Best ethernet config for benchamrking on STM32H753

Hello, I hope you are doing well.

I am currently working on benchmarking the Ethernet communication interface on an STM32H753 Nucleo board.

My setup involves sending data from a Python script to the STM32, where the data is encrypted, and then sent back. This allows me to measure the RTT and overall throughput.

I initially used Mongoose, but I encountered several issues:

• With UDP, I cannot reliably send more than ~1500 bytes, since larger packets get fragmented or dropped.
• TCP works correctly, but the throughput varies significantly depending on payload size. For example:
  • ~2.7 MiB/s for 1400-byte payloads
  • ~7 MiB/s for 10240-byte payloads

I would like to know:

1. What is the best networking stack or library for STM32 to achieve better performance and properly handle UDP large payloads?
2. Given that Ethernet is 100 Mbps in my case, I am not reaching near-theoretical throughput even without encryption. Is this because I am measuring not only transmission time but also packet handling, buffering, and processing overhead (e.g., encryption, stack processing)? Is this assumption correct?

Thank you