Dot11 Guru

802.11, Troubleshooting

A-MSDU frames crashing wireless barcode printers

Frame aggregation is usually a godsend in wireless networks. It helps to reduce excessive overhead required when sending single frames to the same destination.

However recently I encountered a very strange issue during a wireless refresh in a large warehouse.

Wireless printers were non responsive and after a period of time were timing out and not connecting back to the network.

After performing a packet capture, it was noticed that the printer would stop responding after it receives a single A-MSDU frame, from here the re-transmissions begin. This happened on a number of occasions.

Eventually 802.11n was disabled as an attempt to prove the devices was crashing on receiving A-MSDU frames. The printer began working as expected. This was the first time i’ve come across an issue like this. Needless to say, there’s a support case opened with the specific printer vendor to get this checked ASAP.

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