Speed limit of W5100S overhead

In the specification of the W5100s, the speed limit is said to be 25Mbps. On a bandwith limit of 100Mbps, does that include the protocol overhead. For example if half of my packet is the protocol overhead, would that mean that my limit is 12Mbps or 25Mbps?

This makes a pretty big difference in my budgeting and decision for the protocol. Most of my data packets are very small but the overhead would be >80% of the packets.

If the chip can actual transfer at 100Mbps and that the 25Mbps doesn’t include the overhead, than that means that I don’t have to worry much about the size of the protocol overhead.