I've done quite a bit of searching over the archives and over various
web resources, but I haven't seen this issue addressed directly.
Apologies if I've just missed it.
RFC 3484 ("Default Address Selection for Internet Protocol version 6
(IPv6)") section 5 gives a set of ordered comparisons for source
address selection. However, missing from this list is a distinction
implied by RFCs 2461 and 2462: some systems may have a mix of
addresses acquired by stateless address autoconfiguration, stateful
(DHCPv6) configuration, and manual addressing. How are these
distinguished?
Rule 7 does address the temporary (RFC 3041) addresses, but what about
these other flavors of addresses? Are they distinguished only by
scope?
Was this issue addressed and intentionally omitted from the RFC? (If
so, I don't see it in the archives.)
I suspect that some clients may need to distinguish among the various
flavors here. I'd suggest amending Rule 7 to read:
Rule 7: Prefer stable, public addresses.
If SA is a manually-configured address and SB is automatic or
temporary, then prefer SA. If SA is automatically configured via
stateful (DHCPv6) methods and SB is automatically configured via
stateless methods or temporary, then prefer SA. If SA is
automatically configured via stateless methods and SB is temporary,
prefer SA.
Similarly, if SB is a manually-configured address and SA is not,
then prefer SB. If SB is stateful and SA is stateless or
temporary, prefer SB. If SB is stateless and SA is temporary,
prefer SB.
When the application has the "prefer temporary address" flag
enabled, all temporary addresses are (within this rule) elevated in
preference above manually-configured addresses. The other
preferences are unaltered. (In other words, the preference order
with this flag set becomes temporary first, then manual, stateful,
and stateless last.)
... or, to simplify, defining a "stability_of_address(A)" function
that can work here.
--
James Carlson, KISS Network <[EMAIL PROTECTED]>
Sun Microsystems / 1 Network Drive 71.232W Vox +1 781 442 2084
MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677
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