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by cryptonector 1024 days ago
Nothing about PMTUD?
2 comments

FWIW, I put together a PMTUD test site you might find interesting http://pmtud.enslaves.us/
Nice URL!
For TCP sockets I'd rather just MSS clamp on the internet gateway. On top of too many things just dropping PMTUD, enabling it results in a slower process while MSS clamping hijacks the initial TCP open messages directly.
There's PMTUD that doesn't depend on ICMP.
For TCP in Linux the only thing I know of is net.ipv4.tcp_mtu_probing=2 which is still slower than clamping at the edge. You can also run into weird slowdowns in cases with packet loss even after the initial discovery. If you don't have a way to clamp but absolutely need the interface to have jumbo enabled for local traffic performance it's probably the best fallback but even then I'm not sure it's worth the extra headache it causes.