Prism AP's

[bobbyc]

I know you starOS people don't use anything but hermes/ruby in your APs; but with your limited use of prism AP's, I was wondering if you've come to the same conclusion as I have; regardless of prism 2.5 card (smc, senao, bromax, etc), clients have a hard time (comared to hermes AP) staying associated at 11mbps. Take this for example; I had a hermes AP with a couple stock WET11s set to auto, and a few orinoco USB clients associated to it. They would always be at 5.5 or 11mbps... even one of the USB clients that had a -80 signal.
I swapped out that hermes AP for a senao 200mw card; and now they all have excellent signals (the -80 customer is now at -73) but their rates are all over the place... which is in turn messing up pings and thoughput for all associated clients.
Is there any code you guys can add to the prism AP drivers that 'encourage' the clients to stay at 11mbps more often? Or is it just a limitation of using prism as AP? I've seen this problem in on many different hilltops where I've tested these prism cards (swapped out hermes APs) All my hermes clients are fw 8.72 and all my WET11s are either hermes or prism 2.5 1.1.1/1.5.6
Thanks!
Bob C

[bobbyc]

bump...
I'm going to setup a freebsd hostap temp machine for the hilltop to determine if this is a AP driver problem or a client driver problem...
Bob C

[tony]

If your clients's rates are floating around, yet have a good signal (-65 or better), you can lock the AP to 11Mbps. The rates you see on the association list are what the client is transmitting at, so the client needs to be locked to 11Mbps as well.

[bobbyc]

That's what we get for using usb clients that don't have locking ability (agere). The problem we're seeing is that when a usb client that decides to be at 1mbps is uploading, that messes up the entire system for our other clients on that AP.
Does Valemount have usb clients installed? Have you seen the same thing happen?
We might have to swap out all our usb clients for ethernet clients that can lock at 11.
Bob C

[tony]

Unfortunately we use DWL-520 or PCMCIA ORiNOCO devices for out client installs which have the ability lock the rates.

[bobbyc]

So you use pcmcia orinoco cards in starOS machines? Because the windows clients don't have the ability to lock rates, right?
Bob C

[tony]

I believe our installers found a way to lock the rate via a registry key, or the device's advanced properties. I don't know the details however.

[georgew]

I have a couple of StarOS boxes talking to each other across a street. They have good signals, and both sides are locked at 11mbits.

So when I see it bobbing between 2 and 11 megabits, I assume this is normal behavior... perhaps essid's are transmitted at 2mbits or something.... Or am I seeing a problem with my prism2.5 card in my access point?

[tony]

All beacons and multicast packets are transmitted at 2Mbps as to be 'legacy' compatible, so the client side may show 2Mbps once in a while when there is a low amount of traffic going through the link.

Thanks!

[bobbyc]

Hi Tony,
If so that would be great. I really need to find out how to do this and if it can be done with usb clients. In your free time could you look into this and shoot me an email offlist or share it here? Otherwise we need to get started swapping out usb clients for ethernet clients. I've personally logged into some of our APs and seen someone uploading at 11mbps, while another is uploading at 1 or 2 mbps and all clients have massive packet loss.
Thanks so much if you can help,
Bob C

[bobbyc]

Just thought I'd add:
This winter/spring we updated all our clients to 8.72 fw, which enabled them to associate to the AP at 11mbps the majority of the time... but all it takes is 1 client to associate at 1mbps and upload something to mess up the entire AP. If we knew that when we started this venture I'm sure we would have never deployed usb clients :)
Bob C

[bobbyc]

I was searching the registry of my XP tech laptop tonight... I have had numerous usb and pcmcia devices on my laptop over time.
I found a txratecontrol that is set to 3 by default.
Unfortunately this only came up only under my orinoco pcmcia devices and buffalo usb devices. It did not come up under my orinoco, avaya, agere usb devices.
Is this a line that can be added to the registry of the orinoco/avaya/agere usb devices? Or is this the reason you don't use usb clients on your installs?
Thanks,
Bob C

[tony]

This is what the number represents:
1 = 1Mbit Fixed
2 = 2Mbit Fixed
3 = 11Mbit Auto
4 = 5.5Mbit Fixed
5 = 11Mbit Fixed
6 = 2Mbit Auto
7 = 5.5Mbit Auto

You should be able to put the same registry key on devices that do not already have it set. '3' is the default if the key is not set.

I was searching the registry of my XP tech laptop tonight... I have had numerous usb and pcmcia devices on my laptop over time.
I found a txratecontrol that is set to 3 by default.
Unfortunately this only came up only under my orinoco pcmcia devices and buffalo usb devices. It did not come up under my orinoco, avaya, agere usb devices.
Is this a line that can be added to the registry of the orinoco/avaya/agere usb devices? Or is this the reason you don't use usb clients on your installs?
Thanks,
Bob C

[bobbyc]

Sweet Tony, thanks I'll give it a try as soon as my girlfriend falls asleep... where's the nyquil?
Bob C

[bobbyc]

Tony, you are the man! I just switched my orinoco USB to all kinds of rates via entering the registry string TXRateControl and giving it different values.
I noticed on the Buffalo USB clients there is a RTS setting value of 3000 in the registry. Since buffalo is hermes radio, if the hermes AP RTS is set to a different value will the buffalo usb clients use the AP value or the registry value?
Thanks again! I have to get started scheduling tech calls monday for all our usb clients :(
Bob C

[tony]

Glad things are working. 3000 means RTS is disabled, however if it was set to another number the AP will still override it.

Thanks!

