[clue-tech] DNS

[Will]

The DNS RFC is very vague on how a Resolver should treat temporary errors so
further investigation of each implementation is needed.

See Page 30 of RFC 1034
http://www.ietf.org/rfc/rfc1034.txt

"5.2.3. Temporary failures

In a less than perfect world, all resolvers will occasionally be unable
to resolve a particular request.  This condition can be caused by a
resolver which becomes separated from the rest of the network due to a
link failure or gateway problem, or less often by coincident failure or
unavailability of all servers for a particular domain.

It is essential that this sort of condition should not be signalled as a
name or data not present error to applications.  This sort of behavior
is annoying to humans, and can wreak havoc when mail systems use the
DNS.

While in some cases it is possible to deal with such a temporary problem
by blocking the request indefinitely, this is usually not a good choice,
particularly when the client is a server process that could move on to
other tasks.  The recommended solution is to always have temporary
failure as one of the possible results of a resolver function, even
though this may make emulation of existing HOSTS.TXT functions more
difficult."



On Thu, Nov 18, 2010 at 1:18 PM, Chris Ernst <penguin-guy at comcast.net>wrote:

> It's up to the client.  Typically, if the initial request fails and
> there is another NS record, it will just try the next one.
>
>        - Chris
>
> On 11/18/2010 12:56 PM, David L. Willson wrote:
> > If a domain has a couple NS records setup at the registrar, what happens
> > if one of name-servers is down? Do lookups fail back to the client or
> > fail gracefully to the other NS with no notice to the client?
> >
> > What if there are more than two name-servers? Are they all tried before
> > a failure is reported, or just a certain number?
> >
> > What if the name-server is up, but there's another sort of failure, like
> > "no such domain" or something like that?
> >
> > I am willing and able to look this up myself, or trace it out myself,
> > but I'm short of time, so I thought I'd check if someone knew off the
> > top of their head, and wanted to show off a bit.
> >
> > David L. Willson
> > Trainer, Engineer, Enthusiast
> > MCT MCSE Network+ A+ Linux+ LPIC-1 NovellCLA UbuntuCP
> > tel://720.333.LANS
> > Freeing the world from the tyranny (or whatevery) of Microsofty-ness
> >
> >
> >
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