The specific query that led me to try and unpick this process was:
Will a DNS lookup for a subdomain, such as
assets.example.com, be faster if the parent domain,
example.com, has already been resolved?
By my (naive) understanding, the basic process for translating a domain name into an IP address is quite simple. The addresses of the thirteen root servers, who know how to resolve top-level domains like
net, are effectively hard coded in network hardware. In the case of a lookup for
example.com, our local DNS server, probably our router, queries one of these root servers for the domain in question, and is referred to the top-level nameserver for
com. It then asks this nameserver if it knows how to resolve
example. If it does, we're done, if not, we're referred on to another server. Some of the servers in this process may be caching, so that for a time our local router will now know offhand where to look for
Still, I don't really get it.
- I know there are other intermediate DNS servers, such as those provided by ISPs. At what point are they queried?
- If the
comTLD nameserver we're referred to does not know how to resolve
example, is it right to say that's the end of the line:
example.comcannot be resolved?
- When I register a domain and configure nameservers, am I in effect editing a group of NS records for my subdomain in the database used by the nameservers for that TLD? Does the registrar itself maintain "proxy" nameservers?
Wikipedia explains that some DNS servers combine caching with a recursive query implementation which allows them to serve cache hits and reliably resolve cache misses. I don't understand how these servers come to be queried, or how (even broadly) the resolving algorithm works. Are all authoritative
com nameservers, for example, exact mirrors, or would a resolver have to try each in turn?
Looking back at my initial question, I might take a very speculative stab at "no", assuming the A records are both on the same nameserver. I would be very grateful to anyone who could reduce my ignorance!