How Does DNS query ns servers.
Okay, this is going to tax some of your brains, but here we go.
Lets say I have 4 ns records for a said subdomain(s). When a dns server queries to get these record(s) it is sent a list of ns records from my upper level ns server, cloudflare. It then queries said ns record(s) and gets an answer for A or AAAA.
My question is do modern dns servers query NS via a round robin, or do they query all to decrease look up times / test to see which is the best / closest host?
I.e. the dns server already has the ns records, and it now needs to look up the exact subdomain A or AAAA record. How does it make its choice on what to query for said subdomain record.