Not all devices do the key rotation at the same time. This scenario fixes the issue when Router rotates sooner than SSED. In such case SSED still requires enhAcks to use previous key id and counter. Added storing last value of FC when keyId changes. If SSED uses keyId-1 ack uses the stored value instead of current mac counter value.
Not all devices do the key rotation at the same time. This scenario fixes the issue when Router rotates sooner than SSED. In such case SSED still requires enhAcks to use previous key id and counter. Added storing last value of FC when keyId changes. If SSED uses keyId-1 ack uses the stored value instead of current mac counter value.
Please see openthread/openthread#6688