Re: Caching SERVFAIL?

On Fri, May 8, 2009 at 1:03 PM, Peter Dambier <[email protected]> wrote:
> My experience with caching SERVFAIL, I lost connectivity for a day.
>
> From time to time but at least once per day my isp is breaking my aDSL session.
>
> When my router does not reconnect fast enough or when there is an outage
> all queries will fail and get cached. After about 10 minutes the internet
> is dead for the rest of the day. Of coarse killing dnscache works much
> faster.
>
> Cheers
> Peter

Yes, due to scenarios like this, I'm not in a hurry to start caching
SERVFAIL.  RFC2308 section 7.1 says

    In either case a resolver MAY cache a server failure response.  If it
    does so it MUST NOT cache it for longer than five (5) minutes, and it
    MUST be cached against the specific query tuple <query name, type,
    class, server IP address>.

I think 5 minutes is waaaay to long.  I'd tend towards less than 30 seconds.