On Fri, Feb 22, 2013 at 10:06 PM, Ole Troan <[email protected]> wrote:

> > IPv6 Host H1 will receive two PIO's, one each from R1 and R2, with
> > autoconfiguration and on-link flags set, and configure /64 prefixes from
> > both provider 1 and provider 2 (RFC 2461 4.6.2) and it will know these
> > as being on-link.
> >
> > But IMHO there's no further AS number/provider information/upstream
> > topology information coupled to these /64 prefixes. There might be a
> > router-router interconnect LAN between R1 and R2, or there might not be.
>
> if there is no interconnect between R1 and R2, then the host has two
> interfaces connected to two separate connections. then I can't see how
> that can be solved in the network. my assumption is that all homenet
> routers must be connected (I see I haven't stated that anywhere, but that
> should be added).
>

Do we really need this?

When I originally put together the strawman it seemed to me that there are
only two cases: either the two border routers have a path to each other, or
they don't. If they do not have a path to each other, then the host cannot
be connected to both routers using the same interface - because if it is,
it's a broadcast interface and those two routers are also connected to each
other.

Should we write this in the draft?


> > How will the host H1 know to associate source address prefixes from
> > provider2 with router2 for off link destinations e.g. to a Provider2/56
> > or Provider2/32?
>
> in your case it will RFC6724, rule 5.5
>

You don't need to invoke RFC 6724 for this. RFC 3484 (prefer outgoing
interface) is enough. We should put this in the draft though.

> My expected host behavior would currently be that it'd just choose one
> > of the known available default routers from the list. If correct fine.
> > If not, then wait for an ICMPv6 redirect to be told to use the other
> router.
>
> you would only get that if the routers were connected of course.
> whichever came first, you'd either get a unreachable code 5 (wrong source)
> or ICMP redirect, or the router would just forward the packet to second
> router.
>

Please let's not design something that requires ICMP redirects to work. It
will be slow and unreliable.


> > Thus H1 should never send packets with a source address derived from a
> > PIO received in an RA from R2, to a potential default router R1 that
> > sent an RA message but did not include a PIO for this particular source
> > prefix?
> >
> > Where is this behavior defined in an RFC? I don't see it in
> > http://www.ietf.org/rfc/rfc2461.txt Section 4.2 or
> > http://tools.ietf.org/html/rfc4862#page-18
> > In fact section 6.3.6. on default router selection is quite explicit and
> > doesn't mention associating potential default routers with prefix
> > information options at all AFAIK.
>
> again, that's rule 5.5 (which is somewhat weak) in 6724.
>

3484 rule 5 too, right? Or not?
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