Subject: RE: Multiple Levels of LMM agents (was: RE: [mobile-ip] Revised L ocalized Mobility Management Requirement s)

From: James Kempf <[email-masked]>
Date: Tue, 24 Apr 2001 08:55:21 -0700 (PDT)

Hi Erik,

>> Ulimately, the issue is one of deployment. The worst possible case
>> is we cycle an LMM protocol without multiple levels of hierarchy
>> to proposed and discover during deployment that we need it. 
>
>Jim,
>
>You are stating the design philosophy that leads to kitchen sink
>protocols - put in as much as possible to make sure nothing we can
>ever imagine has been left out.
>
>I much prefer the opposite philosophy - only include what we know for 
>sure will be needed.
>

Actually, no. I'm saying that we have had at least three people who
have given good arguments, IMHO, as to why multiple levels of
hierarchy might be needed. On the other side, those arguments
are refuted by two people who think that no hierarchy is needed.
Neither side is going to convince the other, both sides have
good arguments.

The kitchen sink results when somebody says "let's put in this neat
feature," then somebody else says "let's put in this neat feature,"
and the group iterates on this for several rounds with nobody 
really coming up with good arguments for or against the feature except
that it was X's idea.

What I'm saying is that we have some arguments the feature is needed,
so let's put it in. From Karim's last email, it sounds like we can
probably accommodate his concerns about multiplying failure possibilities.
If we don't put it in and deployment proves that we need it, as I and
at least two other people on the list think will likely be the case, we
are stuck with going back through proposed standard. 

		jak

---

From: Charlie Perkins <[email-masked]>
Date: Tue, 24 Apr 2001 10:08:24 -0700

Hello James and Erik,

The point of hierarchy is to localize the signaling.  That's a good
feature.  It also has the advantage of reducing signaling across
administrative boundaries.  Both of these are valuable for scalability.
Furthermore, I think that proper design will see to it that not
much complexity is added.  The reason for this is that the
regional-aware routers act "enough" like home agents that
almost the same protocol works.  I think even HMIP could
be made to work with hierarchy; the restriction seems purely
artificial.

Adding features for special cases can be good or bad.  However
that isn't what is happening here.  It's almost like removing restrictions
to allow more general operation.  That's not a kitchen-sink approach.

Regards,
Charlie P.