[v6ops] ULA and IPv4 - draft-liu-v6ops-ula-usage-analysis

Christopher Palmer <Christopher.Palmer@microsoft.com> Tue, 05 November 2013 02:50 UTC

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From: Christopher Palmer <Christopher.Palmer@microsoft.com>
To: "v6ops@ietf.org" <v6ops@ietf.org>
Thread-Topic: ULA and IPv4 - draft-liu-v6ops-ula-usage-analysis
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Date: Tue, 5 Nov 2013 02:50:27 +0000
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Subject: [v6ops] ULA and IPv4 - draft-liu-v6ops-ula-usage-analysis
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Section 3.3 of the draft:


"  As described in section 2.2.2 of [RFC5220]<http://tools.ietf.org/html/rfc5220#section-2.2.2>.2>, when an enterprise has

   IPv4 Internet connectivity but does not yet have IPv6 Internet

   connectivity, then the enterprise chose ULA for site-local IPv6

   connectivity. Each employee host will have both an IPv4 global or

   private address and a ULA. Here, when this host tries to connect to

   an outside node that has registered both A and AAAA records in the



   DNS, the host will choose AAAA as the destination address and the ULA

   for the source address according to the IPv6 preference of the

   default address selection policy [RFC3484<http://tools.ietf.org/html/rfc3484>]4>]. This will clearly result
   in a connection failure."

This is only true if the ULA is configured on a host that also has a default route The enterprise can avoid any issues by simply configuring a scoped route on hosts (say, only for the ULA prefix). If a network does not provide connectivity to the IPv6 Internet, it should not advertise ::/0.

I think it's useful to discuss that configuration route, which is possible today with a vast majority of hosts and just works.

Modifying the prefix policy table is not suitable at scale. And the DNS preference logic alluded to in section 3.3 is highly ambiguous.