Google's stats claim that it's 10-20ms for many countries, for example both the US and Canada show the latency impact of v6 as being -10ms. This is per round trip too -- between the connection handshake, congestion window slow-start and serialized requests it adds up to something significantly bigger than a few hundred microseconds.

> let's not forget IPv6 is two separate island because two tier-1 carriers refuse to peer (Cogent & HE).

The Cogent island must be very small, because I'm single-homed on HE and had actually forgotten about that.

Or perhaps v6 isn't split into two separate islands after all, and this is just yet another weird claim people make about v6 that doesn't match reality.

Latency wise, I am not noticing any difference (at least in ICMP).

ycombinator@Mainframe:~$ ping 8.8.8.8

PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.

64 bytes from 8.8.8.8: icmp_seq=1 ttl=119 time=24.3 ms

64 bytes from 8.8.8.8: icmp_seq=2 ttl=119 time=24.1 ms

64 bytes from 8.8.8.8: icmp_seq=3 ttl=119 time=23.9 ms

64 bytes from 8.8.8.8: icmp_seq=4 ttl=119 time=23.9 ms

^C --------------- 8.8.8.8 ping statistics --------------------

4 packets transmitted, 4 received, 0% packet loss, time 3004ms

rtt min/avg/max/mdev = 23.901/24.053/24.291/0.157 ms

ycombinator@Mainframe:~$ ping6 2001:4860:4860::8844

PING 2001:4860:4860::8844 (2001:4860:4860::8844) 56 data bytes 64 bytes from 2001:4860:4860::8844: icmp_seq=1 ttl=118 time=23.5 ms

64 bytes from 2001:4860:4860::8844: icmp_seq=2 ttl=118 time=24.0 ms

64 bytes from 2001:4860:4860::8844: icmp_seq=3 ttl=118 time=23.9 ms

64 bytes from 2001:4860:4860::8844: icmp_seq=4 ttl=118 time=24.0 ms

^C ------- 2001:4860:4860::8844 ping statistics -------------------

4 packets transmitted, 4 received, 0% packet loss, time 3005ms rtt min/avg/max/mdev = 23.517/23.845/24.008/0.200 ms