 00:51:14 +0000 )edit

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answered 2024-10-04 00:41:19 +0000

johnthacker gravatar image

updated 2024-10-04 00:59:11 +0000

File an issue here and attach your capture file, and someone may be able to fix it.

Before you do, can you check the value of the z bit in the two packets? I would assume that they are not the same. That controls whether the NTP time format or a time format related to the Unix epoch is used, and the difference in epochs explains the difference. Did you copy the error estimate field?

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0 for the Z bit indicates NTP time format, and 1 indicates the PTP time format. The same 8 byte value you gave has two different values if interpreted as a NTP time format vs a PTP time format.

johnthacker gravatar imagejohnthacker ( 2024-10-04 01:00:53 +0000 )edit

Ok, looks like Wireshark has reversed handling for the Z bit in that case. https://gitlab.com/wireshark/wireshar...

johnthacker gravatar imagejohnthacker ( 2024-10-04 01:21:14 +0000 )edit

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Asked: 2024-10-03 22:27:33 +0000

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Last updated: Oct 04