Posts by henkpls

    I understand that you are curious , so here's the reply:

    1. "we are currently investigating this problem and we involved our NOC. Thank you very much for the nice script you have written for testing purposes.
    2. We can definitely reproduce the issue."

    Do you have any experience how long it will take for the NOC to fix this? Just Curious :)

    RTP packets are not a problem. For SIP, packets have increased over the years as functionality was extended. It's a known problem that SIP packets over UDP are fragmented. But over a total of 5 servers I have, I can send large UDP packets from one to the other including the route over internet. Only on the NETCUP network these are dropped due to unknown reasons to me.

    My eth0 device has an MTU of 1500, so there is in my opinion no need for MTU discovery (and I also tested in recovery mode without firewall). Also, the large test packet is fragmented at the source, as otherwise I think (I'm not an expert on this) it cannot travel the internet and arrive on servers from other providers.

    I did some more testing and found that this could be caused by a network firewall, in the captured packets I see Netcup is using a Juniper device. This lead me to this post which might explain the dropped packets:…x?page=content&id=KB31437

    Yes, but I was on a dead end. This is the last answer I got:

    1. i've discussed the issue with one of our network engineers and he is also convinced, that this is in fact an issue with mtu and therefore no issue in our infrastructure.

    So I expect to get this reopened now. Thanks for the help!

    Hi all,

    I have a RS2000 G8 server with 4 CPU and I'm having problems with large (>1472) SIP (UDP) packets which have a loss of almost 100%. Of course changing to TCP fixes the problem, but not all users can switch so easy. I have servers with 2 other providers where there is 0% packet loss. Support was helpful and changed me to another rack, but still the same problem.

    To test, I'm using socat on an open port like this:

    socat -v UDP-LISTEN:35000,fork PIPE

    and send packets from a remote server with ( This works 100% to one of my other servers, so I think the test is correct.

    Today I did a final test and tested in recovery mode with the same results. So now I'm out of idea's and hope that someone can help me.