IPv4 vs. IPv6 Ethernet Performance

[jb]

Norbert Aschendorff <norbert.aschendorff <at> yahoo.de> writes:

> ... 
> Little table (values in Mbit/s):
> 
> Configuration		v6	v4
> =======================================
> Linux -> Linux		925	935  # <= This could be v6's 40B header
> 				     # vs. v4's 20B
> Linux -> FreeBSD	450	700
> FreeBSD -> Linux	455	920
> =======================================
> 
> The FreeBSD->Linux value shows that the ethernet chip on the FreeBSD
> machine (it's Intel stuff on both sides, using the em(4) driver on
> FreeBSD) is able to send at full 1G speed. But why is IPv6 so slow?
 
Norbert,
may I ask you to provide one more stats item for this table, if you can ?
  FreeBSD -> FreeBSD 	???	???

Thanks,
jb