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yesterday I recognized that git cloneing repositories from my private GitLab instance wasn't working consistently. My internet connection is fine and I can also visit GitLab's web interface without any problems. I then checked the network packets via Wireshark and encountered some strange behaviour:

  • Approx. 70% of all HTTPS requests are just passing fine
  • The other 30% get timeouts and I see [TCP Retransmission] [TCP Port numbers reused] notifications when the timeout occurs
  • I used another server outside of my home network to check whether the problems occurs from other networks as well. It works fine all the time
  • I also get the same problems when I check the HTTPS connection via termux on my mobile device which is not connected to my home network but to the same provider via 4G
  • When I use the browser instead of curl, git or python I get no timeouts at all
  • ICMP packets are passing fine
  • When a timeout occurs, my server's firewall doesn't receive any packets. That is another hint on my server being fine

I first thought of faulty network hardware but I am sure that's not the problem due to the problem occuring on my mobile device via 4G as well.

The only thing I can imagine is that some device of my provider is faulty. My connection uses a dualstack-lite tunnel.

I'd be happy if someone has ideas...

Kind regards from Germany

Images:

Wireshark output

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  • so it's happening on both your ISP network and your cellular (4G) network? that does eliminate just about everything you could control, unless you are mistaken and the phone is using wifi. do you have the same provider for both network connections? Commented Feb 9, 2023 at 22:50
  • Hi Frank, thank you! I actually tried it while pausing at the gym and I'm not logged into their network, i.e. that shouldn't be the issue. I got the same provider (Vodafone Germany) for both my mobile and my cable. Furthermore I'm kinda concerned that the problem could also be caused by my dedicated server setup but I see no obvious issues and the packets come in. Really confusing.
    – Thomas B.
    Commented Feb 9, 2023 at 23:02

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