[bobbyc]

OT question:
I see you use DWL-520 on clients as well. Do you set RTS on those devices? Or do you use them on APs that don't require RTS?
Thanks, Bob C

[tony]

They are set via the advanced properties of the card since they do not adopt the settings from the AP like the ORiNOCO.

[rbolduc]

Hello,
in there any harm in locking clients with lower signal at 2mb and having everyone with good signal at 11mb. I figured this would keep the client from reconnecting at 5.5 and 11 then 2 and causing the AP to try to keep this straight or will this in effect cause the same problem.


Reed

[tony]

The only thing to consider about 2Mbit clients is that the Access Point will drop it's overall speed to 2Mbit when the 2Mbit client is transmitting, or receiving data. This means if your client is downloading a large file, all your associated users combined will not be able to exceed 2Mbit total bandwidth as the AP will be effectively a 2Mbit AP, regardless of it's rate settings. The AP will return to normal once the 2Mbit clients are idle.

Thanks!

[bobbyc]

Tony,
Are you referring to the 2Mbit cards? Because if you have a 11Mbit client card locked to tx at 2Mbit, it will still rx at 11Mbit from the AP that is locked to tx at 11Mbit.. right?

So, if the above is correct, then my response to rbolduc would be that locking clients at 2 and 11Mbit would be bad because if client a is uploading something at 11Mbit while client b is uploading at 2Mbit, then the AP has to switch back and forth and what you get is severe packetloss for everyone on the AP.
Bob C

[georgew]

Keep in mind that there is a time element to the overall bandwidth available. The more time someone is sending at 2mbit, the less 11mbit time there is to dole out. So for example if a 2mbit user starts an upload, and you have his bandwidth throttled to 512kbits, he will use up 50% of your total available airtime. Two users could wipe you out.
On the other hand, a 11mbuit user with a 512kbits bw limit will only use 10% of the available airtime. So if you have people locked in at 2mbit, you should also throttle them at a much slower speed, so they don't consume all of your airtime.

Another way to look at it is at 2mbit a user uses 5 times as much airtime as a 11mbit user... So adding one 2mbit user is like adding five 11mbit users.

[rbolduc]

Thanks for all the input. What I will do is make signals the best I can and lock them to 11mb. Most of my client are using wet11's with a herms card inside with firmware 1.4.3/1.7.4 but the auto setting just locks at 2 mb. Looking for previous posts I found this is true and locking at the wet11 at 11mb does lock the card at 11mb.


So, if the above is correct, then my response to rbolduc would be that locking clients at 2 and 11Mbit would be bad because if client a is uploading something at 11Mbit while client b is uploading at 2Mbit, then the AP has to switch back and forth and what you get is severe packetloss for everyone on the AP.
Bob C

That is what I was thinking also Bobbyc, it was working fine for now with about 3 customers locked at 2mb and 5 at 11mb but I am still in the post-beta stages now and want every "easy" problem worked out now before we go "live".. Did I just say easy problems? is that an oxymoron? :roll:

Reed

[georgew]

... the AP has to switch back and forth and what you get is severe packetloss for everyone on the AP.


The AP switches modulation speeds constantly, even when locked at 11mbits. That is part of the protocol. It is not the switching speeds that kills things, it is the airtime consumption of the slower radios. If your airtime is 100% consumed, the packets that can't find a timeslot rot of old age and are eventually discarded, causing your packet loss.

The ESSID broadcasts are done at 2mbits. Switching speeds is normal and simply a matter of how the dsp modulates the signal, there is no overhead other than the airtime consumed. It's not like a modem where speed shifts require negotiation.

[bobbyc]

Thanks for all the replies. Things make much more sense now. Our problem is that we offer 1Mbit/sec speeds up/down. Since we have all these usb clients installed that change rates, we have clients up/downloading while associating at 1Mbps. When we get finished adding this registry string we'll see a much more stable system.
Thanks,
Bob C

[georgew]

Yeah, with 1megabit thruput limits, a 1 or 2 megabit radio only connection can use all of your airtime and still not exceed your advertized bandwidth rate. That is essentially the same situation I am in, so slow connect speeds simply are not acceptable.

Pump up the gain where you can, and if that is not good enough, swap out the worst offending radios with something better.

[bobbyc]

Everyone has good signal now. This last winter when things were slow we updated all our hermes clients to fw 8.72 and took care of low signals.
All our ethernet clients are locked to 11Mbps, but our usb clients have no way to lock rates, till now. Now we have to go visit all our usb clients and enter TXRateControl 5 in the registry.
Bob C

[bobbyc]

Just a quick observation Tony/Lonnie:
On my hermes APs, if I lock the rate to 5.5, the hermes clients that are locked at 11 via registry stay at 11.

On my prism 2.5 APs, if I lock the rate to 5.5, the hermes clients that are locked at 11 via registry move to 5.5.

I know the prism 2.5AP/hermes client isn't supposed to do that, but in my case I think it works out pretty good. If I had to lower the rate on my hermes APs, I'd have to go to all the clients cpus on that AP and lower their rate too.
Bob C

[tony]

Yes, this is a small difference between Hermes and Prism APs. The Prism APs broadcast their supported rates to the clients, so if you lock the AP down to a lower speed the clients will not go higher than that rate themselves. While the Hermes APs can be set for a lower TX rate, they do not broadcast this change to the clients so the clients will continue to associate at the higher 11Mbps.

[bobbyc]

right on, thanks. Just wanted to run it by you incase it was a driver mistake. I know you guys don't use prism 2.5 APs much if at all.
Bob C