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

From: James Kempf <[email-masked]>
Date: Wed, 25 Apr 2001 09:57:22 -0700 (PDT)

Raj,

>What we do not want to see is another IN (Intelligent network) type of
>solution,
>and cram a lot of smarts about mobility and optimization in the network by
>introducing multiple levels of smart routers/agents. After all "the stupid
>network"
>does have it's merits :)
>There are enough compelling reasons to add one LMM agent, but more than
>one ....? Or let's put it this way, how many levels of hierarchy would be
>optimal?
>
>So if we were to deploy this solution (since we agree that the issue is one
>of 
>deployment) today, how would you propose changing existing routers in the
>operator's network which may have to become mobility aware? You could
>potentially
>add one more new router/LMM into the network quite easily as opposed to 
>introducing new functionality into an operator's existing network and
>equipment.
>

I guess I don't understand your response. Nobody's proposing an IN like
solution. The RR proposal has hierarchy, it is not all that much
more complicated than HMIP, IMHO.

All that we're asking for is that the requirements state that the
solution SHOULD (not MUST) support multiple levels of LMM agents.
The reason is so that if a network operator has a deployment situation
where the signalling lines get long, they can deploy an upper level
agent to keep the external CoA fixed.

People are reading too much into "LMM" and "hierarchy" as words.

		jak

---

From: Erik Nordmark <[email-masked]>
Date: Thu, 26 Apr 2001 02:06:55 -0700 (PDT)

> agent to keep the external CoA fixed.

I still don't have a picture that tells me what you gain.
I assume keeping the external COA fixed is not a goal in itself - the
goal is just better performance (less signalling over long paths).

So if the signalling lines (e.g. between different metropolitan areas,
different small countries, or different topological clouds that don't follow
any geographic notion like metro or country) are long then you can just have
one LMM per such cloud without any hierarchy.
Thus movement between clouds cause the home agent and 
correspondents to be updated.

In this case when a mobile moves within the cloud (e.g. one metro)
there is only local signalling, and the movement between clouds 
the boundaries between the clouds in the operator's network have
been designed so that the movement between them is infrequent.

When would you need another level of hierarchy?

Or stated differently, if you place the LMMs so that the latency over the
wired part of the network between the MNs and their LMM is on the order
of 10 ms, and let the HA then it seems like for it to make sense to have 
another level of hierachy below it that level should be two orders of magnitude
of delay less i.e. on the order of .1 ms. Thus speed of light in copper/glass
would limit that to 20-30km in size. Sure, you could argue that you need an
additional level for each factor 3 or 10 in the latency domain, but my
personal gut feel is that in such a case you are adding complexity for little
performance gain, especially given that any signalling involving the MN will
add on the order of 50 ms of delay due to the coding necessary to deal with
the fading.

   Erik

---

From: Jim Bound <[email-masked]>
Date: Thu, 26 Apr 2001 11:08:46 -0400 (EDT)

Erik,

The metro networks are good example of the need for hiearchy.  The metro
is not a clean cloud with perfect routing core and edges at all at least
today, In addition there are ILECs under the metro core that will begin to
support mobility esp for phones and pda's under the ILECs are the LACs and
then under that VPN networks.  If I roam around all day at ILEC1 within
LACs having a distributed LMM hierarchy permits me to not bother the metro
HA.  I am assuming IPv6 or Global IPv4 Addresses above too.

/jim