Issue link: https://read.uberflip.com/i/1428383
LoRaWAN 1.0.3 Specification ©2018 LoRa™ Alliance Page 20 of 72 The authors reserve the right to change specifications without notice. If FOptsLen is 0, the FOpts field is absent. If FOptsLen is different from 0, i.e. if MAC 539 commands are present in the FOpts field, the port 0 cannot be used (FPort MUST be either 540 not present or different from 0). 541 MAC commands cannot be simultaneously present in the payload field and the frame options 542 field. Should this occur, the device SHALL ignore the frame. 543 4.3.2 Port field (FPort) 544 If the frame payload field is not empty, the port field MUST be present. If present, an FPort 545 value of 0 indicates that the FRMPayload contains MAC commands only; see Chapter 4.4 for 546 a list of valid MAC commands. FPort values 1..223 (0x01..0xDF) are application-specific. 547 FPort value 224 is dedicated to LoRaWAN Mac layer test protocol. 548 Note : The purpose of Fport value 224 is to provide a dedicated Fport to 549 run Mac compliance test scenarios over-the-air on final versions of 550 devices, without having to rely on specific test versions of devices for 551 practical aspects. The test is not supposed to be simultaneous with live 552 operations, but the Mac layer implementation of the device shall be 553 exactly the one used for the normal application. The test protocol is 554 normally encrypted using the AppSKey. This ensures that the network 555 cannot enable the device's test mode without involving the device's 556 owner. If the test runs on a live network connected device, the way the 557 test application on the network side learns the AppSkey is outside of the 558 scope of the LoRaWAN specification. If the test runs using OTAA on a 559 dedicated test bench (not a live network), the way the Appkey is 560 communicated to the test bench, for secured JOIN process, is also 561 outside of the scope of the specification. 562 The test protocol, running at application layer, is defined outside of the 563 LoRaWAN spec, as it is an application layer protocol. 564 565 FPort values 225..255 (0xE1..0xFF) are reserved for future standardized application 566 extensions. 567 568 Size (bytes) 7..22 0..1 0..N MACPayload FHDR FPort FRMPayload N is the number of octets of the application payload. The valid range for N is region specific 569 and is defined in the "LoRaWAN regional physical layer specification" document. 570 N should be equal or smaller than: 571 N ≤ M - 1 - (length of FHDR in octets) 572 where M is the maximum MAC payload length. 573 4.3.3 MAC Frame Payload Encryption (FRMPayload) 574 If a data frame carries a payload, FRMPayload MUST be encrypted before the message 575 integrity code (MIC) is calculated. 576 The encryption scheme used is based on the generic algorithm described in IEEE 577 802.15.4/2006 Annex B [IEEE802154] using AES with a key length of 128 bits. 578 The key K used depends on the FPort of the data message: 579 580