LoRaWAN 1.1 Compatibility

The firmware embeds LoRaMac-node v4.6.0. That version supports two LoRaWAN protocol versions:

• LoRaWAN 1.0.4 Specification Package
• LoRaWAN Specification 1.1 (2017) together with the FOpts Encryption, Usage of FCntDwn erratum (2018)

The FOpts, FCntDown erratum addresses a critical security vulnerability in the LoRaWAN 1.1 protocol. If you use LoRaWAN 1.1 in your network, make sure your network server supports the modification described in the erratum.

The erratum modifies the encryption algorithm for the FOpts header field. If you network server does not support the modification, MAC commands (ADR, link check, device status, etc.) transmitted in the FOpts header field will be silently discarded. Thus, application-layer communication will work, but network-layer commands such as LinkCheck will fail. The MAC commands will only work if they are transmitted in the message payload.

The Things Network (TTN) network server as of v3.18.2 does not seem to implement the modification. Thus, if you use the firmware with TTN, make sure to select 1.0.4 as the protocol version for the device. Until TTN implements the modification, the firmware cannot be used with TTN in LoRaWAN 1.1 mode. The modification will be most likely included in LoRaWAN 1.1.1 (not yet published). Hopefully, TTN will implement the modification at that point.

Update from May 31, 2022: TTN stack v3.19.2 or newer implements the FOpts, FCntDown errata and one can thus select LoRaWAN 1.1.0 as the protocol version for the device in TTN. Tested with lora-modem-abz v1.1.1 and TTN v3.19.2.

The ChirpStack network server implements the modification. Thus, it should be possible to use the firmware in LoRaWAN 1.1 mode with ChirpStack.