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

Scott Howard scott at doc.net.au
Mon Feb 15 00:21:46 UTC 2010

A "resolver" is basically a client.

There's two types of resolvers - recursive resolvers (that look after
doing the full resolution themselves - starting at the root servers
and working down), and "stub resolvers" which are only smart enough
pass the entire request onto another server to handle.

On most system, the "code in your local machine" will be a stub
resolver. That's why you need to configure it to point to another
server that looks after the actual recursion for you.

The "DNS Server" running at your ISP that your stub resolver connects
to is acting as both a server (to accept requests from your client),
and as a resolver (to actually resolve those requests), and almost
certainly also as a cache for results.  For simplicity, many people
simply refer to them as Resolvers, whilst others call them Recursive
servers or Caching servers.

The server actually answering the requests for your domain is an
Authoritative Server. An Authorative-only server doesn't ever act as a
client, so it isn't a resolver.

It is possibly to run both Authoritative and Recursive server on the
same IP, but it's generally not recommended for many reasons (the most
simple being that of stale data if your server is no longer the
correct nameserver for a domain, but it's still configured to be
authoritative for that domain).


On Sun, Feb 14, 2010 at 4:02 PM, Larry Sheldon <LarrySheldon at cox.net> 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?
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