google path mtu?

Lorenzo Colitti lorenzo at
Fri Jan 23 03:55:57 CET 2015

Thanks for reporting this. What was the effect? Connections just getting
stuck? Was there fallback to IPv4?

Personally I don't understand why everyone behind a manually-configured
tunnel doesn't set the MTU in the RA to the MTU of the tunnel... but that's
not an excuse for things not working.

On Fri, Jan 23, 2015 at 11:45 AM, Mikael Abrahamsson <swmike at>

> I had another problem with Youtube just now, with Chrome+OSX. I saw my
> machine sending fragmented UDP-packets to google on 443, which it was not
> getting any responses to. On a hunch, I disabled QUIC in Chrome which made
> things start working again.
> 03:20:45.891286 IP6 2001:470:X > 2a02:808:1:100::c: frag (0|1232) 59430 >
> 443: UDP, length 1350
> 03:20:45.891286 IP6 2001:470:X > 2a02:808:1:100::c: frag (1232|126)
> --
> Mikael Abrahamsson    email: swmike at
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