Issue link: https://read.uberflip.com/i/1428350
LoRaWAN Remote Multicast Setup v1.0.0 Specification ©2018 LoRa Alliance™ Page 9 of 18 The authors reserve the right to change specifications without notice. ReqGroupMask. In that case the server can get the status of the groups not listed by issuing 223 a new McGroupStatusReq command with another RegGroupMask field. If all groups 224 requested can be listed, AnsGroupMask == ReqGroupMask. 225 226 NbTotalGroups is the number of multicast groups currently defined in the end-device. The 227 valid range is [0:4]. 228 229 Each record consists of 5 bytes [McGroupID + McAddr]. 230 McGroupID and McAddr are provided to the end-device by McGroupSetupReq. 231 4.3 McGroupSetupReq & Ans 232 233 This command is used to create or modify the parameters of a multicast group. 234 The payload of the message is: 235 236 Field McGroupIDHeader McAddr McKey_encrypted minMcFCount maxMcFCount Size (bytes) 1 4 16 4 4 Table 7: McGroupSetupReq 237 238 Where: 239 240 McGroupIDHeader Fields RFU McGroupID Size (bits) 6bits 2bits Table 8: McGroupSetupReq McGroupIDHeader field 241 242 McGroupID is the multicast group ID of the multicast context. An end-device MAY support 243 being part of several multicast group simultaneously. Therefore, all multicast related 244 command MUST always contain an identifier (the McGroupID) of the multicast group being 245 affected. 246 Note: The McAddr could be used as a multicast group identifier but this 247 would add a systematic 4 bytes overhead, so a more compact 248 McGroupID is used. Additionally, if MultiCast keys are kept in a 249 Hardware Secure Element that can only keep a few keys, the MCU 250 needs to indicate which key memory slot should be used. Therefore, 251 the Multicast group ID concept is required. 252 An end-device implementing this package SHALL support at least one multicast group. An 253 end-device MAY support up to a maximum of 4 simultaneous multicast contexts. 254 255 McKey_encrypted is the encrypted multicast group key from which McAppSKey and 256 McNetSKey will be derived. The McKey_encrypted key can be decrypted using the following 257 operation to give the multicast group's McKey. 258 McKey = aes128_encrypt(McKEKey, McKey_encrypted) 259 260 The McKEKey is a lifetime end-device specific key used to encrypt Multicast key 261 transported over the air (it is a Key Encryption Key), and may be either: 262 • Derived from a new root key (GenAppKey) provisioned in the end-device at any 263 time before the deployment of the end-device in the field. LoRaWAN 1.0.x end- 264 devices SHALL use this scheme. 265