Slashdot Mirror
Mirror Listings Though TXT DNS Records?
mackman asks: "I was wondering if anyone has ever though about using their DNS servers to provide mirror information? A specially formated TXT-record could easily provide a DNS-cache-friendly mirror listing. A TXT-record would just need a list of servers and paths, or perhaps a more complicated mapping for servers which only mirror a subset of the original site. This would allow for much more flexibility than a basic round-robin A-record scheme. For example, instead of pounding the Red Hat web server to get a mirror listing (or relying on Slashdot posts for that matter), why not do a 'dig -t txt mirrors.redhat.com'? Of course we could build this into download managers like wget."
DNS is designed to be an extensible, flexible, distributed, and massively scaleable lookup database. It is quite suited to what you propose, and has certainly been used for much lamer ideas already.
I wouldn't use TXT records, though. SRV records might be more appropriate, but people are apparently using SRV for LDAP nowadays so you're probably better off just defining a new type. Use the procedure laid out in the RFCs for designating a new type of "experimental" DNS record, so that everyone will be compatible with you (well, everyone that follows the RFCs, anyway, which might leave out MS and DJB) or figure out how to use one of the obsolete record types.
You can look at some of the other types of records in RFCs 1035, 1183, 1706, 1886, 2672, 2782, and 2874. Most of the important ones (well, other than IPv6 stuff) are in RFC1035.
Incidentally, you're going to get dozens (if not hundreds) of posts here that will say "You shouldn't do that with DNS!". Pretty much any question you ask around here that even mentions DNS will get the same result, so just ignore them. I think these people are a lot more interested in shooting down ideas than in actually testing them, which is the only real way to find out if they will work.