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How exactly is 802.3af PoE auto-negotiated ?

How exactly is 802.3af PoE auto-negotiated ?

How exactly is 802.3af PoE auto-negotiated ?


My question is about the very low level specifics of the 802.3af (Power over Ethernet) standard. I want to know what changes 802.3af makes to the 1000BaseT autonegotiation procedure. Specifically does it alter the PHYs Base Page (aka Link Code Word)?
ie. for non-PoE 1000BaseT the Base Link Code Word it sends during autonegotiation will have the format:
bits [0:4] = Standard selector field
bits [5:11] = technology ability field
bit [12] = Extended Next Page
bit [13] = REF
bit [14] = ACK
bit [15] = Next Page
What I am trying to figure out is what changes (if any) were made to this format in 802.3af ? Does the setting of the 'Standard selector field' change to advertise that the PHY is PoE capable, or is this information encoded on the Next Pages with the Base LCW being left unaltered ?

Detailed question I know, but if anyone can answer it that would be great, thanks


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