RE: address selection and DHCPv6

[Lawrence Zou <zou.rong at huawei.com>]

I don't think we should amending rule 7 in such a way.
 in fact , i think this will make the rule 8 unworkable.
according to RFC3484,when at last we have two source address
available,both can pass rule1-rule7,then,the rule 8 
will chose the longest match prefix.but if we amend rule 7 and prefer
manul-configured address,some thing changed,for example:
address A is autoconfigured  and belong to ISP1,host use it to access
network of ISP1.
address B is manuconfigured and belong to ISP2,host use it to access
network of ISP2.
then if we prefer manuconfigured address ,we will chose address B as
source when we access ISP1,that maybe refused by the PE router of ISP1
for the reason of soure address filter.


Best regards,

Lawrence  

>-----Original Message-----
>From: James Carlson [mailto:james.d.carlson at sun.com] 
>Sent: Wednesday, October 25, 2006 3:52 AM
>To: ipv6 at ietf.org
>Subject: address selection and DHCPv6
>
>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                    
><james.d.carlson at sun.com>
>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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