Time out for a terminology check--"resolver" vs "server".

Larry Sheldon LarrySheldon at cox.net
Sun Feb 14 19:12:43 CST 2010


On 2/14/2010 6:10 PM, Rob Austein wrote:
> At Sun, 14 Feb 2010 18:02:48 -0600, Laurence F Sheldon, Jr  wrote:
>>
>> I thought I understood but from recent contexts here it is clear that I
>> do not.
>>
>> I thought a resolver was code in your local machine that provide
>> hostname (FQDN?), given address; or address, given host name (with
>> assists to build FQDN).
>>
>> And I thought a "server" was a separate program, might be on the same
>> machine, might be on another machine (might be on the local net, might
>> be distant) that the resolver code called for information that was not
>> in local cache.
>>
>> Just what is the straight scoop?
> 
> No doubt Olafur will beat me up yet again for not having written the
> DNS lexicon years ago, but:
> 
> - A "resolver" is something that implements the "resolver" (ie,
>   client) role in the DNS protocol.  It might be a stub resolver, the
>   client side of a recursive nameserver, a pure iterative resolver,
>   ....
> 
>   The defining characteristic is that it send queries (QR=0) and
>   receives responses (QR=1).
> 
> - A "name sever" is something that implements the "nameserver" (ie,
>   server) role in the DNS protocol.  It might be an authoritative
>   nameserver, the server side of a recursive nameserver, ....
> 
>   The defining characteristic is that it receives queries (QR=0) and
>   sends responses (QR=1).
> 
> Clear enough?

Yes--tracks with what I thought, pretty much--I was missing the
clientness of the resolver code to go with the serverness of the server.

> Mapping protocol definitions onto the plethora of terms used by
> operators in the field is left as an exercise for the reader, no
> sarcasm intended.  DNS is an old protocol, there are an awful lot of
> people who think they understand it, 

I am one of those is sure he understands it--which belief crumbles when
I try to explain it to somebody else.

and each of those people has
> their own set of terms that they're comfortable using.  The
> definitions above are what I rammed through the IETF during several
> rounds of standards writing, but I would be the first to admit that
> not everybody uses the terms the same way as I do.

DNS arcana is one of the things that somebody should document on the
internet-history list while there are still people around who can do so
with some authority.

Thanks.
-- 
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