Date: 18 Jan 2001 09:01:14 -0000
From: "D. J. Bernstein" <[EMAIL PROTECTED]>
Message-ID: <[EMAIL PROTECTED]>
| Is there some other claimed benefit of A6?
It is certainly possible to set up some horrid indirections which
cause lots of extra work with A6, as it is with NS or MX.
However, in all of those cases, the indirection, if used
intelligently (and I would admit that there isn't a lot of
intelligence in a lot of DNS configuration) allows significant
caching benefits - especially when addresses are likely to
change, and changing addresses is supposed to be one of the
things that IPv6 makes easy (which includes cheaper).
That is, with
$ORIGIN my.domain
host1 604800 IN A6 64 <mac> pfx.my.domain.
host2 604800 IN A6 64 <mac> pfx.my.domain.
(etc)
pfx 7200 IN A6 0 <prefix1>
7200 IN A6 0 <prefix2>
The mac addresses of host1 & host2 can stay cached for ages
(if I ever change one, I can just retain the old address as
an alias long enough for the old A6 record to expire), whereas
the prefix needs to be refreshed quite frequently.
With A6, any refresh of the prefix will refresh it for all the
hosts that use it.
The same applies to NS records, MX records, etc - those records
typically have values that rarely need to change, but the
associated addresses change often. But many hosts can share
the same MX, and many domains the same NS, refreshing the
A record for any of them in the cache refreshes for all of
them.
kre
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