forwarding algorithm and timeouts

Kevin Darcy kcd at
Wed Mar 28 00:03:25 UTC 2001

Brad Knowles wrote:

> At 2:55 PM -0500 3/27/01, Kevin Darcy wrote:
> >  Well, this is just a matter of semantics, but when a nameserver program (like
> >  "named") forwards, it is acting in the *role* of a "resolver" (i.e. a
> >  DNS client). It is therefore quite reasonable, in my opinion, to compare and
> >  contrast, as Bob is doing, the respective timeout/retry strategies for
> >  "forwarding" versus stub resolvers.
>         These are technical terms, and the correct one should be used to
> describe the behaviour in question.

Well, *technically* the term "resolver" covers any software program or component
which acts as a client to extract DNS information. The components of "named" which
answer queries directly from cache or authoritative data are
"nameserver" components; the component of "named" which queries other nameservers,
is a "resolver" component. In fact, I'd go so far as to say that when named is
forwarding in "forward only" mode, it is effectively functioning as a "stub"
resolver, since it's using no iteration-and-referral logic and (therefore) the
servers it uses recursively are predefined in its configuration. The only
difference is that, unlike most stub resolvers, "named"s resolver component will
cache answers.

> >  This just sounds wrong. What about forwarder failover or the RTT-based
> >  forwarder-selection in BIND 8.2.3? Perhaps you are using terms like
> >  "contact" in a way that is unfamiliar to me.
>         This is what was recently confirmed to me by Jim.  Now, maybe I
> misunderstood what he was saying, but this is my understanding.

I suspect a miscommunication of some sort.

- Kevin

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