There is no
dir.upspin.io, as far as I know. Are you referring to
upspin.io/doc/arch.md? There the machine name is like
upspin.example.com or
camera.example.net, also mentioned in the doc but not existing in reality.
As best I recall, all the references to
dir.upspin.io in
key.upspin.io/log were placeholders while setting up new accounts, replaced by actual dirservers once the account was fully operational.
Or perhaps my memory is fading that there really is supposed to be such a machine? Happy to be enlightened.