Subject: [mobile-ip] LMM draft comments

From: "Alan O'Neill" <[email-masked]>
Date: Sat, 20 Jul 2002 05:52:55 -0400

Hi Carl,

Here is some input into the LMM requirements draft.

An additional requirement into LMM is the ability to aggregate as well as
localise hand-off for multiple HoAs. A MN that has more than one HoA
presently has to update multiple global HAs in parallel on each hand-off
because traditional MIP signalling is HoA specific. If LMM only addresses
localisation then each local hand-off will still need to be replicated.
Multiple HoAs is a requirement in 3G and non-MIP mechanisms are presently
used for LMM in 3G to enable a MN to hand-off all its concurrent sessions at
once (RNC relocation etc). LMM needs to reproduce this capability so that
the MN can use LMM aggregate signalling to avoid sending multiple parallel
hand-off signals. 

One obvious use for two HoAs is that one is used for global remote access
(inter-domain mobility) and one for local access (intra-domain mobility).
This enables a foreign operator to sell optimised Internet access via LMM
whilst in addition scalably supporting a users corporate access. I would
therefore also further suggest an additional requirement should be that LMM
mechanisms be able to support both local and remote services. As both local
and remote services are on the MN and both use MIP, not considering or
including this capability in the requirements is I think a hole.

Additional motivation for LMM is that of operator decoupling. If a MN is in
a foreign domain then the hand-off performance in that foreign domain should
not / must not be dependent on the availability and dimensioning of links
and nodes, including the global HA, in a different domain. LMM serves to
ensure that the foreign domain is solely in a position to decide the
performance of the hand-off. This is particularly important as HAs become
increasingly deployed into  SMEs and home networks, potentially over
on-demand links.

Introduction
Bottom page 2 it states that binding updates during RO are issued by the MN
which is an MIPv6 specific comment. In MIPv4 they are issued by the HA. I
would instead generalise this statement to simply say an authorized MIP node
issues the BU..

Terminology - wrt Nested MIP
 I am a little concerned about the use of the term 'coverage area' which may
easily be confused with L2 wireless use of 'coverage area'. The Local
Coverage Area is called a Region in Nested MIP (local mobility region - the
region of local mobility) and the specific Local Mobility Agents are a local
HA (also known as the Regional Mobility Agent) and the access routers (FA in
v4). The term global HA is used therefore to distinguish it from the local
HA. I am however happy to accept the terminology in LMM for the purposes of
the LMM draft, but the particular terminology in Nested MIP is I feel better
suited to the centralised topology in that solution. I hope that that is ok
with you. You may however wish to update the LMM terminology in the light of
these comments.

3.4.3 "The LMM framework MUST NOT create single points of failure in the
network.  The current access router would be excluded from this
requirement."

The global and local HAs assigned to this MN must also be excluded from this
requirement. However, a better to way to describe the requirement might be
to simply state that the solution must have minimal, preferably zero impact
on the availability of the MN / global HA / CN traffic and signalling.

NEW  3.4.9 The LMM framework must ensure that the LMAs can be placed so as
to avoid locations that are bandwdith constrained or costly, and which
minimise signalling and packet redirection over such links. Such a
requirement is critical given the topologies in cellular systems whereby
basestations are typically connected to the core network over expensive
links.

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