Understanding Multi-Link Operation (MLO)

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Multi-Link Operation (MLO) is a key feature of WiFi 7, offering significant advantages in throughput and latency by allowing devices to connect to an access point using multiple radios simultaneously. MLO enables devices to connect to an access point (AP) using multiple frequency bands at the same time, such as 2.4 GHz, 5 GHz, and 6 GHz.

Advantages of MLO

1. Increased Throughput:
   • By utilizing multiple radios simultaneously, MLO can aggregate the throughput, significantly increasing the data transfer rate.
2. Reduced Latency:
   • MLO allows the AP to select the least busy radio, reducing latency by avoiding congested channels.

How MLO Works

1. Unique MAC Addresses:
   • Each radio on a device using MLO will have a unique MAC address.
   • Additionally, the device will have an MLD (Multi-Link Device) MAC address, which is recognized by other network devices.
2. AP Broadcasting:
   • Each radio on the AP broadcasts its own beacon using its radio MAC address.
   • These beacons include an information element indicating MLO support.
3. Connection Establishment:
   • A client device starts by connecting to the AP using a single radio.
   • During the negotiation, it informs the AP of its MLO capabilities and establishes a multi-link connection using multiple radios.
4. Encryption Keys:
   • Unicast traffic uses the same encryption key across all radios for a single client.
   • Multicast and broadcast traffic use separate keys for each radio.

MLO Traffic Handling

1. Traditional Wireless Traffic:
   • Traditional wireless traffic between a client and AP uses source and destination MAC addresses along with transmitter and receiver addresses in the wireless frame.
2. MLO Traffic:
   • In MLO, each radio has a unique MAC address. The AP uses the MLD MAC address for routing traffic across different radios.
   • When traffic moves from the wireless to the wired network, the AP translates the radio MAC address to the MLD MAC address.

Key Considerations

1. AP Configuration:
   • MLO settings can be enabled in the SSID advanced settings under the Nebula Control Center (NCC).
   • MLO is only available for cloud-managed devices
   • Only WiFi 7 APs support MLO.
2. Roaming:
   • Roaming between WiFi 7 and older standards (WiFi 6, 5) will require reassociation due to different MAC addresses.
   • This can lead to slower reconnection times.
3. Supported Features:
   • Supported: MAC authentication, MAC filtering, RSSI threshold, and load balancing.
   • Not Supported: WiFi 6 features like WiFi 6e, band steering, fast roaming (802.11r), smart mesh, accounting, and rate limiting.

Displaying MLO Information

• Client Page: The client page in NCC will show the MLD MAC address and the highest connected band.
• CLI Commands: Administrators can use CLI commands to view detailed MLO settings and verify configurations.

Example Use Case

• Scenario: A device connected via both 5 GHz and 6 GHz radios experiences one radio link drop.
• Impact: The entire multi-link connection will disconnect, requiring reestablishment of the connection.

Conclusion

MLO in WiFi 7 introduces substantial improvements in network performance by enabling simultaneous multi-band connections. Understanding and configuring MLO correctly can significantly enhance network efficiency, reduce latency, and increase throughput.