Subject: Re: [mobile-ip] Some Analysis

From: James Kempf <[email-masked]>
Date: Tue, 1 May 2001 09:14:07 -0700 (PDT)

Hi Wolfgang,

Just one comment.

>Let me finish by giving my peronal interpretation of these numbers
>(and I would be very happy to receive critical replies):
>Hierarchical mobility support is, in some cases, provably better
>than the non-hierarchical counterpart.
>But these cases do not occur very often.
>Hence it is questionable to attempt an optimization -
>it would have an effect only in rare cases.

Indeed, that's the question, isn't it? How common are these cases going
to be? I think we can argue about light years v.s. millimeters and
60 ms v.s. 6, but we can't know really. It is a judgement call.

One thing is for sure. If hierarchy is not supported, then these
cases become suboptimal. And, to the extent that these cases correspond
to particular business models, any decision we make on not supporting
hierarchy will result in an adverse impact on those business models.

		jak

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From: Wolfgang Schoenfeld <[email-masked]>
Date: Wed, 02 May 2001 15:25:27 +0200

Hi Jak,

the business model surely plays an important role
when the effect of hierarchies is investigated.

> hierarchy will result in an adverse impact on those business models.

If you travel slowly (e.g. by feet),
there is great chance that your moves
result in topologically (in the sense of the network) small steps
where optimization by hierarchy has an effect on the number of BUs.
On the other hand, if you travel by plane,
you will cover in each step topologically long distances
where the difference between the hierarchical 
and the non-hierarchical solution vanishes.
I.e. hierarchical support makes sense
for pedestrians and not so much for airmen.

(Please, all readers of this mailing list should remember that
this is meant only in the context of my simple "wheel" model.
No general statement is implied
because this depends on many more details.)

Wolfgang

-- 
Wolfgang Schoenfeld, GMD-IPSI, Dolivostr. 15, D-64293 Darmstadt
Office: +49-6151-869-865 FAX: -6847 Mobile: +49-174-7093455