802.11 Field Notes

Why I stopped calling it 802.11r

Most Wi-Fi engineers call it "802.11r" and move on.The problem: 802.11r is just the amendment number. What actually matters in a roaming failure is whether Fast Transition negotiated correctly — and that lives in three specific frames most people never look at.The MDIE (Mobility Domain IE) tells you if both AP and client agreed to use FT at all. The FTIE carries the PTK keys. If either is missing or mismatched, your client re-authenticates from scratch — adding 500-800ms to every roam — and nobody notices until a VoIP call drops.I've seen this exact failure in enterprise deployments where the controller "showed green" the whole time.What I do now: upload the PCAP to WiFi Analyser and look at the FT Auth frame directly. It either shows algo=2 (Fast BSS Transition) or it doesn't. No guessing.If you want to see what this looks like in a real capture — the tool is free, no install:→ app.wlananalyser.com