Max number of users per AP ?

28 Mar 2005 7:20 PM

Paul

Just curious what the practical limit of number of users per access point
is?

I ask because we use the Proxim AP-2500 and in real world situation strange
things start to happen at about 80 simultaneous wireless laptop users.
We'll see existing users get kicked in favor of new users. Their spec sheet
states it will support 250 users per radio, and two radios can be installed.
I have a hard time beleiving that 500 users could all be talking to the same
AP at the same time? Can that many machines talk on the same 802.11b
channel at the same time?

-- Paul

28 Mar 2005 8:00 PM

Jeff Liebermann

On Mon, 28 Mar 2005 14:20:50 -0500, "Paul"
<paule-nospam@mindspring.com> wrote:

>Just curious what the practical limit of number of users per access point
>is?

The limit for DHCP assigned IP's with Class C subnet mask is 253.

The rule of thumb is:
100 average web and email users.
10 average business users.
1 peer-to-peer or Bitorrent user.

>I ask because we use the Proxim AP-2500 and in real world situation strange
>things start to happen at about 80 simultaneous wireless laptop users.
>
>We'll see existing users get kicked in favor of new users.

You can use an SNMP MIB browser to look at the number of MAC addresses
you have in the table. Syslog output should also give you a clue as
to what's happening. If the MAC addresses look weird, you might
search Google for "MAC flooding".

Also, users getting "kicked off" (a very vague term) can be caused by
running out of DHCP IP address leases as new MAC addresses appear.
Check your DHCP server for sufficient IP addresses and make sure that
the lease time is fairly short (i.e. 30 mins) if you're running a
system with lots of transient users (hot spot, coffee shop, hotel,
etc).

>Their spec sheet
>states it will support 250 users per radio, and two radios can be installed.
>I have a hard time beleiving that 500 users could all be talking to the same
>AP at the same time? Can that many machines talk on the same 802.11b
>channel at the same time?

Drivel: 50 users per radio for 802.11a.

I don't have a number. I know of several low bandwidth WISP systems
with more than 100 active users on a single radio. I've also done it
with tests in the lab (using a different access point). The available
bandwidth divides nicely between the 100 users. However, I've never
tested the AP-2500 for capacity.

--
Jeff Liebermann    je***@comix.santa-cruz.ca.us
150 Felker St #D   http://www.LearnByDestroying.com
Santa Cruz CA 95060    AE6KS 831-336-2558

29 Mar 2005 4:21 PM

Paul

> Drivel: 50 users per radio for 802.11a.

Proxim tech support does say in fact only 50 users for 802.11a, but 250 for
802.11b.

I will try shortening the DHCP lease time to 15 minutes, that may very well
be the root of my problem.

-- Paul