Subject: RE: Usefulness of automating policy tables (was RE: draft-cpatel-ipv6-automated-policy-table-cfg-00.txt)

From: "Chirayu Patel" <[email-masked]>
Date: Thu, 21 Aug 2003 16:32:59 +0530

> If the order of the addresses matters to any significant degree, no matter
> who
> decides what that order is or what mechanism is used to set that ordering,
> it
> will hamper applications.  So I don't see it as useful to build mechanisms
> to
> allow sites to set that ordering.  It's solving the wrong problem, and it's
> encouraging people to try to juggle address ordering for whatever purpose
> they
> might think is useful, which in turn makes life for apps more difficult.

As you might have noticed, I have just started wading into the IPv6 waters.
This hard line view, considering that address selection in IPv6 is an rfc, was
quite unexpected. :-)

Can you refer me to any drafts/papers/emails/examples that illustrate the cons
of address selection? I have been through the archives, but apart from a lot
of arguments, I failed to find any examples that show the harm address
selection can cause vis-à-vis other methods.

> It is not acceptable to expect distributed apps to use DNS for lookups.
> DNS is too slow and too unreliable and too out of sync with the real world
> for some applications.

Ok. If your apps are using IP addresses, then they can use the same (dest)
address (and bypass address selection) from all locations and all will work as
usual. IMHO, modifying the precedence of the prefix in the policy tables
will/should not result in parts of the network becoming "not reachable".

CP

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From: Keith Moore <[email-masked]>
Date: Thu, 21 Aug 2003 09:37:51 -0400

> selection can cause vis-à-vis other methods.

I'm writing one.

> will/should not result in parts of the network becoming "not reachable".

there are two reasons this will not work:

1. if any of the addresses used are link local addresses, those will not work
from a different link.  (the same was true of site local addresses, but there
was consensus to deprecate them)

2. with v4 networks, people are accustomed to having "private addresses" which,
because they are ambiguous, cannot be routed outside of the local network.
people believe they need those for security reasons.  so now some of the IPv6
people are saying that since v6 does not have private addresses (nor site-local
addresses, which were close to the same thing), sites will acquire unique
address blocks and filter them at their borders, and set up services so that
some hosts would only accept traffic on those "local" addresses.  so the
host or application would have to choose the "right" address in order to
access those services or hosts.