[ previous ] [ next ] [ threads ]
 From:  "Lee Sharp" <leesharp at hal dash pc dot org>
 To:  <m0n0wall at lists dot m0n0 dot ch>
 Subject:  Re: [m0n0wall] multiple access points with single m0n0wall router]
 Date:  Sun, 28 Jan 2007 14:20:34 -0600
From: "Mike" <lists at southwestech dot com>
> Mats Lundqvist wrote:

>> WDS is a bad idea for anything more then two APs. Sure, you get basic
>> roaming functionality and eliminate the usual problems with repeaters,
>> but performance goes down the drain.

> And for straight internet access, how much throughput does one actually 
> need? 2Mbps/512Kbps or so? I run several hotels in the city with at least 
> 4. No bandwidth issues with net access. No networking between systems is 
> needed.

You would be surprised how quickly 2 meg traffic can bring down an AP.  Not 
to mention all of the pipes in the primary.  This ends up killing latency 
fast.  You are also assuming that the bandwidth you are halving is 54meg. 
Often it can drop down to 11 meg, so once it makes 2 hops you are at 2 or 
so...  And as it gets congested it also has to handle the collisions and 
retransmits, so effective bandwidth can drop to 1 meg.

>> With WDS, throughput get cut in half with every node you add (rough 
>> estimate).

> A very close rough estimate. I would never run WDS if networking was a 
> factor, IE: a business environment sharing files etc. but to me, I don't 
> *think* that is what the original poster was looking at...

And no one is on the internet doing business and sharing files? :-)

>> And with WDS, you still de-associate from the old ap and re-associate
>> with the new ap, so it's not really _true_ roaming anyway...

> True enough, but the new AP is an extension of the old AP. Dedicated AP's 
> running on the same channel will conflict with each other, no? That is 
> what I have found at least.

Everyone is right here.  Swapping APs is the same in WDS or with a bunch on 
a wire.  And sharing one channels will make for bizarre drops and 

>> If you have the option [of using cables to the aps], always go with
>> stand-alone APs instead of WDS. Use the same channel and the same
>> SSID, preferably with little overlapping coverage areas (so clients
>> can roam, too much overlap= performance goes down) and you get the
>> same functionality as with WDS with no performance loss.

> The reason WAP's were looked at for all the locations (hotels, 
> restaraunts, etc.) was because cables were not an option.  Performance 
> loss was not an issue as it is merely for net access, no networking 
> involved.

Tell that to the guy who calls with "interweb problems."  Poor performance 
means customer complaints, and difficulty troubleshooting.  Wireless does 
not mean poor performance.  Poor design means poor performance.

>> But if you don't have a choice (cabling too expensive, not feasible,
>> on a budget etc etc..), WDS is a good option.

> A guess for a little more background, when we initially tried several 
> dedicated AP's in these businesses, we found that there was a lot of 
> fighting with AP superiority so to speak. Clients in certain areas of the 
> building were finding that their laptops were jumping from node to node 
> depending on the signal, and were losing connectivity. IP stayed the same, 
> but the channel changed. When we set the AP's to the same channel, it got 
> worse as the AP's began fighting with one another. The companies (on their 
> own- without consulting me) then bought a bunch of repeaters for us to try 
> on the recommendation of one of the employees, and we began receiving the 
> same issues, only compounded with the issue of the repeaters producing IP 
> address conflicts (a linksys special ;-)) to the clients on the system.

That node jumping is the fault of the XP brain dead client.  More trouble 
for me... (cursing deleted)  Anyway, in some locations we use different 
SSIDs.  (Hotspot, HotSpot, Hot Spot, ...)  This way no one jumps AP, and 
with a quick look at status we know what AP they are having trouble with. 
If you put all SSIDs in the "preferred networks" it will still roam, but 
only when a connection drops.  Wireless range extenders are the spawn of the 
devil.  They never work right.

> After this, I explored WDS as an option, and I have not heard one 
> complaint. I have kept in touch with the businesses, and they have told me 
> the system has not given them one problem, and they are extremely happy 
> with the setup.

WDS can work well.  It has issues, but can be a solution.  However, when 
something does go wrong, it can be harder to troubleshoot.

> I don't really disagree with what you have said, I just think that 
> depending on the requirements, certain configurations are better than 
> others. For the requirements these businesses had of me, WDS was the best 
> option, simply because they have no more complaints, and I don't get 5 
> phone calls a day. Many will disagree I am sure, but for a budget minded 
> hotspot, this is working wonderful.

Right tool for the job.  I only want religious conviction from a priest, not 
my network guy. :-)  Some other things to consider is client mode bridging, 
point to point bridging and point to multipoint bridging.  I do a lot of 
this.  However, my "bridge network" is different from the public AP network, 
and SSIDs are not broadcast.  This gives full bandwidth to the bridging 
network, and the APs act as wired APs.  Most often I use Linksys WRT54GLs 
with Thybor firmware.  Solid and fantastic troubleshooting.