[dns-operations] resolver cache question

[Mark Allman]

>> [1] https://www.sciencedirect.com/science/article/abs/pii/S1389128620312627
>
> This is a network security paper, not a systems engineering
> paper. The authors are primarily concerned with the storage
> requirements of systems that store DNS data well beyond the
> nominal TTL of the RRsets, which they want to reduce by filtering
> out "disposable" records.

Sure.  There are multiple goals.  The logging goal is a little weird
as motivation to my eye.  In any case, there are other papers, too.

> As far as detecting whether "clogging" of DNS resolver caches
> occurs, it probably would make sense to have resolvers increment a
> "premature expiration" counter when they expire cache entries
> prior to the scheduled TTD of the cached RRset or cached
> message. This would allow operators to provide feedback to
> resolver developers as to whether this behavior is actually
> occurring in the real world. (Looking at the unbound-control
> manpage I don't think unbound has such a metric, not to pick on
> unbound.)

I was sort of hoping this kind of thing was logged and folks could
give me a clue with actual data.  Seems like a natural thing to log.
But, I guess not.  Or, maybe folks are not willing to share.

Thanks!

allman
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