In article <[email protected]> you write: >Folks- > >I just finished reading a paper that basically tries to figure out >if a hostname is worth caching or not [1]. ...
I can't give you a direct answer but the same question arose a while back when we were thinking about DNSBLs for IPv6 addresses. The obvious approach is a variant of rDNS so every IP address corresponds to a different DNSBL name, and it occurred to us that someone trying to avoid filtering could hop to a different IP address for every message, causing a whole lot of one time DNS lookups. I came up with a different design that more or less published a B-tree of IP CIDR ranges in the DNS, so all lookups within the same range would reuse the same answer. I did some modelling and the answer was a loud who cares. Even with IPv4 addresses about half of DNSBL lookups are never reused, and it's never been a problem. The only papers I could find on DNS cache performance were very old, back in the day when a megabyte was a whole lot of memory. I agree that this is indeed a non-problem. To the extent that it is a problem, the random names come from a small set of actors (Google Chrome, we're looking at you) and if you care, you're better off with special cases for the known problem makers. R's, John _______________________________________________ dns-operations mailing list [email protected] https://lists.dns-oarc.net/mailman/listinfo/dns-operations
