Subject: [Ieprep] RE: Folts' stated requirements: mobility

From: Fred Baker <[email-masked]>
Date: Thu, 04 Apr 2002 15:57:25 -0800

At 02:28 PM 4/4/2002, Folts, Harold wrote:
>Do these examples help?

not really. You state that the US Government is interested in the ETS 
having an attribute called "mobility".

What do you want to be mobile? Is this a handset question? Is this a 
question of occasionally moving laptops? Is this a question of being able 
to bring in an internet-on-wheels comparable to the Mobile Telephone 
Networks' Cell-on-wheels?

When you say "mobile", do you mean that the address of the device needs to 
appear to be stationary within some network, although the device is moving 
within an external stationary infrastructure? This is what Mobile IP gives 
you. Do you mean that the corporate/government internal network that the 
device is part of needs to be extensible through an encrypted tunnel to 
make a moving device operationally part of it? That is what an IPSEC of SSH 
VPN would give you. Do you mean that there might be no infrastructure other 
than the internet devices actually there, so they need to be able to 
operationally morph their network topology among themselves as the Army 
WIN-T program envisions? If so, we're discussing mobile ad hoc routing.

I need to understand what you expect to move, and what the ramifications of 
its motion are.

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From: Alistair Munro <[email-masked]>
Date: Fri, 05 Apr 2002 10:07:30 +0100

> [Do the examples from Hal Folts help?] ...not really. You state that the US
> Government is interested in the ETS
> ....

I would expect the bits with antennas to move, i.e. any terminal (handset,
laptop, PDA) and base-station. Depending on the mobility support in the
infrastructure, and whether it is shared or not, there may be no requirement to
change layer 2 or layer 3 interface addresses. E.g. if the service is supported
in a single GSM or TETRA infrastructure (or similar wherever you might be) the
terminal can move anywhere within it without any change of IP address. The
network may be closed/isolated or not.

But this is far too simplistic in my opinion although it would probably be
enough in many situations. If a terminal moves out of its home network then we
are in the mobile IP domain if we want it to keep its permanent address - which
I would say we do if we want to place a call to it peer-to-peer. However, DHCP
and fast DNS update are also solutions with different overheads. This would
apply to terminals that move within range of an agency or ISP WLAN access
point. For the agency case, the terminal may not appear to be mobile, unless it
is roamed in from another agency - mobile-IP again. For the ISP case, we are
back to asking what an ISP would have to do to host emergency calls and
possibly services.

However many applications do not need a permanent IP address - it is a
trade-off between the overheads of mobility management and re-registering your
identity with the necessary services. I suspect security overheads will be
similar in either scheme.

For the case where the whole network is mobile, I think we ought to exclude
this. It is mainly a military requirement.

The case where the emergency services are mobile and installable on demand in a
host network may be quite simple. Mobile-IP, or DHCP/fast DNS update support
the terminals and appropriate security protocols: SSL, IPSEC VPNs do the
protection. DiffServ would have to be enabled - on-demand? (up to the provider
I guess).

I think I am agreeing with Fred's suggestions. At least I feel confident now
that I can do an implementation with these protocols in a purpose built
network.

Personally I think that this is 90% of our job done on what we think the
requirements are, but I still miss thoughts from the agencies, suppliers to and
users of emergency services. Also, mobile-IP may fall into the same category as
multicast - where is the best practice to point people at?

Regards,

Alistair