NS list does not match list from parent zone

I'm attempting to figure out an error message that I got from dnsstuff.com when examining my DNS records. The error reads as follows.

NS list does not match list from parent zone. This should be addressed because queries for this domain may require an extra lookup (and more overhead) because there is no direct relationship between the NS records at the parent and the NS records at the authoritative servers. This can cause delays. The mismatched NS list is:

nameserver ns1.domain.co. | xxx.xx.xxx.xxx is missing NS2.domain.co. | yy.yyy.yy.yyy

There are a couple questions I have regarding this.

1. What is the difference between a parent and authoritative zone? In other forum posts I've seen, the seem to be used interchangeably (although that could be my misperception).
2. What does it mean for the NS list not to match the list from the parent zone? What is "the list from the parent zone" to which they refer?
3. How might you recommend that I resolve this?

In case this affects any answers, I'm running Virtualmin on Ubuntu 12.04.

Any help is appreciated. Many thanks in advance!

Solution 1:

1. For eg example.com the authoritative zone is example.com and the parent zone is com. You manage the delegation information (NS and A/AAAA glue records) in the com zone through your registrar.

2. The delegation information in the parent zone (NS and A/AAAA glue records) should match your NS and A/AAAA records in the authoritative zone.

3. Ensure that the records match. You should know which NS records are desired, ensure that both the delegation information and your authoritative records match the nameservers that you intend to use.