[bind10-dev] About resolver Negative Cache Design

[Shane Kerr]

Michael,

On Fri, 2011-02-18 at 17:54 -0600, Michael Graff wrote:
> On 2011-02-18 5:51 PM, Jerry Scharf wrote:
> > Depending on the situation, I have seen 10-40% negative answers on
> > recursive servers. One survey respondent said he had 40% NXDOMs alone.
> > Others may have different numbers. So negative answers are very common
> > in the real world. This is also a reason why people want to add negative
> > entries that last more than 10 minutes (like forever.)
> 
> They say they want that, then we get people who ask us why a name fails
> even when it has been changed in their DNS.  Not everyone gets how
> negative caching works today.  I would be very worried about a "forever"
> negative entry.
> 
> How many of those NXDOMAIN entries were for AAAA records btw?  I know
> those are usually NODATA/NOANSWER form of negative caching, but I wonder.

A lot of these may be for black-hole lookups (anti-spam stuff). Those
generate a lot of negative answers.

--
Shane