[dns-operations] caches only resetting TTL? was Re: Where to find "DNS resolution path corruption"?

[Paul Vixie]

> I'd like to have it written up, regardless of venue.

i'll get right on that.

> One observation is that the private label (non-BIND) caching recursive
> nameserver (paul, do you have any shorthand name for it ?) you refer to will
> encounter some domains like co.uk, com and net with a high frequency of
> changing SOA serials. The high frequency, plus the high level domain the
> frequency applies to, makes the nameserver to prune a lot. Would it, in
> those case, be configurable to not cache for these domains at all? Do you
> have any statistics on how often that logic path is hit ?

it's actually a lazy prune, since heap deallocation is expensive.  if the
SOA has been seen to increase, cached negname or negdata is deleted when
encountered.  so, new names and rrsets coming into existence will be seen,
old names and rrsets going out of existence still have to time out normally.
(however, i don't think this level of detail is important for an RFC writeup.)