Re: forward-last and a BIND question.

[Mark.Andrews@nominum.com]

	The fall back can be triggered on the existance of address
	records for the other family and -ve answers for the addresses
	family supported by the server.

	Mark

> Mark,
> 
> 1. After having thought some more about this, I really do not think
>    that a configuration based upon a static, address based
>    identification of a translator will work out.
> 
> I.e. something a la 
> 
>         options {
>                 ...
>                 forward-last { 3ffe:507:1ff:2:240:96ff:fe34:bc64; };
>         };
> 
>    My first objection is that as soon as we start using *addresses*
>    under someone elses control in configuration files we are on the
>    wrong train in general. Its bad enouogh to have addresses in DNS
>    data, but in config files is even worse. Just imagine a helpdesk at
>    an ISP trying to specify the a new v6 address by phone.
> 
>    My second objection is that an address is to restricted. A name
>    would have among other properties the ability to point to several
>    addresses, which I think will be an important feature.
> 
>    I understand that you were concerned about priming of the system
>    and presumably the present code does it all at startup before
>    lookup service is available. But still, I wonder whether it would
>    be possible shange this into a lazy evaluation of the forwarder so
>    that we could keep it as a name.
> 
> 2. It will be needed to provide translator service in both directions
>    at some point in time. Regardless of how much people are urged to
>    keep all DNS data available over v4 transport we will see a mix of
>    all three variants (v4, v4+v6 and v6).
> 
>    Therefore, obviously, this will get a bit complicated since BIND
>    will have to divide its forwarders into two sets depending on the
>    direction of translation that is needed and the type of stack that
>    is available at the local machine when glue of the wrong type is
>    encountered.
> 
> 3. A question: what happens if there is both A and A6 glue for
>    ns.foo.bar.org and they expire from my cache at different times? 
> 
>    As far as I understand there is no way of knowing that something
>    may have been lost, so I will simply assume that I can only reach
>    ns.foo.bar.org over f.i. v4 transport although in fact v6 is
>    available. Hence I will (being v6-only) go through a translator,
>    even though it really isn't necessary.
> 
> I think we will have to live with the translator model for a *very*
> long time and therefore we should look at it more carefully than would
> be needed for a quick hack.
> 
> Johan
> 
--
Mark Andrews, Nominum Inc.
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark.Andrews@nominum.com