uncertain about 'expired domain names' ...

I think all of you know about the expired domain name services. They offer stuff like

a) list of domain names that will expire the "next days"
b) list of domain names that expired "today"

I'm wondering how they do that? is this solved with the update protocoll of the dns service?

if no: how
if yes: how do i configure a dns server able to get this update packages for such a big zone?!

But before you answer:
yes, i'm quite new on that subject and i will be thankfull for a answer that will show me the direction.

They do it like this:

1) they download the actual zone file for a given TLD - like .COM for example. They get this file from the company that manages all .COM domains in the dns.

2) They write a script to go through and make whois queries for each domain in the massive zone file to the appropriate TLD domain registry. The registry has status information on all domains.

3) They compile the results into some sort of database for your viewing pleasure.

thank you for your answer. but i'm wondering if it isn't possible to receive update dns packages for really expired domains.

as i know rfc 2136 is handling this topic, but i don't know if it is possible to get this notification. or better: if it is worth working on this topic.

rfc 2136 has to do with dynamic update which has nothing to do with notification of expiring domains.

"I'm wondering if it isn't possible to receive update dns packages for really expired domains."

hrm? I just told ya how.