Subject: RE: Comments and questions on dns-discovery

From: [email-masked]
Date: Wed, 24 Jul 2002 14:18:55 +0300

Hi Erik,

>    The mechanism described here is to be used as a last 
> resort, when no other configuration information is available.
> 
> Does this mean that implementations of this mechanism MUST also
> implement another mechanism, such as DHCP, for discovering the DNS
> servers?
> If not, the above words have little practical meaning since an
> implementation which only supported this mechanism would be compliant;
> the mechanism would be the "only" resort i.e. both the first 
> and last resort.

There is always manual configuration or some proprietary configuration
method (for example some sort of 'over the air' configuration for 
cell phones using SMS).  Anyhow, isn't an implementation decision
on what to implement and what not to?  All we can do is make recommendations
on what implementations should do.

John

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From: Erik Nordmark <[email-masked]>
Date: Thu, 25 Jul 2002 01:56:44 +0200 (CEST)

> on what implementations should do.

If part of evaluating the applicability of dns-discovery
is based on it being mandated to be the last resort, then it
seems like there had better be a standard non-last resort which
is tried before the last resort. Otherwise the statement about "last resort"
is vacuous and should be removed from the document.

Assuming that the statement stays in the document ...
Saying that devices which implement DNS discovery MUST also implement
a manual configuration method, and only if that manually configured
stuff is not set (or fails?) does it fall back to using dns-discovery, would
give some meaning to "last resort".
But that would place a rather strict requirement on minimal IPv6
implementations since they would need a mechanism to enter the manual
information. While cell phones might have ways to manually configuring this
that doesn't require a user keying in IPv6 addresses on a keypad, an
IPv6 toaster doesn't have such a mechanism.
Hence for some devices it might make more sense to require DHCP as the
non-last resort.

So perhaps requiring either a DHCP method or a manual configuration
(where the latter might imply a keypad) is the way to provide 
meaning to "last resort".

   Erik