TEARDOWN and

Answered

Yoshi Sei

August 26, 2020 07:11

Hi , Nx Team !

I've set up NxWitness Server(4.1.31398) on Jetson Nano with 2 IP cameras.

It's system has been run currently , however it have occurred "Network issue" occasionally. (about every 3 hours)

When I invested "Network issue" , I found the following things in the packet log of ethernet .

    Request: TEARDOWN rtsp://172.16.0.204/ONVIF/MediaInput?profile=def_profile2 RTSP/1.0\r\n

 

I personally guess that it s possible that TEARDOWN make occur "Network issue".

Could you please tell me about the cause of "Network issue" ?

if you need more information about the issue, I will send you it.

 

Best Regards,

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• Official comment

  

  Norman

  • Network Optix team

  August 26, 2020 08:12

  Hi Yoshi Sei,

  I assume that before the TEARDOWN there are lost RTP packages. 
  Most likely the cameras are overloaded and can't keep up with the requests from the server. 

  Often you can avoid this be reducing the load on the camera by reducing the framerate and/or the bandwidth or both. 
• 

  Yoshi Sei

  August 26, 2020 09:10

  Hi Norman,

  Thank you for your suggestion, I realize I should remove more Influencing factors (other devices) from this test environment,

  because I found "RTSP [TCP Spurious Retransmission]" from these logs .(about every few minutes)

  I try to adjust this environment .

   

  By the way ,please teach me the condition  of occurring "TEARDOWN" in details.

  (If  the lost of RTP packets occurs even once, NxServer sends TEARDOWN to an IP camera? )

   

  Best regards,

  0
• 

  Norman

  • Network Optix team

  August 26, 2020 11:20

  Hi Yoshi Sei.

  TCP Spurious Retransmissions should be avoided as much as possible and often this can be done by reducing the load on the camera by reducing the framerate and or the bandwidth. 

  > By the way ,please teach me the condition  of occurring "TEARDOWN" in details.

  That question is a lot shorter than the answer.
  
  The summary is that there should be a TCP handshake between the Nx server and the camera, in case there TCP handshake can't be finished, you'll get a retransmission, in your case a spurious retransmission, in laymen terms, it try to do the handshake once more. If it continues to fail, eventually there will be a TEARDOWN to end the retransmissions. 

  On THIS website, you can find everything in detail about TCP/IP. This website is also available as a book, which is actually an awesome reference. 

  To learn more about Wireshark and the TCP/IP protocol, the following books are also highly recommended: 

  • Learn Wireshark
  • Wireshark 101
  • Practial Package Analysis

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• 

  Yoshi Sei

  August 27, 2020 00:24

  Hi Norman,

  Thank you for your answer in detail and recommendation. I understand the general concept of TCP handshake .

  My intention is to grasp the specification of  Nx Server layer protocol (application layer).

  If only the TCP layer is the cause concerned with this phenomenon, I shouldn't ask you.

   

  At first,  I should remove more Influencing factors (other devices) from this test environment.

  I will contact you if there is anything else.

   

  Best regard,

   

   

   

   

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• 

  Norman

  • Network Optix team

  August 28, 2020 08:05

  Hi Yoshi Sei,

  Just let us know if we can do something in this case for you. 

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