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RTP Packet Lost

asked 2019-04-15 11:23:35 +0000

anas.awad gravatar image

I cant understand the issue here, we first found the cause of this issue that the firewall was inspecting RSTP traffic and some how sometimes blocking it. but after remove the inspection policies from the firewall it worked fine.

Now the same issue happen again (some how still considered differently) and some cameras out of 4000 cameras, showing delay in the stream, or break in the record. the capture showing me this "previous segment not captured (common at capture start)" this is has many reasons: it might be wireshark could not capture or wire issue. how to figure out the cause. Thanks

Please excuse my language.

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answered 2019-04-16 17:53:24 +0000

Hi Anas,

I've answered a similar question about previous segment not being captured.

TCP segment not capture may be normal if they are seen at the beginning of a capture or at least if you started capturing packets after the TCP conversation had begun. It can also mean there are dropped packets either on the network or on the capture device. Check Statistics -> Capture File Properties (CTRL+ALT+SHIFT+C) to see if there were drops. (The capture device may not support populating that field.)

To me it looks like you are seeing the effect of packet loss.

Is the signalling or the camera feeds that are lost?

You mention RTSP and cameras so do you mean Real Time Streaming Protocol because to me RSTP is Rapid Spanning Tree Protocol?

RTSP over TCP would make sense for seeing segments not capture.

Your subject line, however, reads RTP so is it Real-time Transport Protocol but over TCP? I'm used to seeing it over UDP myself.

If you capture on the firewall, try to capture on the ingress and egress interfaces to verify the firewall is not dropping the packets.

Look at interfaces counters on the path the traffic takes.

Hope this helps.



(If this answer helps, vote on it to help others.)

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Asked: 2019-04-15 11:23:35 +0000

Seen: 1,629 times

Last updated: Apr 16 '19