Subject: RE: Comments and questions on dns-discovery

From: [email-masked]
Date: Thu, 25 Jul 2002 10:49:10 +0300

Hi Eric,

> 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.

Well, either we should remove it, or add clarification on why
it should be a last resort (see further comments below).
 
> 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".

I agree.

> 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.

I think that text that states either DHCP or manual configuration MUST
be supported would be best.
 
> 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".

Should we do this in this document, or elsewhere?  My thinking is 
that text along the lines of:

  This mechanism is not meant as a primary means for obtaining DNS 
  addresses and should be used as backup.  DHCP and/or manual 
  configuration are recommended as primary mechanisms.

And then in some document (perhaps the node requirements) we could
have text discussing what is mandated, etc.

John

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From: Erik Nordmark <[email-masked]>
Date: Fri, 26 Jul 2002 00:06:01 +0200 (CEST)

> have text discussing what is mandated, etc.

I think each specification should clearly state interrelationships
that are local to this specification. For instance, if you implement the foo
spec you MUST implement the mechanism to secure it with IPsec.
We shouldn't punt such constraints to a node requirements document.
Instead the node requirement should talk about which specifications are
required, and conditional requirements between them. For instance,
if you implement RFC X you MUST implement RFC y as well.

  Erik