Subject: [seamoby] A 'Psuedo' MM Problem Statement draft

From: [email-masked]
Date: Fri, 2 Mar 2001 12:45:46 +0200

Hi all,

All of the various mails back and forth have actually been very productive
(for me).  I think a good number of points.  I've attempted to summarize
some of the better points bellow.  This is a psuedo-draft - meaning that if
I've made any sense in my points below, I shall try to insert the sensible
words into the next revision of the MM problem draft.  I'd like to thank all
of the persons whose email messages I've plagerized.

John

=================================

Why Micromobility

The Internet scales well with clients, servers, and peers using the same IP
address while connected to the Internet.   The Internet works by addressing
devices at the edge of the network, not in the middle of the network.
Mobile clients, servers, and peers should operate the same way.  What is the
best way the Internet can support mobile clients, servers, and peers while
maintaining the same scalability allowed by the current internet
architecture?

Capacity: A Sea of Mobile Nodes 

The Internet is being more and more wireless - or to put it another way,
users should be able to connect to the Internet via fixed lines or
wirelessly.  More wireless nodes, moving about will create more demand for
capacity.

One method to achieve higher capacity and/or higher access speeds in a
wireless network is through the reduction of cell sizes (micro-cells,
pico-cells, nano-cells ...). One can imagine a scenario where each office
has its series of base stations (access points), offering tens to hundreds
of megabits per second of wireless access. These type of pico-cellular
environments must ultimately compete with wireline LAN service quality,
costs, security, and plug-and-play scalability.

Having smaller cells with higher access speeds also means higher
requirements from the mobility management protocols. This naturally due to
the fact that as cells become smaller (i.e. access point density increases),
handover rates and thus also the associated signaling loads will increase.
The mobility management protocol must allow seamless mobility, i.e. the
ability of the network to support fast handoff (low delay) between base
stations, with minimum or zero packet loss (smooth handoff).  In this
setting, it is important to minimize the associated signaling in order to
ensure that the signaling does not interfer with user data.

What About Mobile IP

Mobile IP mainly solves the macro-mobility management problem. It has been
widely stated (even in RFC 2005) that Mobile IP is not a suitable protocol
to handle micro-mobility management. The inefficiency of Mobile IP in
micro-cell environments can be attributable to the fact that Mobile IP is an
end-to-end delivery protocol, where only the CN and HA adjust to the
movement of a MN. This involves signaling only between endpoints and results
in slow adjustments to the movement of a MN. Thus Mobile IP works best when
the MN does not change its link-layer connections very often - which is not
true for micro-environments. However, in response to the desire to push
Mobile IP down to the access, there are various research activities that
investigate the possibility of enhancing the Mobile IP functionality to
support micro-mobility.

In the words of the tallest MIP designer:

It is easy to understand "well, we can make Mobile IP do that"... And I
don't think it's necessarily an unfortunate thing that people are thinking
about such things.  But, on the other hand, it's important to avoid protocol
bloat and unnecessary requirements.  To me that just means that good
engineering is required.

Philosophic Conundrum: Hierarchy or end-to-end?

Mobile IP is a known protocol.  It has been implemented and seeing
deployments.  Certain optimizations are being developed to insure
performance and scalability.  There are a number of papers showing the
applicability of Mobile IP to a range of applications.

However, fixing the transport path for a MN at various points only
introduces more opportunity for failure while possibly improving handover
speed but not guaranteeing an improvement in handover.  Peer to Peer
addressability is the only scalable technique for large scale mobility.
Addressing various middleman routers increases the latency because optimal
paths may not be used and decreases reliability because a stateful single
point of failure is introduced into the network.  If any hierarchy is needed
then it should only be introduced temporarily for the duration of a handoff
between ALn and ALn+1 where the MN IP address changes.  If the MN IP address
does not change then hierarchy is not needed.  Maintaining network
intelligence outside of handover window introduces unnecessary complexity in
the routing path and unreliability.

A Sea of Protocols & a Head full of Aches

All of this may be solvable, if this was the only problem.  Howover, routing
is seldom an application.  A user may be using connection-oriented protocols
on top of IP, connection less protocols on top of IP, QoS protocols,
security protocols, AAA protocols and so on.  As most of these protocols
have been designed with the end-to-end concept in mind, mobility and
frequent routable IP address changes may inflict much extra signaling and a
greater probability that the user may not get the expected results

Possible Way Forward

One question is whether another routing protocol for mobility is required.
Presently we have the MIP and the Manet routing approaches (Tunneling vs.
host based routing).  It may be so that a new routing protocol is not
needed, but there may be work needed to support _signaling_ a router that it
needs to change how a subnet is reachable. It is quite possible that the
heavy lifting can already be done by current protocols, and that all we need
is the ability to trigger them to happen. You might call that a "routing
protocol" too, but it ought not evoke the fear and loathing that postulating
a Routing Protocol should.

Bottom Line

SeaMoby should study solutions and determine if a protocol that enables
local routability with better latency characteristics, in addition to the
global association managed by Mobile IP is the proper approach to solving
the problem.

---

From: "Phillip Neumiller" <[email-masked]>
Date: Fri, 2 Mar 2001 10:00:35 -0600

Hats off John very nice summary.

-pdn

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From: Peter Lei <[email-masked]>
Date: Fri, 02 Mar 2001 10:33:03 -0600

John,

Nice summary...

> end-to-end delivery protocol, where only the CN and HA adjust to the
                                      ^^^^
> movement of a MN. 

This doesn't read clearly/correctly to me... I think this should say
"where the HA and/or CN must adjust to each movement of a MN" (via
end-to-end signaling such as binding updates...).

Thanks!
--peter

> This involves signaling only between endpoints and results