W5500 Ethernet module

Hello,

I’m using a W5500 module with 27Mhz of STM32 SPI clock and I’m sending 1800 bytes every 8ms for 20 seconds. I have created a private network, the module is connected to the laptop and in the module’s physical configuration I have set 100Mbps speed. After 20 seconds, should have received 2500 packets but some packets are missing and I have checked the speed with Wireshark which is around 200KBPS to 230KBPS. And when I checked with 1460 bytes, the speed comes down to 30KBPS.
So why I’m not getting actual speed?

Thanks.