ietf-mxcomp
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Re: DOC-BUG/TECH-OMISSION in -protocol: A vs AAAA

2004-09-05 16:28:16

On Mon, 06 Sep 2004 00:00:24 +0200, Peter Koch
<pk(_at_)techfak(_dot_)uni-bielefeld(_dot_)de> wrote:

o In 4.3, although the mechanism is called "a", suggesting similarity to
  the IPv4 address RR type "A" combined with the "Note" in 3.1 both A and
  AAAA RR types need to be checked, don't they?

Interesting.  Now that you've pointed it out, I think there might be
an ambiguity.  In particular, I always assumed that, for example,
"a/24" meant check IPv4, while "a//64" meant check IPv6, and just "a"
meant check both (same as "a/32//128").

But I guess it might be possible to interpret "a/24" as equivalent to
"a/24//128" and "a//64" as equivalent to "a/32//128".  In fact,
reading section 4 pedantically, I think that may be the more exact
interpretation.  This is slightly annoying, because it would have been
nice to have a mechanism to restrict a particular use of the mechanism
to IPv4 or IPv6.

In fact, while we are nitpicking, the capitalization of "cidr-length"
is not consistent.  Section 4 uses CIDR-length, while 4.6 uses
"cidr-length".    Moreover, that term is never formally defined. 
Therefore, in addition to fixing the ambiguity above, I also propose
the following change to section 4.6.  Change:

   If the cidr-length is omitted, the ip4-cidr-length is taken to be
   "/32" and the ip6-cidr-length is taken to be "/128".

To:

   If ip4-cidr-length is omitted, it is taken to be "/32".  If
   ip6-cidr-length is omitted, it is taken to be "/128".

In fact, it's probably too late for this, but I wonder if for
consistency the grammar shouldn't have been:

      IP6             = "ip6" ":" ip6-network [ "/" ip6-cidr-length ]

and the default "//128".

David


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