In Fig. 3.3 we first provide a quick look ahead at the overall handshaking process between a PSE and PD prior to power-up, as defined in IEEE 802.3af. We note that the PSE is initially just looking to confirm whether the device on the other side is an IEEE-compliant PD or not. Then it examines it further to estimate its power class. We recall that
Detection is the process by which the PSE asks: “Who are you?” (and the PD then presents its detection signature; akin to providing a thumbprint).
To this we now tentatively add the next part of the handshaking process, which will be discussed in more detail in the next chapter.
Classification is the process by which the PSE asks: “What are you?” [and the PD then declares its power-rating ...