4 ms·

Thanks for the response. Interesting, do you mean Android has PMTU detection disabled in that Google is filtering "fragmentation needed but DF bit set" ICMP rep

Thanks for the response. Interesting, do you mean Android has PMTU detection disabled in that Google is filtering "fragmentation needed but DF bit set" ICMP replies? That would be very surprising for Google I would think. Or are you referring to something else?

toast0 8y ago
Android either doesn't enable PMTU detection, or it's only enabled in recent versions, or it's configured such that it's not effective. I've seen pcaps with iOS devices doing it though. I don't think Google would intentionally filter out the ICMP fragmentation needed packets, but there are lots of problems actually getting them, between routers that drop packets without sending them, firewalls that drop all ICMP, and NAT devices that don't know how to direct them to the underlying client. Edit: sorry I really mean PMTU probing. If you got a connection, but no acks when you send a large packet, after a significant timeout, it's worth trying to send smaller packets, even if you didn't get an icmp that says you should.
- bogomipz 8y ago
  Ah OK, interesting that this behavior exists in iOS as well. Thanks for the clarification. Cheers.