Thursday, June 14, 2012

Is evaluating every device on your WLAN necessary? Yes!

I was recently tasked with assisting in the wireless configuration of an evaluation/demo unit that was going to be on-site for a few days. The device was a portable x-ray machine with a remote plate that communicates with the portable unit.

After assisting with the configuration of the portable unit, I inquired as to how the remote plate communicates with the portable. I was told it had an 802.11n bridge built in and that is how it communicated. Since I could not access the configuration of the portable or the plate, I used my protocol and spectrum analyzer to see how it was communicating.

As soon as the main unit was turned on, I noticed an access point on channel five.  The technicians ran a test of the portable x-ray and the remote plate for me and this is what I saw when the unit took the picture and transferred it over the “bridge link”.





As the saying goes, the packets never lie. Here are a few screen captures from my protocol analyzer.







From all the evidence here, knowing those packets never lie, is this configuration really a bridge?  I discovered that it is not a bridge - it is really an access point and the panel is a client.

Is the channel set up properly? No. It is set to channel 5, which is not a best practice in the 2.4 GHz range.

What is your opinion of the Channel Bonding?   I do not believe in channel bonding in the 2.4 GHz range.

Would you allow this device in your environment?

For those of you like me who always want to know what’s under the hood – here’s what I found:


1 comment:

  1. Seems like Portable X ray unit is set up on channel 5 in the 2.4 band. In the US at least it is recommended that channels 1, 6 and 11 be used in the 2.4 band to avoid interference. I see APs on channels 1, 5, 6, 10 and 11. So devices are not set on the right channel.

    On the channel bonding issue, it is also recommended that 40 MHz channel be used in the 5 GHz band as there's lot more room in this band to avoid interference.

    From the screen shots, I'm not able to determine if this configuration is a bridge or not.

    Devices need to be configured properly so that they don't cause interference. Whether this device should be allowed in the environment depends on specific corporate policies.

    Karthik Krishnaswamy
    Product Manager at AirMagnet.

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