Issue link: https://read.uberflip.com/i/1428383
LoRaWAN 1.0.3 Specification ©2018 LoRa™ Alliance Page 44 of 72 The authors reserve the right to change specifications without notice. 11 Downlink Ping frame format (Class B option) 1192 11.1 Physical frame format 1193 A downlink Ping uses the same format as a Class A downlink frame but might follow a different 1194 channel frequency or data rate plan. 1195 11.2 Unicast & Multicast MAC messages 1196 Messages can be "unicast" or "multicast". Unicast messages are sent to a single end-device 1197 and multicast messages are sent to multiple end-devices. All devices of a multicast group 1198 MUST share the same multicast address and associated encryption keys. The LoRaWAN 1199 Class B specification does not specify means to remotely setup such a multicast group or 1200 securely distribute the required multicast key material. This must either be performed during 1201 the node personalization or through the application layer. 1202 Example: The document [RPD1] describes a possible application layer 1203 mechanism for over-the-air multicast key distribution. 1204 11.2.1 Unicast MAC message format 1205 The MAC payload of a unicast downlink Ping uses the format defined in the Class A 1206 specification. It is processed by the end-device in exactly the same way. The same frame 1207 counter is used and incremented whether the downlink uses a Class B ping slot or a Class A 1208 downlink slot. 1209 11.2.2 Multicast MAC message format 1210 The Multicast frames share most of the unicast frame format with a few exceptions: 1211 • They are not allowed to carry MAC commands, neither in the FOpt field, nor in the 1212 payload on port 0 because a multicast downlink does not have the same authentication 1213 robustness as a unicast frame. 1214 • The ACK and ADRACKReq bits MUST be zero. The MType field MUST carry the 1215 value for Unconfirmed Data Down. 1216 • The FPending bit indicates there is more multicast data to be sent. If it is set the next 1217 multicast receive slot will carry a data frame. If it is not set the next slot may or may 1218 not carry data. This bit can be used by end-devices to evaluate priorities for conflicting 1219 reception slots. 1220 1221