On Wed, 6 Jan 2010, Juergen Schoenwaelder wrote:
1) Mandate that the text representation is <SOMETHING>
and never changes after this.
2) Mandate that the text representation is <SOMETHING>
but take into account new WKPs.
3) Mandate that the text representation is <SOMETHING>
but require that external mechanisms help recognize
even dynamically assigned IPv4/IPv6 prefixes.
4) As above, but specify a mandatory external mechanism.
My main interest is textual comparability of addresses coming from
potentially many different sources. If I can compare addresses safely
only if I know some context information communicated out of band or I
have to configure all sources to produce the same, I feel somewhat
uneasy. My preference thus is 1), I might be OK with 2) if the
frequency of the introduction of new WKPs is very small.
While I like to see v4 address in a readable form when its used that
way, I have to say I agree with Jürgen's concerns, especially if the
algorithm was applied to opertor-specific prefixes as well (the tool
would have to have this OOB intelligence).
However, in some cases I'm not sure if comparison equality is really
such a big deal. I don't think there's a way to satisfy both
"embedded v4 readability" and "absolute comparability" so a tradeoff
must be made.
So, I'd actually suggest that we go for 1) or 2) but soften that a
bit, like: "if it is known by some external method that the prefix
includes an IPv4 address, the representation MAY print it in dotted
decimal". With "external method" I'm thinking of either a command-line
argument or application's own logic; I don't see how you could get
that information "dynamically" so that it would be available to
applications (for example, I don't see apps like that using DHCP
information..).
--
Pekka Savola "You each name yourselves king, yet the
Netcore Oy kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings
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