Subject: Re: [MOBILE-IP] handover: proactive versus reactive

From: "[email-masked]" <[email-masked]>
Date: Mon, 1 May 2000 04:30:35 -0700

> >
> > Network access such as 802.11 is a good model, and that should be our
> ultimate
> > target.
>
> No Pat, I am (sort of, albeit a malcontent), a cellular insider, having
> worked in that
> industry for over 12 years.  My feeling is that PPP must be disposed of
> ASAP.
> This is not a very popular opinion among those that do set the standards for
> cellular
> in those groups like 3G.IP, 3GPP, 3GPP2, etc.  I believe we can still rescue
> Bluetooth
> from this "circuit" mind set, by recommending an L2CAP link adaptation for
> IPv4 and
> IPv6 that works precisely like that of 802.11 in the Pittsburgh BOF.
>
Phil, I am a little confused by your response. You open by disagreeing with
me, then you agree with my (that PPP must go).

So, are you of the opinion, as I am, that a circuit switched model for
wireless networks is Really Bad Design (TM).

PatC

---

From: "Andrew T. Campbell" <[email-masked]>
Date: Mon, 1 May 2000 09:44:25 -0700

> wireless networks is Really Bad Design (TM).

The last bastion of "circuit" in wireless networks in the air-interface.
Packets to the BTS is (while still controversial in some quarters) a
given. May be it will fade over the air soon  al la WLANs - but
that will take sometime and more smarts.

The difficulty is control.

If "cicuit==control" then there is no doubt that some level of
"control" is required in wireless networks above and beyond
wireline.

Control is here to stay.

Control can equal state and mechanisms.

A good research question is what is the
minimum amount of state and level of control needed to
allow IP to scale in wireless networks.

That is an open questions and the answer
lies between cellular and packet readio....

Andrew

---

From: Arthur Ross <[email-masked]>
Date: Mon, 1 May 2000 07:19:20 -0700

Once again, RIGHT ON Andrew!

My vote is for some form of SSMA-based packet radio, with power control. It
obviously needs some sort of congestion control at the physical level, but
I think that is quite doable.

How do you define "allow IP to scale"? Complexity? Thermodynamics? Seems to
me that the difficulty lies in the relationship between the two.

A major conceptual leap in the SSMA air interfaces was the notion of tight
closed-loop transmitter power control, including the ability to turn the
power WAY down (CDMA handsets, can and do sometimes transmit less power
than they are receiving). This has a lot to do with scaling at the physical
level. A well-executed CDMA cellular/PCS system, for example, has pretty
much CONSTANT capacity (ckt style) per sector, more or less independent of
coverage, or even degree of sectorization (not rigorously true, but a fair
approximation in most circumstances). The original Bell Labs notion of
increasing capacity by cell splitting continues to work for SSMA, at least
in the sortof "thermodynamic" sense of mutual interference.

I look forward to the continuation of this debate ... Maybe even to a
conclusion or two!

   -- Arthur

---

From: Amanda Walker <[email-masked]>
Date: Mon, 1 May 2000 11:47:57 -0400

[This is a small diversion from the technical aspects of Mobile-IP, but it
seems relevant.]

First off, I should note that as an engineer I think of PPP over Ethernet,
wireless, DSL, etc. as a kludge, at least from a purely technical
standpoint.  However, there are more than just technical factors at work.
PPP is popular for a variety of reasons, but the major reason it is being
deployed over wireless, DSL, and other media is that it makes access look
like a phone call.  Existing systems (billing, support, usage monitoring,
etc.) know how to deal with phone calls, and existing operators will always
ask vendors for new products by framing their requests in terms of what they
already have rather than the problem they are trying to solve.  This is
unavoidable, I think, and it's a particular challenge for vendors.  The same
effect also applies to end users, although the individual amounts of money
are a lot smaller :-).

When an operator asks for "faster wireless data calls", an ISP asks for a
"wireless dialup POP", or a telco asks for a "layer 2 gateway", it can be
very difficult not to sell them what they are asking for.  This is how, as
an industry, we've ended up with PPP over Ethernet for DSL, huge L2TP
networks for access wholesaling, and so on, with analogous wireless products
recently making their debut from several big vendors (and more in the
pipeline).  From a technical standpoint, these are kludges if you view the
problem as providing ubquitous IP with the lowest possible overhead.  If the
only challenges were technical, none of this would be around.  However, PPP
and L2TP work (for various values of "work"), today, with off the shelf
hardware and software.

This is particularly true for the unlicensed/low-power arena, since for all
that cellular providers often disregard technology like IEEE 802.11b because
it's unlicensed and low range, those very facts are strengths as well.  A
budding provider can deploy a wireless access infastructure serving tens of
thousands of simultaneous users with 100x the on-air data rate of cellular
data without any licenses, approvals, or whatever--just money and the rights
to stick little grey boxes every few hundred feet.  And they can do it
today--with shipping, field-proven products.  Airports, hotels, high-rises,
convention centers, ... backhaul it with DSL and you can even use the
existing wireplant.  Very lower barriers to entry, very fast product cycles,
more efficient reuse of spectrum, and lots of leverage from existing
products and infastructure, particularly the billing and provisioning
infastructure [disclaimer: we make all of these products, so I am probably a
bit biased :-), though you can also do it with products from most of the
other big vendors at this point, now that router vendors are buying up WLAN
vendors...].

It'll happen, and it may well be speaking PPP & L2TP if nothing better (from
a business case point of view) comes by--people will build their networks
with whatever technology is ready and solves their business needs.  And
this, I think, is the biggest danger in thinking of Mobile-IP as a
"cellular" technology, with 5-7 year product cycles, slow adoption of new
technology (often with good reason, to be sure--essential services have
different operating constraints than discretionary ones), and high barriers
to entry.  The ISP/datacom market is a very different place than the telco
market.

Amanda Walker <[email-masked]>
Lucent Technologies InterNetworking Systems