On Wed, 12 Aug 2015, Ole Troan wrote:
Mikael,
in the land of contrived examples! :-)
this working groups answer to the below is make this a homenet and run HNCP.
then the host rule enhancement isn’t used.
in any case let me try to reply below, although I’m quite confused about the
example.
two PIO’s of different length on the link sounds like a configuration error.
Then I must still be missing something.
Example time:
A B+-+F
+ +
| |
+----+-----+----+
| |
+ +
C D
+
|
+
E
A, B and D are routers. A has received a /56 from ISPA. D has been delegated a
/64 from this ISPA prefix using DHCPv6 IA_PD. A is advertising a /64 from ISPA
with A=1,L=1, and also advertises M=1 for the ABCD link. A is also advertising
ISPA /56 as off-link to indicate that it'll handle the entire /56.
currently, advertising a PIO with L=0 isn’t a routing advertisement (“handle
the prefix”?). it only affects a hosts prefix list and how it does onlink
determination for addresses in that prefix. i.e. a host would first chose D and
NH, then find a suitable source.
with the new rule, the PIO becomes more like a source constrained route. “for
any source address matching prefix in PIO, send traffic to me”.
I don’t understand what you would gain from the ISPA/56 PIO over the ISPA/64
you’d have in C already.
Because the DHCPv6 IA_NAs handed out to C (by A or a DHCPv6 server on the
ABCD link) isn't in any on-link PIO. So without the /56, C has no idea it
needs to send these packets to A to avoid BCP38 filtering (in case for
instance B is announcing ISPB prefixes).
Now, do we want D to do anything to tell C that E is reachable through
D? Like announce in RAs an off-link /64? Or announce an RIO? Or do
nothing and let all traffic from C to D bounce via A? Do we want A to
in some way announce the delegated /64 IA_PD prefix?
1) run homenet / routing protocol
That won't tell C anything, but ok, fine.
2) absolutely not
3) RIO with router lifetime of 0 could work but geez this is what homenet solves
4) yes
5) no
What do we want A to do, should it announce the /120 as off-link? On-link might
make sense in this case.
that would only affect hosts on the ABCD link. D would still send all traffic
for the /120 to A (as default route)
Yes.
I don’t see that you need either.
How will C know whereto send packets sourced from its IA_NA address?
/64 on-link PIO from A for the on-link ABCD /64 prefix
yes.
/120 on-link PIO from A for the on-link ABCD DHCPv6 IA_NA prefix
possibly. probably not needed.
How will C know whereto send packets sourced from its IA_NA address?
As far as I can tell, you need either covering /56 or announcing the /120
(remember, this /120 it not within a /64 that there is a PIO for if you
don't announce the /56 as an L=0 PIO).
Again, my problem is that I don't see how IA_NA (or IA_PD in case it's a
router) outside encompassing PIO can get correctly routed. And again, this
is a valid deployment scenario. So either we say "MUST announce PIO with
L=0 or L=1 for all addresses that a host will have, or things will not
work".
I also want to be able to solve RFC7084-style DHCPv6 IA_PD requesting
router to send packets from hosts behind it to the correct upstream, so I
would like this case adressed as well.
Announcing the entire PIO /56 L=0 that the A router has been delegated
would solve this problem, yes? And if there is a /56 and /64 that are
overlapping, do longest prefix matching on the PIO and choose that NH.
--
Mikael Abrahamsson email: swm...@swm.pp.se
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