The following figure as per IEEE P802.3 illustrates the position of the AN function in the OSI reference model.
The Auto-Negotiation IP core implements the requirements as specified in Clause 73, IEEE Std 802.3-2015, including those amendments specified in IEEE P802.3by and Schedule 3 of the 25 GE Consortium.
The functions of the AN IP core are explicitly listed in clause 73, especially in Figure 73-11, Arbitration state diagram, of section 73.10.4, State diagrams.
During normal mission mode operation, with link control outputs set to (bin)11, the bit operating frequency of the SerDes input and output is typically 10.3125 or 25.78125 Gb/s. However, the Dual Manchester Encoding (DME) bit rate used on the lane during auto-negotiation is quite a bit different than the mission mode operation.
To accommodate this requirement, the AN IP core uses over-sampling and over-driving to match the 156.25 Mb/s auto-negotiation speed (DME clock frequency 312.5 MHz) with the mission mode 10.3125 or 25.78125 Gb/s physical lane speed.