RE: Related to Thread cloud coap client and NCP

Jørgen Holmefjord — Thu, 28 Mar 2019 14:04:33 GMT

Hi,

It is correct that the example use CoAP POST method to update cloud data, but this packet is sent directly to the cloud, not to the Border Router.
Thread runs IPv6 natively, and use IPv6 routing mechanisms to send packets to the correct device. The example does not find the IPv6 address of the Border Router, but all nodes in the Thread network are assigned global IPv6 addresses by the border router when this is attached to the network. The border router will create a IPv6 subnet from its own global IPv6 address, meaning that all nodes in the Thread network will know that the border router is where all packets addressed to nodes outside the subnetwork should be directed. The IPv6 address of the cloud service is retrieved using DNS service and URL.
The NCP example is a network co-processor, that is used to give the border router Thread connectivity. The NCP does not resolve the messages, only receives and forwards IPv6 packets. When a packet is received by the NCP, it is transferred to the Raspberry Pi through the serialization interface Spinel. The border router forwards the packet from the Thread interface to the Ethernet/WiFi interface without processing/modifying the packet. All happens on IPv6, and the packets are addressed directly to the end-point. Similar the cloud service can address response packets directly to the IPv6 enabled Thread end-device.

Best regards,
Jørgen