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

From: "Hesham Soliman (ERA)" <[email-masked]>
Date: Wed, 25 Apr 2001 01:36:07 +0200

Hello Theo,

> Not sure that you have read  either my previous postings and of course underlying
> reasoning on this topic.
> 
	=> Yes I have. I thought I included it in the discussion.

> The size of the domain is something that is not cast in stone. It is expressed as the
> growth in network infrastructure that maps to an individual ISP. The world expects
> that ISPs will grow larger in that sense by populating the routing fabring with more
> and more routing elements...
> 
	=> The size of a LMM domain (or MAP domain or GMA domain) is 
	restricted to how much traffic the top LMM agent can handle.
	This is orthogonal to how big an ISP is. There is no need 
	to assume that an ISP domain = LMM domain. Actually for a
	very large ISP this is probably not possible.

> yes you "guessed" right....SCALABILITY...
> 
	=> Could you explain scalability of what ?
	It's certainly not the scalability of the amount of state
	kept in the routers.

	Hesham

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From: Tom Weckström <[email-masked]>
Date: Thu, 26 Apr 2001 10:44:50 +0300 (EET DST)

Hello,

On Wed, 25 Apr 2001, Hesham Soliman  (ERA) wrote:

Hesham >Hello Theo,

Hesham >> The size of the domain is something that is not cast in stone. It is expressed as the
Hesham >> growth in network infrastructure that maps to an individual ISP. The world expects
Hesham >> that ISPs will grow larger in that sense by populating the routing fabring with more
Hesham >> and more routing elements...
Hesham >> 
Hesham >	=> The size of a LMM domain (or MAP domain or GMA domain) is 
Hesham >	restricted to how much traffic the top LMM agent can handle.
Hesham >	This is orthogonal to how big an ISP is. There is no need 
Hesham >	to assume that an ISP domain = LMM domain. Actually for a
Hesham >	very large ISP this is probably not possible.
Hesham >
Hesham >> yes you "guessed" right....SCALABILITY...
Hesham >> 
Hesham >	=> Could you explain scalability of what ?
Hesham >	It's certainly not the scalability of the amount of state
Hesham >	kept in the routers.
Hesham >
Hesham >	Hesham

As I have experienced the scalability benefit of the LMM, it will allow
scalability in the number of MNs moving within the domain through the
reduced signaling.

BR,
-- 
	Tom Weckström		Dynamics group
				Helsinki University of Technology
				[email-masked]
				http://www.cs.hut.fi/Research/Dynamics/

---

From: Erik Nordmark <[email-masked]>
Date: Thu, 26 Apr 2001 07:56:40 -0700 (PDT)

Tom,

> scalability in the number of MNs moving within the domain through the

Do you have example topologies and numbers showing the differences?

   Erik

---

From: Tom Weckström <[email-masked]>
Date: Sat, 28 Apr 2001 18:51:39 +0300

Hi Erik.

Here is an example of benefits that I think cannot be achieved with just
two levels in the hierarchy.

> Do you have example topologies and numbers showing the differences?

Consider you have one level hierarhy with one "element" (I call those
FAs, but they may be called something else in some of the recent drafts
I have not read) in the highest level and N FAs on the lowest level.
Now, let us assume that considering only signaling, this system can
handle k MNs simultaneously. Those MNs are handling, e.g. VoIP calls and
are moving fast, e.g. on a highway. So, with all the VoIP call data and
localized mobility management signaling of the k MobileNodes, the
highest FA is fully employed.

Now, what happens, if we put another level of hierarchy underneath each
FA on the second level? Let us put M FAs under each of the N second
level FAs. We now have: 1. Level: 1 FA, 2. Level: N FAs, 3. Level: M
FAs. Now, the second layer takes signaling burden away from the highest
FA. How much the signaling is localized to the second layer, depends on
the mobility scenarios (aka mobility patterns) of the MNs. The more MNs,
the more signaling, the more the 3rd level helps. 

Additionally, if the same distance d between FAs is kept all the way
through the lowest level of the hierarchy (I am not saying this is wise,
just to simplify), then the  two-level hierarchy covers length of d*N of
the highway and the three level hierarchy covers something like d*M*N.
So, the hierarchy also provides scalability in geographical terms.

What this third level did not change is the amount of signaling per
kilometer on the highway, but the area of fast handoffs was enlarged by
M times. The VoIP data is taking more bandwidth than the signaling data,
so the highest FA could perhaps not take the VoIP traffic load generated
by k*M Mobile Nodes and should thus be updated with faster NICs.

Sorry for not providing any real numbers. Those would have been great,
but I think my time is way too limited for doing such research right
now.

Here are some seed parameters for further analysis in case anyone is
interested:
	- Number of MNs:	k
	- Number of FAs:	1,N,N*M
	- Number of levels in the hierarchy:	H
	- Distances between FAs (FA1 and FA2):	d_1,2
	- Amount of "useful" data traffic per MN:	X bps/MN
	- Amount of MIP signaling generated by an MN:	S bps/MN
	- Universal link speed in the infra:		L bps
	- Mobility patterns:	Not defined
	- Universal link speed over the air:	W bps

I know these could be fed into a network simulator for nice testing with
real numbers, but that is could be a subject of an entire research
project...

Comments? C'mon and shoot my ideas down! ;-)

Regards,
	Tom

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From: Erik Nordmark <[email-masked]>
Date: Mon, 30 Apr 2001 13:58:32 -0700 (PDT)

Tom,

I've think you've just recreated the computer science argument that the
only good answers are 0, 1, or infinity (and in your case you decided that
infinity was the best one).

I think we need an engineering analysis with some real numbers.
To help point out the need for a quantitaive approach 
I've added some comments below.

> So, the hierarchy also provides scalability in geographical terms.

Yes, but there is a difference between d = 10 meters and d = 10 light years.
If d is the latter I wouldn't need to worry about more hierarchy would I?

> by k*M Mobile Nodes and should thus be updated with faster NICs.

What if the needed bandwith exceeds (say) 100 Tbits/s?
I would be hard to construct such a LMM in the near future.

Thus we do collectively need real numbers somehow.

   Erik