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List:       namedroppers
Subject:    mdns configuration / .local.arpa. namespace definition
From:       Aidan Williams <Aidan_Williams-A15677 () email ! mot ! com>
Date:       2001-08-25 1:59:44
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Bernard Aboba wrote:
> Good point. My understanding was that configuration is attempting to
> provide the following information:
> 
> a. Whether mDNS is to be used at all.
> b. If it is to be used, the order in which it is used relative to other
>    alternatives (e.g. unicast DNS first, then mDNS)
> c. For the future, it would be useful to be able to control the scope
>    used in mDNS (e.g. linklocal vs. wider scope). This isn't something
>    we care about now, but the configuration choice we make shouldn't
>    preclude this down the road.
> 

An observation: none of this configuration relates to the DNS
namespace(s) themselves, just to the way they are looked up.

Therefore, I am not in favour of overloading the DNS search list so
that an entry of .local.arpa. means "use multicast" for DNS requests.
Keeping the above configuration information away from the DNS
searchlist is a good idea.

So far, I haven't seen a clear description of the characteristics of
the .local.arpa. namespace itself.  Most discussion of it seems to be
related to turning off/on multicast lookups.

I see the namespace like this:

  - The .local.arpa. suffix is *not* globally unique.
    (a nice clear definition of this somewhere would be a good thing)

  - The .local.arpa. namespace is analogous to link-local, site-local
    or rfc1928 addressing.

  - The .local.arpa. namespace is useful independently of whether
    multicast lookups are used.  Is there a good reason to preclude
    unicast lookup in this namespace?

A standard configured DNS server could use these local names
(one could imagine entries like pop3, smtp, etc in there).

It could be a sensible default place to put non-global scoped address
mappings.

Zeroconf networks (which may not have a global DNS suffix) can use
this suffix too.

regards
	aidan
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