[dns-operations] How does resolver query works

[InterNetX - Marco Schrieck]

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Hi all,

thank you for your answer, but what happend in the case of an "timeout"
or "connection refused" on a single IP.



Am 13.03.10 00:40, schrieb Mark Andrews:
> 
> In message <20100312123933.GB42913 at macbook.catpipe.net>, Phil Regnauld writes:
>> Paul Vixie (vixie) writes:
>>>
>>> what bind4/bind8 did and what i still think is the right thing, is to build
>>> the list of nameserver addresses (unrolling all the nameserver names), and
>>> try them in measured-RTT order, assuming 0 RTT for untried addresses, and
>>> depref'ing each address a little when rolling in new RTT samples.
>>>
>>> on SERVFAIL or REFUSED, the address is poisoned (given an absurdly long
>>> artificial RTT) along with all other addresses that came from the same
>>> nameserver name.

As I understand that If one "nameservername" send send servfail then
bind try also the other one?

>>
>> 	So what does BIND9 do ?
>  
> It translates the names to addresses then sorts the list of addresses
> based on rtt.  Addresses without a rtt estimate get a small random
> value.  It does this using the current cache contents.  It will
> also lookup addresses for nameservers it doesn't have in parallel
> to completing the current query.  If it has no addresses it will
> stall waiting for the nameserver's addresses to resolve.
> 

Regards

Marco
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