Subject: RE: [seamoby] Micromobility Problem Statement ISSUE 2

From: "Gary Kenward" <[email-masked]>
Date: Wed, 3 Jan 2001 17:43:53 -0500

Well stated Phil.

At the very least, the suite of IP mobility solutions should not impose
topology restrictions - such as the number of hops between the MIP
mobility agents and the AP - upon the network. 

Gary

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]]
> Sent: Wednesday, January 03, 2001 12:10 PM
> To: [email-masked]
> Subject: [seamoby] Micromobility Problem Statement ISSUE 2
> 
> 
> 
> 
> 
> In IPv6 or IPv4 networks, the mobility agents are probably 2+ hops up
> stream in the router chain inside a given administrative domain.  Many
> quick decisions must be made in milliseconds with respect to handoff
> and mobility.  The Mobile node, and the access point/router have a
> better perspective on the local traffic situation (QoS), security, and
> compression, etc.  Thus, these devices are in the best position to
> make decisions  about adding links, m-casting, context transfer etc.
> Furthermre, this implies that the  SeaMoby protocol should reside in
> MNs, and AP/Rs and work in conjunction with MIPv4 or MIPv6 when
> subnet routing boundaries are crossed.   This also has the desirable
> effect of moving intelligence to the "edge" where we can avoid
> redundancy and assure global scalability.
> 
> 
>

---

From: Pat Calhoun <[email-masked]>
Date: Thu, 4 Jan 2001 17:12:58 -0800 (PST)

> mobility agents and the AP - upon the network. 
ok, so it looks like we are heading in a general direction. I do find Phil's
comments most interesting, but of course we cannot, in seamoby, redo layer 1
functions over IP (but perhaps someone should be looking at this). In any
case, one "problem" with micro-mobility are the number of hops between the
mobile and the mobility agent. 

Mobile IP restricts the number of hops to one. So an AP, in the traditional
802.11 sense, that acts as a bridge can allow Mobile IP to work through it,
assuming that a Foreign Agent is on the wired subnet. However, such an AP
working as a "router" would not work, since the Mobility Agents would not be
forwarded on the wireless link.

One discussion that I brought up in the paging sublist to describe a problem
where paging may be useful, in probably in fact a micro-mobility problem and
not a paging one (as James Kempf pointed out).

Here is the problem:

Imagine two wireless networks, each with their own AP. Each AP has two or more
Foreign Agents on the wired side to support the mobile nodes on the wireless
nets. Now let's assume that a mobile is on wireless net A, and is using
Foreign Agent X (on Net A). The mobile node moves to Net B, and the AP is
notified of the transition. Now the AP must somehow notify the FA of the
existence of the mobile. There is currently no protocol to do this. In the
cdma-2000 world, a bastardized version of Mobile IP is used (called the RP
interface). However, if such an environment needs to be supported, something
is required.

Now, whether or not the AP acts as a bridge, or a router, using the above
scenario, let's assume that the FA is (somehow) notified of the new mobile's
presence, and it finds out that the mobile moved from the AP on Net A. How
would the Foreign Agent know *which* FA supported the mobile on Net A? Looks
like something is required there.

I suppose the following questions should be asked:
1. Can we safely assume that Mobile IP is used on the mobile? I would hope
that the answer is yes, given that some mobility protocol needs to be
designed, and I would hate to have to go through the same History the MIP WG
went through :) if so,
2. Do we even care about a standardized protocol between the AP and the FA
3. Is a protocol required to locate the FA handling a particular mobile?

So are the above two points what Micro-mobility is all about?

PatC

---

From: Pat Calhoun <[email-masked]>
Date: Fri, 5 Jan 2001 11:10:15 -0800 (PST)

> Hi Pat,
> 
> Regarding the load balancing problem you describe, it appears to me 
> that it is neither a micro-mobility or paging problem - it is a load
> balancing problem that could be resolved locally at the original FA site
> (the new AP/FA sends the message towards ONE of the old AP/FAs -
> the old FA or a director at that site forwards it to the correct
> old FA - similar in flavor to some web load balancing solutions). 
> 
> Just my thoughts...

I actually agree with this train of thought. However, doesn't the redirector
at the old FA's subnet need some similar protocol to find the FA responsible
for the mobile node? It seems that whether the new FA needs to find the
mobile, or some redirector on the old subnet, something is required.

Or am I offbase?

PatC

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From: Ramachandran Ramjee <[email-masked]>
Date: Fri, 05 Jan 2001 19:06:37 +0000

Hi Pat,

Just my thoughts...

Cheers,
Ram

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From: Ramachandran Ramjee <[email-masked]>
Date: Fri, 05 Jan 2001 19:50:52 +0000

> mobile, or some redirector on the old subnet, something is required.

Pat,

I think you have several questions in there..

1) The question of a redirector finding an FA out of several - a
mechanism is needed but it could be something implementation specific...
for example, an FA could be allocated based on a hash of the
mobile's HA address etc. Not convinced we need a protocol and
that too, a standardized protocol, since it is local to one FA site.

2) The question of old FA finding the mobile  - now, that I think
is a paging problem.

3) The question of new FA finding the old FA (or old redirector) - this
is needed only when the new FA gets only a L2 update and needs to 
translate it to an L3 old FA address - this is really an optimization
to avoid paging and I think it doesn't belong in seamoby.

Cheers,
Ram

---

From: Pat Calhoun <[email-masked]>
Date: Fri, 5 Jan 2001 14:37:07 -0800 (PST)

> to avoid paging and I think it doesn't belong in seamoby.

But the example provided is where the AP is NOT the FA, and it must signal
link layer events over IP (similar to CDMA2000 R-P interface). If there are
many FAs assigned to each AP, how does an FA know which FA for a given AP it
should contact to perform the handoff?

In source triggered events, that is simple since the source Foreign Agent
would get a signal that the mobile is moving to a new "cell". However, for
target triggered events, this is much more complicated since there are more
than one FA on the old AP's net to worry about.

Hence the problem (assuming the above is a problem that even needs to be
solved). Again, I am just trying to understand that Micro-Mobility really is
all about (in the context of SeaMoby, of course).

PatC