Subject: [mobile-ip] Meaning of Alternate Care-of Address?

From: "James Kempf" <[email-masked]>
Date: Sun, 17 Feb 2002 11:35:31 -0800

Hi folks,

Hopefullly, I can get some response on this between the excellent but
voluminous MIPv6 security debate.

Section 10.9 of draft-ietf-mobileip-ipv6-15.txt states:

   In any Binding Update
   sent by a mobile node, the care-of address (either the Source Address
   in the packet's IPv6 header or the Care-of Address in the Alternate
   Care-of Address Sub-Option of the Binding Update) MUST be set to one
   of the care-of addresses currently in use by the mobile node or to
   the mobile node's home address.

What does "in use" mean?

For example, in MIPv4, a non CoCoA is "in use" by the MN even though the
MN never
configures an interface actively because the FA is managing the CoA.

Because MIPv6 has CoCoA exclusively, one would think that "in use" means
"the MN has a network interface configured with the address," but that
rules out some interesting applications. Suppose, for example, I want to
hand off from my cell phone to my workstation when I walk into the
office, and turn the cell phone off. I might like to implement this so
that the workstation registers an alternate CoA for the cell phone's
home address (presuming both the cell phone and the workstation have the
same trust relationship with the HA). But, if the alternate CoA is
restricted to being on the same host, then this application would be
impossible.

Comments?

                jak

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From: Greg Daley <[email-masked]>
Date: Mon, 18 Feb 2002 08:41:30 +1100

Hi James, 
	quick answer below.

>    the mobile node's home address.

In Hierarchical MIPv6, the Regional Care of Address (RCoA) is an
address either of the MAP (Extended mode) or on a network adjacent
to the map (Basic mode).

This is present as the Alt-CoA in some binding updates (to HA/CNs).

Additionally, the local host should be to configure this address
(In basic mode) as a local address (maybe /128), but not in extended
mode.

I'm not about to comment on usage scenarios, but the Address does
not have to be a locally configured interface address, but one valid to
use
(for example, in conjunction with HMIPv6);

		Greg