[122448] in North American Network Operators' Group
Re: Time out for a terminology check--"resolver" vs "server".
daemon@ATHENA.MIT.EDU (Larry Sheldon)
Sun Feb 14 20:20:22 2010
Date: Sun, 14 Feb 2010 19:19:59 -0600
From: Larry Sheldon <LarrySheldon@cox.net>
CC: "nanog@nanog.org" <nanog@nanog.org>
In-Reply-To: <f1dedf9c1002141621q24c67ce6ra6e5441ea605bb7d@mail.gmail.com>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On 2/14/2010 6:21 PM, Scott Howard wrote:
> 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.
That is another piece that I had glossed over--the "client" side of a
server.
>
> 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.
Calling any form of server a "resolver" seems new to me--or my lack of
understanding is older that I like to admit.
>
> 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).
Seems like TTL management would take care of that but I think the issues
of recursion are now different from the safe world I thought I lived in
20 years ago.
Thanks.
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