"Root server instance: A portion of a root server's infrastructure that serves root data from a particular site, which may consist of single or multiple physical devices.

Anycast instance: another name for a root server instance."

there have always been more than one routing instance of a server identity in some site.

IMHO, I didn't say otherwise in my text. An instance is welcome to have more than one route per site. Or maybe you're arguing that two "instances" can occur at a site. Note that my text also didn't say "unique at a site" either.

(but my text was a starting proposal to think about, not such much final wording choices)

Wes Hardaker

USC/ISI