on 17-07-2021 16:01
I have noticed some packet loss recently on my broadband connection.
After doing some investigatory ping tests I noticed that packets above 1472 bytes were being dropped within the Virgin media network. Pings above this size worked fine to the next hop address after my VM Hub, and below this size work all the way through. Anything above this size is dropped at brnt-core-2b-xe-202-0.network.virginmedia.net [62.252.212.37]
This suggests that the DF flag (don't fragment) is set somewhere in the network and would be dropping large packets (above 1500 bytes) instead of fragmenting and forwarding them on. There is a possibility that a firewall rule is blocking large ICMP packets but usually these rules are set to block all ICMP.
I'm sure this was not the case before, and I have noticed recently dropouts in team video conf calls.
I did log an email explaining this but got the usual standard bull$*** response.
Can someone at VM 2nd line support look into this? Is anyone else noticing packet loss (poor quality video calls)?
Answered! Go to Answer
on 17-07-2021 16:33
on 17-07-2021 16:27
on 17-07-2021 16:32
Who are you trying to ping? 1.1.1.1 supports above this size, but 8.8.8.8 will not even accept 80.
on 17-07-2021 16:33
on 17-07-2021 16:47
I had jumboframes enabled on my network, but even after turning off the same result. So your answer makes sense, thanks.
Just a bit strange that ICMP fragments are responded to by the next hop, but nothing further.
Yes possibly fragmented UDP packets are being dropped in the network. I've also noticed packet loss recently in some online games (only for downlink).
Not sure how to prove this though.
on 17-07-2021 16:54
on 17-07-2021 16:56
Thanks all for the responses. I'm now guessing that there is just congestion somewhere in the network causing the problem as pings above 1472 bytes are working to some internet destinations.
It would be more noticeable for real time traffic like gaming and video calls which would explain what I've been experiencing.
17-07-2021 17:27 - edited 17-07-2021 17:28
You can use this UDP tool to test fragments by a 4G connection and Wireshark to a destination port say 49141 to VM
http://startrinity.com/VoIP/NetworkTester/NetworkTester.aspx
Then to test back on your VM connection send a connect back on the same SNAT source port used for 4G as destination from and source port 49141 (49140 as it ups the port you set by 1)
on 18-07-2021 00:54
I’ve my MTU set to 1472 on my Router and don’t seem to have any problems? Am I missing something here?
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on 18-07-2021 07:23