SDN Network – What is a Logically Centralised Controller?

So I haven't used the CMX APIs, but i can answer your first question regarding RSSI. So RSSI is a measure of signal strength. Basically the higher the number the stronger the radio signal strength. I do have a lot of experience setting up Meraki's wireless APs as well as troubleshooting Wireless issues. An RSSI value less that 40 usually means a poor signal and usually means that the client either cant connect to the network, or has intermittent data loss.

For your context, in general CMX triangulates where a client is in a wireless space by using the reported RSSI values coming from the various APs. As long as the APs are placed in the Meraki portal in the correct location on the floor map the dashboard will be able to triangulate an estimated position. I would imagine the raw data you are receiving is what the dashboard gets pre triangulation calculations.

Hopefully I helped your understand of RSSI values.

OpenFlow specifically - but also generally applicable to all of SDN - doesn't change anything about how your physical device forwards packets. The hardware is the same, and the pipeline that already existed on that device is unchanged.

What OpenFlow does is move the logic for programming the packet matches and actions from on the device itself (the local firmware), to a process that is running on a different device, which may have a view of more than one network element (and thus may be able to make better decisions with a better view of the world - or not). So, while you may configure network routing at a single controller, the controller is then distributing that information to a lot of devices to do what they have always done - match, modify, and forward packets.