Well, not always bad but sometimes.
A friend of mine who works on DNSBLs wrote yesterday (quite by
coincidence, unware that there's a meeting this week) asking if anyone has
thought about this problem: DNSBLs have the same form as rDNS, IPv4 names
all start with four labels containing digits, IPv6 names start with
sixteen single character hex digit labels. In nearly every case the
entire DNSBL is in a single zone so minimization wastes a lot of queries
crawling down the zone. Queries to DNSBLs are fairly randomly distributed
so 8020 doesn't help much. If a cache gets to a point where the remaining
labels look like this, it is almost certainly rDNS or a DNSBL and the
cache should stop crawling and send the full query.
I'd like to write a draft that updates RFC 9156 by describing situations
like this that caches could recognize and avoid useless churn, added to
section 2.3 which already suggests special casing underscored labels.
There are probably others I haven't thought of; who's done research on this?
Regards,
John Levine, [email protected], Taughannock Networks, Trumansburg NY
Please consider the environment before reading this e-mail. https://jl.ly
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