Subject: [mobile-ip] The link-local address issue

From: "Hesham Soliman (EAB)" <[email-masked]>
Date: Mon, 15 Jul 2002 09:04:50 +0200

Jari asked me to send this to the list so we don't 
forget. 

The problem I'm thinking of is related to the link-local
address in the MN. Currently IPv6 implementations have one
link-local address. If there is a collision on a visited 
link (rare but possible) then the MN might do what 2462
says (wait for reconfiguration, which is too drastic)
or generate a new iid. If it does the latter then it is 
likely to delete the link-local address. This could be a 
problem when the MN goes home and attempts to deregister 
with its link local address. 
So it might be best to recommend that the MN keeps 
track of its 'Home link-local address' (new!). 

Alternatively, the MN can deregister with its global home address?
But I didn't think about this last alternative. 
We can talk about it in the meeting. 

Hesham

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From: Francis Dupont <[email-masked]>
Date: Mon, 15 Jul 2002 09:52:46 +0200

=> we have to wait for the DAD/DIIDD resolution but in some cases
IMHO it can be a good idea to use a RFC 3041 address:
 - no interference with the HA "address protection"
 - the collision case is handled in a reasonable way
 - privacy is better (i.e., get a new RFC 3041 when the link changes)
Of course, it works better if the layer 2 says the link can have changed...

=> urgh!

=> it can if there is no strange game with the neighbor discovery.

=> I believe we should wait for the IPv6 WG in order to do the work
only once (to go back to my first statement).

Regards

[email-masked]

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From: Jari Arkko <[email-masked]>
Date: Fri, 26 Jul 2002 12:30:47 +0300

Perhaps someone could tell me why the DAD vs. DIIDD question
has relevance for this discussion? It seems to me that since the
link local prefix is the same in all locations, DAD vs. DIIDD
doesn't affect the behavior for link-local addresses. That is,
if the mobile node waits for reconfiguration after a collision,
it will do so for the address that is used both as a home and
foreign link-local address. But maybe I'm missing something...

If not, then I think the right thing to do would be to have the

MIPv6 specification require "resetting" all ND information
upon movement. That is, we'd forget the fact that we had collisions
in a previous location. We'd also forget the fact that we did
DAD for an address in the previous location, and would be
forced to do a new DAD... I think this would make the protocols
less vulnerable to local problems, whatever they might be.

Jari

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From: Francis Dupont <[email-masked]>
Date: Sat, 27 Jul 2002 17:39:48 +0200

upon movement.

=> I agree but this should not be bound to MIPv6...

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From: Vladislav Yasevich <[email-masked]>
Date: Mon, 29 Jul 2002 09:30:24 -0400

Yes, I agree.  There was a thread a few months ago about
what to do with NCE on the mobile, but that did not get any
answeres.  It looks like the "resetting" all ND state is
the way to go.

-vlad

> less vulnerable to local problems, whatever they might be.
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Vladislav Yasevich	       Tru64 UNIX - IPv6 Project Lead
Hewlett Packard 	       Tel: (603) 884-1079
Nashua, NH 03062	       ZKO3-3/T07