The retransmission trap: RF, driver, or congestion
"High retries. Every engineer's first instinct is RF. They are right about 40% of the time." ·
wlan.fc.retry == 1 is always the first filter I apply. Above 10% something is wrong. The filter confirms the symptom. It tells you nothing about the cause. Treating congestion as RF (adding APs) makes congestion worse. Treating RF as congestion does nothing.
Step 1 — Correlate with RSSI
Retries clustering below -75 dBm = RF problem. Retries at strong signal = driver defect or congestion.
Step 2 — One device or all devices?
Retries from one device while others are clean = device-specific. Driver defect, NIC firmware bug, or aggressive power management. The channel is fine. That device is not.
Step 3 — FCS errors vs ACK loss
FCS errors at strong RSSI = co-channel interference, not coverage. This is the most common misdiagnosis — engineers blame distance when a neighbour AP on the same channel is destroying frames mid-transmission.
Retries from one device at strong RSSI → Driver. Fix: update or replace.
Retries across all devices + high QBSS CU → Congestion/CCI. Fix: channel plan or BSS Color.