3 ms·

Fun fact, was observing periodic latency peaks on some customer network. TCP analysis would show a resend after an icmp 'too big' packet from a middlebox. Fine.

Fun fact, was observing periodic latency peaks on some customer network. TCP analysis would show a resend after an icmp 'too big' packet from a middlebox. Fine. Once at connection establishment or rather at the first PSH over the default MTU, right? But why periodically? Well Linux re-raises the path mtu periodically, iirc in case of icmp spoofing... Is it different here for mss-based discovery? You say permanently?

jsnell 5y ago
That was my recollection, but looking at the source I don't think that was correct.
- touisteur 5y ago
  Ah thanks. Will have to open tcp.c, but it gets crazier every year it might take some time... It would make sense to keep it permanently if the justification is purely based on the risk of icmp spoofing. But TCP connections can be very long-lived and the network might change under your feet, even worst if you're doing some bonding/teaming or container-/connection-migration, it might be a good idea to probe the path mtu again. It's just a pain from a latency perspective. I wish I could skip a bit of a stream without re-establishing the full connection.