[v6test] IPv6 prefix used for experiment - 2001:4978:8::/48

[Kevin Day]

Since some operators have expressed concern about our experiment  
breaking their network, I've been asked to pre-announce what address  
space will be used for this experiment.

2001:4978:8::/48 will be used exclusively for this experiment.

While I'd really really like to try to work with anyone on their  
concerns, if you absolutely must rate-limit or blackhole this  
experiment, please block ONLY that /48. There are completely unrelated  
services announced from our ASN and from our /32 that we'd really not  
like to have negatively affected by this experiment.

In short:

If you're worried about us breaking something of yours by having a lot  
of v6 traffic on your network, contact me off list or post here on the  
list with your concerns. If you have to block something, block only  
that /48.

Thanks!

-- Kevin