AVTP Wireshark Analysis

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JohnnyRoehn
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AVTP Wireshark Analysis

Postby JohnnyRoehn » Tue Oct 11, 2016 1:31 pm

Hello,
I've tried to watch the AVB traffic via port mirroring on my switch and I could see all the AVTP packets sent by the AVB talker. The packets look fine but I am wondering about the amount of packets. The talker stream consists of 8 channels thus one AVTP packet consists of 6 samples per channel which makes 48 samples in total. Finally there should be 8000 packets per second at 48000 kHz BUT I can only see about 16 AVTP packets per second in Wireshark. Additionally all the sequence numbers of the packets all look fine and there are no gaps so Wireshark shouldn't leave any packets out. This doesn't make sense to me, can anyone help me?
peter
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Postby peter » Wed Oct 12, 2016 10:23 am

Hi JohnnyRoehn,

Yes, you should be seeing 8000 AVTP packets per second. Can you give a bit more detail of the configuration you are using and where you are monitoring the traffic in order to try to observe the packets?

The other basic questions to ask are:
- What are the endpoints?
- Is the audio playing? In which case the packets must be flowing but just not being logged where you are trying to observe them.

Regards,

Peter
JohnnyRoehn
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Postby JohnnyRoehn » Wed Oct 12, 2016 12:08 pm

The setup consists of a XMOS LC AVB talker which is connected to an Extreme X440 Switch and 4 XMOS DC listeneder Boards which are connected to the switch via daisy chaining. Additionally my laptop is connected to the mirroring port of the switch, which mirros all the traffic to and from the XMOS LC talker Board. This traffic is sniffed by Wireshark. Audio is playing out on all of the XMOS DC listener boards so I should normally see all the AVTP packets in Wireshark.

Best regards,
JohnnyRoehn
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ers35
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Postby ers35 » Wed Oct 12, 2016 12:08 pm

Is your laptop a Mac? Try using Windows or Linux. See my other post: https://www.xcore.com/forum/viewtopic.p ... 460#p23460

What commands did you use to enable mirroring? Paste the output of "show mirror".

Try these commands. For example, to mirror port 1 to port 8:

Code: Select all

configure mirror add port 1
enable mirror to port 8
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larry
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Postby larry » Wed Oct 12, 2016 3:45 pm

I would also check the endpoint's source MAC address (to be sure it is the correct stream) in the packet trace as well as AVBTP sequence number (sounds like you've checked that already).

I am not sure how port mirroring works with 1722 on the X440. I wonder if mirroring doesn't set up hardware tables properly for the multicast MAC address that the 1722 stream has reserved and the packets end up in software where some get dropped.

Is it 16 packets per second consistently or varying?

Do you happen to have a throwing-star wire tap to use instead of port mirroring?

https://greatscottgadgets.com/throwingstar
JohnnyRoehn
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Postby JohnnyRoehn » Wed Oct 12, 2016 4:29 pm

I am using a Windows laptop and I have the same result on a Linux Virtual Machine. I did exactly the same mirror setup on the x440.
The source address and the sequence numbers seem to be correct altough sometimes there are jumps in sequence numbering. I guess the reason is the USB ethernet adapter, which is not able to capture more packets per second. The maximum of AVTP packets per second ist about 32. I captured 16 per stream when there were 2 talker streams active.
I don't have a throwing star wire tap. The next attempt would be using a MAC with a Thunderbolt adapter, but this doesn't work?
JohnnyRoehn
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Postby JohnnyRoehn » Wed Oct 12, 2016 5:45 pm

okay, I solved the problem by using another x440 switch! Now I can see all the AVTP packets passing the network:) Thanks for your support!

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