On Mon, Jul 22, 2002 at 09:26:24PM -0500, Austad, Jay wrote:

> As far as roaming goes, using public IP's isn't going to change the
> functionality of that at all.  Your border router routes for your public
> address range, and your routers on the inside handle the individual routes
> for each ip and tell the border router(s) how to get there.  This can get
> messy though depending on how many subscribers you have and what routing
> protocol you use.  You don't want to be flooding LSA's all over the network
> everytime someone connects, disconnects, or switches to a new access point.
> I think Richochet handled this by making all of their access points connect
> to a central bridge so it was all one big broadcast domain.  That way, they
> didn't have to handle route propagation everytime someone switched to a
> different AP.  

I can speak from personal experience here, very large broadcast domains
like this do /not/ work well, our best bet would be sectors, roaming between
those sectors would require either release/renew, MASQ/NAT, or mobile IP type

> Plus, how viable is roaming with 802.11 or Canopy?  GSM 1800/1900 has
> special provisions for handling frequency shifts due to the doppler effect,
> since many people talk on their phones while driving.  Has the 802.11 spec
> or Canopy been developed with mobile (as in driving) users in consideration?
> While GSM has standard provisions for this, you will lose your signal when
> the distance between you and a repeater is changing faster than 280km/hr.
> While no one normally drives that fast, if wireless data protocols were not
> designed with this in mind the speed at which you will lose your signal may
> be considerably less.  Roaming is a nice to have, but for the most part it's
> probably not going to be a reality because you would literally have to
> blanket the city with access points, the cost would be astronomical.  Just
> look at Ricochet, they did it, but then went bankrupt in the process.  A lot
> of that was their marketing department's fault, but their mistakes make a
> nice lesson for others.

In a flat, moderately 'green' area, I was able to drive from Mankato 
to Wilmar without losing connectivity except in a few dead spots. 
60-70mph doesn't seem to cause any problems, of course, when you're going 
that fast, you shouldn't be playing with your wireless devices anyway =)

The area in question had access points on water towers, grain elevators and
various other 150-250 foot structures with an 8db omnidirecitonal antenna
and directional antennas pointing at weak spots, or up/down a highway.

Overall it works well, if you don't spend $1200 for breezecom radios that
don't even support WEP. A little bit of frequency coordination, and a little
clue go a long way.

> Jay

Matthew S. Hallacy                            FUBAR, LART, BOFH Certified
http://www.poptix.net                           GPG public key 0x01938203