| Solution |
How AP Handoff Works:
- Client-AP Association.
- A client connects to FortiAP through normal association process, get a radio assigned and starts sending traffic.
- Monitoring Signal Strength and Load.
- FortiAP continuously monitors RSSI and SNR of connected clients. If the signal strength drops below a configured threshold or a better AP is available nearby, the AP determines if a handoff is required.
- Triggering the Handoff.
- The AP decides whether to trigger a handoff based on:
- Nearby APs in the same SSID.
- Their signal strength relative to the client.
- The number of clients already connected (load balancing considerations).
- If another AP offers a better signal, then the client is forced to roam to it.
- Forcing the Client to Disconnect.
- The current AP sends a Disassociation or Deauthentication frame to the client.
- This forces the client to search for a new AP.
- If 802.11k/v/r roaming enhancements are enabled, the transition is smoother.
- Client Reassociation to a New AP. The client device scans for a better AP and connects to it.
- If fast roaming (802.11r) is enabled, the client can transition with minimal latency.
AP Handoff should be enabled in the following scenarios:
- High-Density Environments (e.g., stadiums, auditoriums, office buildings) to ensure optimal load balancing.
- Enterprise Networks where seamless roaming is required to maintain application performance.
- Retail, Warehouses, and Healthcare Facilities where mobile devices, barcode scanners, or VoIP phones require stable connectivity.
- Campus Networks where users frequently move between buildings and need smooth transitions between AP's.
However, enabling AP Handoff without proper tuning may result in unwanted disconnections. A poorly configured network can cause excessive handoffs, leading to degraded user experience instead of improving it.
Things to consider while setting the thresholds.
- Sticky Clients: Some client devices may resist roaming and reconnect to the same AP even after disassociation.
- Frequent Disconnections: If AP handoff thresholds are too aggressive, users may experience frequent drops.
- Roaming Delays: Some older devices do not support fast roaming features like 802.11k/v/r, leading to slower re-connections.
WiFi Event Log Examples:
Below are sample logs that indicate an AP handoff event:
date=2025-02-27 time=14:35:21 id=7372210272947143044 logid=0104043657 type="event" subtype="wireless" level="notice" action="client-disassociated" msg="Client ab:cd:ef:gh:12:34 was disassociated due to AP handoff" logdesc="Wireless station disassociation" ssid="Corporate-WiFi" ap="AP-1" reason="AP handoff triggered" stamac="ab:cd:ef:gh:12:34"
date=2025-02-27 time=14:35:23 id=7372210272947143045 logid=0104043595 type="event" subtype="wireless" level="notice" action="client-associated" msg="Client ab:cd:ef:gh:12:34 successfully associated with AP-2 after handoff" logdesc="Wireless station association" ssid="Corporate-WiFi" ap="AP-2" stamac="ab:cd:ef:gh:12:34"
These logs show that the client was disassociated from AP-1 due to AP handoff and then reassociated with AP-2 for a better connection.
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