I have to agree with all of Jim's points here. In addition to that, you have
to add in the cost for security. You cannot allow your AP to handle more
than 25 clients and do the MAC address filtering. That means that you need a
Radius Server. The WEP Encryption has been broken and is now totally useless
(like I had been saying all along), so you need a VPN, and you need to set
up a DMZ for them which is a firewall, or at least and ACLed router.
There is a lot to consider before leaping into a wireless network.

-----Original Message-----
From: Jon Knight [mailto:J.P.Knightlboro.ac.uk]
Sent: Tuesday, July 17, 2001 4:01 AM
To: Lamont Flowers
Cc: wirelesslists.samba.org
Subject: Re: need an expert wireless network GURU opinion!

On Mon, 16 Jul 2001, Lamont Flowers wrote:
> Hey guys in the future I'm going to be heavily involved in the designing
> phase of
> a wireless network for a school of say with 1000 plus worstations were
> they'll
> upgade to a purely wireless network what are some of the things I should
> consider
> in my approach from hardware usage to breaking the network down to
> specific user
> groups,vlans etc.

This might be an unpopular view on this mailing list (but that's never
stopped me before :-) ) but I'd say think *very* carefully before moving
from a wired network to a completely wireless network. For one thing if
you've got a wired network in place and if it is using structured cabling,
you've got the potential for a much cheaper and higher bandwidth link to
your workstations. Wireless networking is an order of magnitude or two
slower than current commodity Ethernet for example (11Mbps vs 100Mbps. Or
even 1Gbps for server and backbone connections).

On a wireless network, the client machines require a PCMCIA card (and a
PCI/ISA bridge if they are desktop boxes) that costs a lot more per
workstation than a commodity PCI Ethernet card (over here its about 100
quid for a cheapie 802.11b PCMCIA card and about 15 quid for a 10/100 UTP
PCI Ethernet card. PCMCIA Ethernet cards are about 35 quid last time I
checked). They then share the channel to the Access Point with all the
other clients in the same location (so your 11Mbps raw capacity, which has
already dropped to about 7Mbps when you take into account framing, etc, is
then shared amongst all those clients). This means that for 1000 clients
you're likely to need quite a few Access Points (almost certainly multiple
APs in "lab" type environments where you might have 50 or more PCs active
at once). APs aren't cheap: the low end Buffalo APs we've got swing in at
around 200 quid. Normally the APs are dropped off the wired network but
if you're going completely wireless you'll be using up channels for
inter-AP backbone traffic. You'll also need more expensive APs that can
handle two links (one for the client connections and one for the inter-AP
links). Or just forget APs and have PCs with twin wireless cards acting
as routers (running Linux or BSD for example).

Instead of aiming for a purely wireless network, I'd look to target
wireless equipment in locations that can make best use of it: meeting
rooms, lecture theatres, bars/cafes and popular seating/meeting areas.
These are places where there is a constant "thrash" of people (ie the PCs
aren't fixed to the desks!) and where trailing cables can be a
pain/dangerous. Leave the labs and offices wired as the machines in there
don't move about much. Of course you'll need to use common sense as well:
if you've got some little room that you want to put one or two PCs in
which is very difficult to get a wired network link into then a wireless
network link might make more sense.

As for user groups and VLANs that's a decision for you as the network
manager to take. Only you know what the situation on the ground is: are
there well defined groups of users already, do you have departments which
might have little offshoots pop up all over the place, etc, etc.

Tatty bye,

Jim'll

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