Who does source address validation? (was Re: what's that smell?)

Just out of interest how do you co-ordinate use of RFC 1918 addresses
and routes amongst your customers? Do you run a registry for them, or
do you just let them fight it out and the one with the biggest packets
wins or something like that?

there's a registry. we also maintain IN-ADDR zones for them and
encourage the use of "stub" zones in customer name servers in order
to direct their queries toward the local RFC1918 registry.

now, i'll admit that it took almost two hours to get this working
initially, and almost a week for it to settle down, and that the
network is small -- only about 50 "customers". but for the last
few years no RFC1918-sourced traffic, nor any RFC1918-IN-ADDR DNS
query, has egressed from this network. it can't be THAT hard.