Subject: [MOBILE-IP] WLAN vs. CellularIP

From: Guilhem Ensuque <[email-masked]>
Date: Thu, 6 Apr 2000 11:34:04 +0200

> [Andrew Campbell]
> Since we don't have the protocol spec for
> WLANs or any source code it is difficult to compare them
> with CIP but the question you ask in this context is
> interesting.

How about IAPP ?

Maybe someone from Lucent who is on this list can clarify the status of the
spec as a couple of years ago it was hailed as THE interoperability solution
for WLAN roaming.

the I-D was:
H. Moelard (Lucent), M. Trompower (Aironet), “Inter Access Point Protocol
Wireless Networking Distribution System Communication”, Work in Progress
(draft-trompower-iapp-00), March 1998

but it has expired long ago, and the only thing I heard was that the
concerned technical teams at WLAN vendors were too busy implementing to
bother formalising the standard any further. Anyhow, the idea is
interesting:
The approach is a hybrid L2-L3 scheme:
It uses an IP-level 'signalling' protocol for handover and distribution of
topology information.
However the 'handover' is achieved through addition/deletion of L2
forwarding entries in the access points ('intelligent' MAC bridging).

Hope this helps

Guilhem Ensuque          | [email-masked]
                         | +33 6 15 74 53 90
Northstream AB           |
Sophia-Antipolis, France | www.northstream.se

---

From: Amanda Walker <[email-masked]>
Date: Tue, 11 Apr 2000 12:50:22 -0400

Sorry for the delay in responding.

Pomwenger Werner wrote:
> When I'm going to use MobileIP for macro-mobility and my foreign
> network consists of one subnet with several WLAN access points,
> isn't it possible to roam between the access points seamlessly, without
> a new registration at the home agent ?

Yes.

> What is the disadvantage
> of using WLAN for micro-mobility (roaming within one subnet) ?

In practice, very little.  If you're roaming between access points within a
single subnet, existing WLAN technology works pretty well; this was the
problem it was designed to solve.

> Maybe anyone has a paper with a comparison of cellular ip and wireless
> LAN. I didn't find anything. It would be of great help to me.

Cellular IP and WLAN work at different layers and on different scales, as a
couple people have already described.  WLANs make a wireless coverage area
look like a traditional LAN as much as possible, working at the MAC layer.
Current WLAN access points are basically smart MAC-layer bridges.  Cellular
IP works at the IP layer.  They solve different problems, although CIP could
conceivably take over the functions of roaming between access points as
well--it seems pretty scalable.

Andrew Campbell wrote:
> It is natural to think about 'WLAN vs. Cellular IP'
> if you consider that Cellular IP is solely operating at the
> data link in a wireless LAN subnet setting
> or in larger bridged WLANs. Some very large scale
> networks have been build (at CMU) using Lucent's WaveLAN in this
> context but I not sure bridging is an infinitely
> scalable solution. Others may be more informed.

Bridging is not infinitely scalable, for all sorts of reasons.  It's
actually not too bad for pooling a set of access points into a single
coverage area, which can then be assigned a single IP subnet that can be
treated like a LAN subnet for administrative purposes.  For things like
campus networks, this can work very well if a little care is taken in
designing the network.  This is how WaveLAN has been generally used so far,
for example.

> with CIP but the question you ask in this context is

The standardization of IEEE 802.11, and the publication of IAPP (even though
the draft expired without further action) has helped a lot in this regard, I
think.  Certainly more information is available than there used to be,
although it's also true that most of the wireless vendors have not fully
shifted from a proprietary mindset to an open-spec mindset.  It's happening,
but more slowly than some of us would prefer, even internally...

> [List of CIP achievements omitted for brevity]
CIP is indeed very cool stuff.

Guilhem Ensuque wrote:
> Maybe someone from Lucent who is on this list can clarify the
> status of the spec as a couple of years ago it was hailed as THE
> interoperability solution for WLAN roaming.

Generally speaking, the WLAN standards, including IAPP, are aimed at use
within a single administrative doman.  As such, they are quite useful for
supporting micromobility in single-provider networks (campus networks,
corporate wireless infastructures, etc.), but they are not likely to scale
well for multi-provider networks.  You could use IAPP to provide handoff
between administrative domains, but at least at first glance it would be
pretty annoying to do so.

> bother formalising the standard any further.

This is correct to the best of my knowledge.  IAPP is deployed and working
now, but I don't know what the status of the standardization effort is at
this point.

Amanda Walker <[email-masked]>
Sr. Software Engineer
Lucent Technologies, Inc. InterNetworking Systems