Say I've operating ns1.example.org and ns2.example.org on which I want to host the zone file for example.com
When I go to my registrar and purchase example.com , I will tell my registrar that my nameservers are ns1.example.org and ns2.example.org
My question then is, why do I then also need to specify those nameservers in the zone file for example.com ? Haven't I already told the .com nameservers where to lookup information on example.com , making the NS records redundant?
Clearly I'm missing some crucial fact...
NS Records inside the zone are authoritative, the ones received from the registrar (the ones delegating the domain) are not, so if a server receives any difference from those records, the authoritatives win. Also, servers listed in the NS record will receive a NOTIFY in case of zone changes (so the slaves can check for updates and so on). One last thing, the RFCs 1034 and 1035 say that they must exist, so they must exist!