[nitinag]

Registrars provide the nameservers you give them to the TLD itself. So, resolution doesn't depend on the registrar's infrastructure unless you're using the registrar's nameservers directly.

It works like this: Root -> TLD -> NS -> NS -> ETC.

Root Servers are fixed and everything drills down from there: https://www.iana.org/domains/root/servers

A visual example of how the nameserver hops work starting from the root using the nameserver delegation view feature of our dns lookup tool: https://www.misk.com/tools/#dns/[e-mail]-...

(Disclosure: I work @ Misk.com, an ICANN accredited registrar, our link above)

[buzzdenver]

Thank you for the reply. Can you explain how "provide" works in your first sentence? How does the .com TLD server know who registered google.com ? Seems like TLD servers still have to know the list of possible registrars where one can register a domain for their TLD.

[LIV2]

Yes, registrars have an agreement with the TLDs and have API access that allows them to submit requests for DNS delegation, transfers, registrations, creating glue records etc.

The registrar will send a request to the TLD to essentially ask that they delegate your domain to a specified nameserver which will add records to the TLDs zone for your domain