# IPv6 Convergence for IoT Cyber-Physical Systems
## 5 Evaluation and Results  
Our experimental configuration, depicted in Figure 18, comprised a LoRaWAN endpoint, a gateway node, a LoRaWAN network server and a test client device capable of issuing IPv6 ICMPv6 requests. The LoRaWAN endpoint operated in the 868 MHz ISM band and was configured for Mode A operation with confirmed upstream messages. Our LoRaWAN gateway was connected to a network server via Ethernet. Our test IPv6 clients also connected to the network server via Ethernet. Multicast IPv6 requests were compressed and routed to the LoRaWAN endpoint via this  
Figure 16: Ultra-compressed IPv6 ICMPv6 message for LoRaWAN.  
Figure 17: Main processes involved for the downstream handling of ICMPv6 commands and LoRaWAN messaging.  
Figure 15: RoHC IPv6 header frame format.  
network server. A basic example of a multicast request is an echo request. We also conducted testing using the private experimentation fields (200, 201) as defined in RFC4443 [39].  
The ICMPv6 request and downstream messaging process via LoRaWAN is depicted in Figure 17. In this example, the ICMPv6 request handling and compression and LoRaWAN messaging are connected processes, and the stages performed by the endpoint are outlined in red. The network server was responsible for performing caching and compression of incoming multicast ICMPv6 commands and waiting for LoRaWAN upstream messages before appending the compressed commands to the downstream ACKs.  
In Figure 19, we provide an excerpt from the network server log where an upstream message has been received. The cached compressed ICMPv6 command, which was targeted for that specific LoRaWAN endpoint, is appended to the downstream ACK. In this example, the compressed IPv6 header, command and checksum octets are 0 xC0 0 xA1 0x61, respectively.  
Following this, Figure 20 is an excerpt of the LoRaWAN gateway log where the downstream packet has been scheduled for transmission, targeting the first receive window for the endpoint. The three bytes comprising the compressed ICMPv6 command have been appended to the LoRaWAN MAC frame field, as highlighted in this figure.  
Figure 19: LoRaWAN network server reports an upstream message.  
Figure 20: We prepare a LoRaWAN ACK containing a 3-byte ultracompressed IPv6 command, which is transmitted by the LoRaWAN gateway.  
In Figure 21, we depict a spectrogram showing the upstream message from the test endpoint and ACK waveform, with the appended compressed ICMPv6 command from the LoRaWAN network server one second later.  
In Figure 22, we present an excerpt from the LoRaWAN test endpoint indicating the received downstream message, and we highlight the received command structure within the downstream message.  
Through this initial experimentation, we were able to determine that IPv6 commands via further compression of 6 LoWPAN for support over very constrained networks is feasible. Our initial findings based on LoRaWAN experimentation, and outlined in Table 2, indicated that we could dispatch and receive ultracompressed IPv6 commands that were 27x smaller than the reported maximum PDU (or MTU) size of 81 bytes.  
Figure 21: A spectrogram depicting the upstream message and ACK from the LoRaWAN network server one second later.  
Figure 22: Received downstream bytes reported by a LoRaWAN test endpoint.