Host with IP 192.168.1.27 - my app on Linux. This is MODBUS-master. Host with IP 192.168.1.252 - MODBUS-slave. It is blackbox for me. Protocol MODBUS-TCP. Both devices linked by one wire, without any middle devices.
I see that Linux duplicates ack in frame #9 and do Spurious Retransmission in frame #10 after. And this situations repeat 3 times and Linux do reset after. What is possible reasons for sending duplicated ACKs and Spurious Retransmission from sender on Linux? This is TCP settings on Linux:
