Re: VeriSign's rapid DNS updates in .com/.net

[Duane Wessels <cee4 () packet-pushers com>]

> If a zone owner lowers a TTL and causes an increase in load, most of
> the foot being shot off is his or her own: the zone's own name servers
> will bear the brunt of the increased query load.

Maybe, but don't forget that when BIND9 and DJBDNS caches find
expired nameserver address (A) records they don't trust any cached
data and start them back at the roots.  And in the case of BIND9,
it sends both A and A6 queries for each nameserver in the list.

For example, microsoft.com's five nameservers have A records with
TTL of one hour.  Worst case we might expect every BIND9 cache to
send 10 queries to the roots (then the TLDs) every hour, just for
these nameserver addresses.

Duane W.