Trying again on SERVFAIL

[Havard Eidnes]

> Still, being able to differentiate a local network congestion from a
> remote bad configuration would help.

That's true.  There's

  https://tools.ietf.org/html/draft-ietf-dnsop-extended-error-16

which look promising, trying to make it possible to distinguish
between the various reasons a recursor might choose to return a
SERVFAIL response.  It uses an EDNS option to communicate the
additional information.

As for its implementation status in general or in BIND in
particular I'll admit that I don't know off-hand.

Regards,

- Håvard