Access Points

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Frequent Contributor I
Posts: 63
Registered: ‎11-10-2009

Eliminating slow clients using SSID profile?

Hello,

We have a location where an access point has been installed as a 'hot spot' (i.e. the building is not flooded with wireless but it's limited to a few common areas). In this building, users are reporting slow performance.

Looking at the distribution of packet rates (Monitoring -> Access Points -> -> Channel ), we can see a significant (around 50%) proportion of the packets are at 1-2Mbit/s.

As the AP is really only intended for use in a specific location (a single room), we think these slow clients are probably using the AP from adjacent rooms (we haven't gone out to try and locate them -- actually, how do we tell what rate a particular client is using at the moment?).

Can we adjust the ssid-profile to not allow lower rates? Certainly we've tried building one with:

g-basic-rates 6 9 11
g-tx-rates 6 9 11 12 18 24 36 48 54

... in a hope to eliminate things at 1-5Mbit/s.

Is this a valid thing to do? If so, is there any guidance available on what numbers we might put in to eliminate the slow clients.


In terms of monitoring, can we check what rate a particular client is associated at?

Also, we can't find a way to reset the accumulating totals on the pie chart and statistics on the above web page -- is there a command to do this?

Thanks,

- Bob
Guru Elite
Posts: 20,553
Registered: ‎03-29-2007

Slow users

There are a number of things that can be causing slow user traffic:

- Congestion
- Interference

If you have ArubaOS 3.3.2.8 and above, you can use the "drop broadcasts" parameter to decrease congestion and the broadcasts that rob you of bandwidth due to broadcast traffic. If you have dual-band access points, you can also enable band steering to move the users that can do 802.11a to that less-congested band, leaving only those users that MUST do b/g on the 2.4ghz band.

Limiting the lower rates sometimes works, and a few clients don't like it. If you are going to limit rates, why don't you go all the way and only allow 9 and above. If things do not improve, ensure that you don't microwaves, baby monitors, 2.4ghz phones, bluetooth devices, wireless video, etc in the area, because those are the usual suspects that cause degradation and connectivity issues.


Colin Joseph
Aruba Customer Engineering

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Frequent Contributor I
Posts: 63
Registered: ‎11-10-2009

Re: Eliminating slow clients using SSID profile?

Hi,

We've been out and done an air survey but haven't found anything particular interfering -- there are a LOT of other APs which can be detected but they've all got a very low signal, so we don't think it is those.

There may be something local causing problems (it's in a science department, so there might be some piece of equipment, or even a microwave in the kitchen!) but we've not found evidence of that. When we've been out to test, it all works fine, so we're having trouble getting a handle on when and why the problem occurs -- if it's just load on the access point(s) or something else.

We have band steering enabled; we're not running 3.3.whatever yet but will be upgrading soon and we can look at the feature you mention. Presumably that just drops broadcasts over a certain threshold (an egress version of something like Cisco's 'storm-control broadcast level ...'?) and, as long as it's tuned correctly, might stop something misbehaving from causing trouble?

Certainly we can change the rates we accept but I was mainly concerned about dropping 1-2Mbit/s as that was accounting for 50% of the packet count, so I assume a very large %age of air time (can I view this?).

Any further suggestions welcome!
Guru Elite
Posts: 20,553
Registered: ‎03-29-2007

Re: Eliminating slow clients using SSID profile?

If you have 3.3.2.9 and above, you should be able to drop all downstream broadcasts at the AP level. If you are using band steering, you probably have drop broadcasts, as well. it is located on the Virtual AP. dropping broadcasts can make a huge difference. Manipulating the rates, less of an impact. Clients that are only associated and APs that beacon always send their traffic at the lowest rates, that could mean half of your traffic is management, which is sort of high, but is not the end of the world. Get rid of your broadcasts, first.


Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Frequent Contributor I
Posts: 63
Registered: ‎11-10-2009

Re: Eliminating slow clients using SSID profile?

I've got my version numbers wrong -- we are running 3.3.something, so I've enabled the broadcast-filters for all VAPs on the affected APs:

# broadcast-filter arp
# broadcast-filter all

I've also fiddled with the base and tx rates to remove anything below 6Mbit/s. On an access point here, my client associates fine and I'm getting 2Mbyte/s from an 802.11g client, so that seems OK.

I'll check back with the affected users.

Any further tips would be welcome -- it would be nice to find a way to find the association rates of clients.

I have, however, found that doing Access Points -> (select one) -> Channel and changing 'Data Type' at the top to 'Rate' and not 'Total' gives me the measure for the last refresh period, so lets me view what's going on right now more easily.
Guru Elite
Posts: 20,553
Registered: ‎03-29-2007

Association Rates

Bob,

You can get the association rates of clients by doing a "show ap association ap-name

Remember that those rates can change fairly quickly, but the output of the command above can be delayed as much as one minute sometimes. Clients, when doing nothing will always associate at the lowest supported rates, to communicate management frames. That does not automatically ensure slowdowns. There are things like congestion, that play a greater role. if you do a "show user mac " there is a retries parameter which should stay below 20% sustained. Anything more than that suggests congestion and is more indicative of the performance of a client.


Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

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