One problem with using the same link address is that there
will often be
more than one router on the last hop, for redundency. One
could of course
use the same set of link addresses, but it is a bit of a
hack, as Julien has
indicated.
jak
----- Original Message -----
From: "Christian Vogt" <chvogt tm.uka.de>
To: "James Kempf" <kempfdocomolabs-usa.com>;
<Mohan.Parthasarathynokia.com>; <vidyanqualcomm.com>;
<gerardo.giarettatelecomitalia.it>; "Genadi
Velev"
<Genadi.Veleveu.panasonic.com>
Cc: <netlmmngnet.it>
Sent: Wednesday, March 15, 2006 5:42 AM
Subject: Re: Default Router in NETLMM (was RE: [netlmm] New
I-D: Security
Threats to NETLMM)
> The benefits of DNA are, in fact, minor if ARs use
different link-local
> source addresses. As Mohan said, MNs would simply
record a new AR in
> their default-router lists, but they would stick to the
current, stale
> default router until NUD reveals the unreachability.
>
> As a result of NUD, the old AR's NC entry would then
be deleted, so the
> MN would select a new AR according to section 6.3.6,
"Default Router
> Selection", in RFC2461bis. But even then is it
not guaranteed that it
> will select *the* (most recently discovered) new AR.
>
> The single benefit of DNA, in this situation, is that
the MN sets its NC
> entry for the new AR to REACHABLE state due to the
received *unicast*
> RA. With RFC2461bis, the new AR's NC entry is always
set to STALE
> state, regardless of whether the RA was received by
unicast or
> multicast. Consequently, the new AR is in a better
position if DNA is
> used.
>
> But what's wrong with using the same link-layer
addresses for all ARs?
> (I wrote this in my email from March 12, but it was
apparently lost in
> the noise.) If you use the same link-layer addresses,
DNA *does*
> provide a huge benefit: When the MN receives a L2
trigger, it does the
> RS/unicast-RA exchange, leaves the Default Router List
untouched
> (because the AR's link-local address did not change),
updates its NC
> entry for the AR to the new AR's MAC address, and sets
the NC entry's
> state to REACHABLE. All further packets will hence go
via the new AR
> without delay. This should work--- without NUD, BTW.
Plus, you can use
> different MAC addresses for different ARs.
>
> Regards,
> - Christian
>
> PS: I did not read Julian and Sathya's on the MN-AR
interface, which
> James mentioned. Maybe, their approach is similar...
>
> --
> Christian Vogt, Institute of Telematics, Universitaet
Karlsruhe (TH)
> www.tm.uka.de/~chvogt/pubkey/
>
>
> James Kempf wrote:
>> Why would the MN continue to use the old router
when it has no
>> confirmation of reachability? I have not looked at
the DNA draft lately,
>> but it seems to me that this is the whole point of
DNA.
>>
>> jak
>
>
>
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