Video RTP stream over VPN client, dropped frames/fragmentation

Unanswered Question
Oct 29th, 2009

Hello NetPros!

We have a streaming video server (Genetec Omnicast) and it works fine over the LAN. However, when connecting over VPN to view video remotely, the video is practically unusable.

If running Wireshark to capture the stream, it shows over 50% packet drops with "wrong sequence number" errors or "incorrect time stamp" errors.

If we ping the remote router's inside interface with packets above 1276 bytes it wants to fragment. So I'm assuming the video server is sending 1500 byte packets and for whatever reason these cannot easily be reassembled after fragmentation.

Is there a setting we can set on the router that would alleviate this problem? 1276 bytes seem quite small for MTU but we haven't set it anywhere manually. If we don't clear the DF bit, then we just see a lot of dropped packets.

Any help would be greatly appreciated!

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Joseph W. Doherty Thu, 10/29/2009 - 18:17

Assuming your router supports PMTU but your video server doesn't, you might try reducing the MTU on the video server's NIC to avoid fragmentation.


Yes, also agree 1276 seems rather small for a VPN MTU. Would expect 1400 something.


This Discussion