google path mtu?

Tore Anderson tore at
Fri Jan 23 07:32:47 CET 2015

* Mikael Abrahamsson <swmike at>

> So I guess the problem this time was some Google servers sending me 
> PTB=1280 and then Chrome not taking this into account when sending
> UDP packets when using QUIC, resulting in fragmented IPv6 packets
> (which works very badly in real life), and then not handling this
> situation by doing fall-back to something else.

I highly doubt that Google would be sending you PTBs. 10 SEK says it's
your tunnel ingress router (i.e., your Airport Express)...

But this could be found out, run "tcpdump -nvi eth0 'icmp6 and ip6[40]
== 2'" in a terminal while reproducing the problem and see what's the
source address of the PTBs?


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