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WLPC 2024 PHX Day 1

Today I was lucky to be able to present in front of WLPC about Telemetry, and attend a discussion about 6GHz client behavior as well.

Presentation

I think my presentation was pretty well recieved. I was slightly worried for a second when my USB-c dongle failed to work, but fortunately they were able to let me borrow one of theirs at the last minute.

I think the only thing that I forgot to mention was that we use timescaledb to continuously aggretate the data over time so that we have as much data as possible about as much time as possible not just as much data about recent history as possible, but I don't think that anyone noticed. Other than that it went great!

Deep Dive: 6 GHz Client Behavior

  • Clients can not speak directly to each other. I think that's kind of unfortunate personally because I think client-to-client direct communication is kind of a cool feature of 802.11 networking but I figure that they have their reasons.

  • Preferred Scanning Channels are a subset of channels that are recommended for clients to scan. I think apple devices may only scan these channels which can be a big issue for network discovery particularly if SSID is only on 20 MHz.

  • There is a way to calculate frequency from channel number and vice versa, at least for 2.4 and 5 GHZ channels. If you want to calculate the center frequency of a 5ghz channel, multiply the channel number by 5 then add 5000 to the result. If you want to calculate the center frequency of a 2.4 GHz channel, reduce the number by 1, then multiply the result by 5 and add 2412 to the result.

  • FCC asks to prioritize using higher frequency 6 GHz channels above using lower frequency 6 GHz channels.

  • Reduced Neighbor Reports (RNRs) inform clients about other ways to join the netork. I learned of these while studying for the CWAP but it was good to have a refresher. Basically a non-6GHz client reads this information in the beacon, and the information includes details that the client can use to connect to another BSS. This includes BSSID to connect to, and channel to find it on.

  • Unsolicited Probe Responses (UPRs). Another thing that I should know about already from the CWAP, these are like mini beacons that are sent out more frequently than regular beacons (roughly 5-10X as often I think). These help clients know what BSSes are on a channel without needed to dwell a full beacon interval.

  • There is an awesome Wireshark Profile for 802.11 debugging that is maintained by WLAN Pros!. You can install it by right clicking on Profile in the bottom right and choosing import.