question about mirroring

Dear all

We have a question and would be appreciated to hear from you.

We saw that RIPE is currently mirroring RADB
RIPE:2:N:2278327-8326558
RADB:1:N:397470-400159
APNIC:2:N:2-2157249
ARIN:1:N:2-3830651
VERIO:1:N:20896-67078
JPIRR:1:N:755-28963
AFRINIC:2:N:2-157989

we would like to know in this case, what the mirror mechanism is used
and how it is configured ?
As we know RADB runs Irrd while RIPE runs whoisd.

Thank you very much.

Nguyen,
NTT Communications