Subject: [Seamoby] CAR discovery

From: [email-masked]
Date: Tue, 26 Mar 2002 11:56:52 -0500

Hi all,

the recent discussion on CAR discovery gave me the impression that
there is some disconnection regarding the scope of CAR discovery.

You should keep in mind that CAR discovery is not dealing with final handover
decisions, it merely determines a set of geographically adjacent access routers that satifies MN's requirements at the time of requesting this 
information. Whether to use this set of ARs or not for the final decision, 
is up to the algorithm that does that decision. Said algorithm is called 
TAR selection and is out of scope of the CAR discovery work. 

However, for the openness of implementing any kind of TAR selection
schemes, the current requirements take care of this by demanding
the usability of CAR information by others (see exact wording in
the document). With that requirement, CAR discovery solutions must
enable to implement ANY kind of TAR selection, whether AR- or
MN-based. Hence, it does really not matter whether the final
authority of selection is the MN or any other network-related
entity, since this question is simply out of scope.

Regarding the requirements for CAR discovery, we therefore should
allow any kind of CAR discovery solutions as well, as long as they 
fulfill the basic job requirements, namely providing said set of CARs 
(under several constraints, such as preserving existing security models). Hence, any solution, either MN-based, AR-based, network-assisted, or 
whatever, should be feasible with the requirements, even though some 
people might not believe that certain solutions are possible or sufficient. Keep in mind that the best proof is the assessment of a provided solution. 

Hence, I still hope that the final requirements won't preclude
certain solutions by demanding certain functionality to be located
in certain entities.

Thanks,

Dirk

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From: "James Kempf" <[email-masked]>
Date: Tue, 26 Mar 2002 12:32:21 -0800

> (under several constraints, such as preserving existing security
models). Hence, any solution, either MN-based, AR-based,
network-assisted, or
> people might not believe that certain solutions are possible or
sufficient. Keep in mind that the best proof is the assessment of a
provided solution.

Sorry, Dirk, but I thought we settled this in Minneapolis.

The point of requirements is to constrain the solution set sufficiently
that the selected solution solves the problem in a way that makes
engineering sense. I have not yet heard an argument as to why AR-based
CAR discovery makes engineering sense.

If you think the requirements should allow that possibility, then please
give me an argument why.

        jak

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From: "James Kempf" <[email-masked]>
Date: Tue, 26 Mar 2002 12:32:21 -0800

jak

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From: "Henrik Levkowetz" <[email-masked]>
Date: Tue, 26 Mar 2002 23:24:09 +0100

> entity, since this question is simply out of scope.

Mmm, maybe the point which needs to be made here is that any list of
GAARs which could be assembled by a particular network or AP may be
incomplete, and the only entity in a position to determine the
relevant list of GAARs, and from there the CARs, will be the MN. So
I believe this non-commital formulation of the process may actually
be harmful.

The operators of any particular access technology network will of
course attempt to optimize the use of their network, and network
directed handovers *whithin one access technology network* will be
taken care of by that network, but the MN cannot even afford to
believe that a particular network may not discriminate against
others in its presentation of GAARs (although we should define
a protocol which does not encourage such discrimination). So the
MN should be the central point, already in the GAAR determination.

	Regards,
		Henrik

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From: "Henrik Levkowetz" <[email-masked]>
Date: Tue, 26 Mar 2002 23:24:09 +0100

Regards,
		Henrik