Need the clients to roam between APs more quickly

[bpowell]

Hi all,

In warehouse or manufacturing environments where there are a loarge number of clients and a large number of APs (350s in our case), the 350 seems to wait until the quality of its association is really lousy before it tries to roam to another AP. With latency sensitive applications like telnet or 5250, this causes problems with session lockups and excessive battery use on the client because of too many retries.

How can we get these clients to roam more quickly when their sesion _begins_ to degrade?

The old Aironet/Telxon 2.4GHz networks were able to set ELH and other thresholds to cause more proactive roaming.

We have tried limiting cell size by power levels and/or restricting data rates, but it doesn't seem to improve.

Any ideas?

Thanks,

Brent

[ED CARMODY]

Try upgrading to the latest firmware releases for clients & APs.

Are the APs set to emulate a plain-vanilla 802.11b AP? I've seen reduced roaming speeds when having to comply with the standard.

[bpowell]

Thanks for your reply.

Our APs have the latest software and radio firmware package (11.08T). Our clients, are a only couple of versions behind on both radio firmware and WinCE driver.

Thanks,

Brent

[blue.modal]

Retries.

It's a dumb way to solve the problem, but it works.

For proactive roaming set the RTS and CTS reties to a number like 16 (max 128). For tenacious grip use 128.

Make sure to try both the Client and the AP to get the desired result.

Doing something ridiculous (like setting retries to 1) will cause more problems than it solves.

[bpowell]

Thanks for your reply!

I assume that you meant RTS retries and data retries. There is no setting for CTS. Are you reommending a change to the RTS threshold? If so, why?

Thanks again for your help.

Brent

[blue.modal]

You're right, RTS & Data (I'm not looking at a console).

The retries control how many times a client and/or AP will attempt to re-transmit, and therefor how soon it will give up on the AP that it is moving away from.

The sooner it gives up on one, the sooner it will look for another, and when it looks for a new AP it will take the strongest signal.

The inverse is true as well. I've had trouble with clients roaming too quickly in a noisy environment - essentially jumping back and forth between APs so fast that both APs give up on them - where setting the retries higher solved the problem.

[bmcmurdo]

"Max. Data Retries" can be configured under the "AP Radio Hardware Page" and is described here:

http://www.cisco.com/univercd/cc/td/doc/product/wireless/airo_350/accsspts/ap350scg/ap350ch3.htm#65726

The RTS threshold is larger by default than any packets you are likely to see, so unless you have changed the RTS threshold, the "Max RTS Retrys" setting should be irrelevant.