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What the sensor can tell

The sensor hears the client's surroundings from next to the client. That decides what it can judge and what it cannot.

What it sees well

  • Events: association, the login (the 4-way handshake, SAE, EAP), disconnects, roams, channel switches. A failed login or a refused association is read frame by frame, with the side that stopped.
  • Block Acks: each side acknowledges the other's frames in a bitmap, at a low rate that the sensor decodes reliably. The client's Block Acks tell how the AP's frames fared, the AP's how the client's fared: a delivery rate per direction, as the receiver reports it. It is the primary measure; the retry bit is secondary, since a frame the sensor missed followed by its retry looks like a retry alone.
  • The AP's signal at the client: the sensor next to the client hears the AP about as the client does.
  • The channel: the other APs on it and the load the AP reports in its beacons.

What it cannot see

  • Encrypted management. With PMF (always with WPA3, 6 GHz and Wi-Fi 7) the reason of a disconnect, BSS transition requests and neighbor reports are encrypted. The sensor sees that such a frame went and how long it is, and knows an SA Query and a Block Ack setup by their size; Mist has the reason of a disconnect, not what a BSS transition request or a neighbor report said.
  • The uplink's scheduled frames. Under uplink OFDMA the clients send in sub-channels the sensor cannot decode; their acknowledgement, which it can, is what it counts.
  • Every data frame. The sensor decodes data only up to the rate its own signal allows, and the AP beamforms towards the client, not towards the sensor. The share it decodes is shown as capture quality, not as loss; below half, the retry bit and the rate are left out of the rules.
  • The AP's surroundings. Interference near the AP shows only as uplink loss; whether the AP hears noise comes from Mist, where available.
  • 320 MHz. No USB adapter receives it. Channels up to 160 MHz are captured whole.
  • The client's signal as the AP hears it. The sensor is in the client's near field: the client's signal at the sensor says nothing about how the AP hears it. Mist does.

Comparing to take a side

A loss alone takes no side. The rules give it one by comparison: the other direction getting through, a reference client of your own on the same AP doing fine, or Mist seeing interference at the AP. Without such a comparison the loss is an observation, and the verdict stays undecided.

The feasibility analysis goes through each problem class: what the sensor detects, what it attributes, and what limits it.