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Lwip delayed ack problem with demo example

Question asked by l.max on Dec 30, 2013
Latest reply on Dec 31, 2013 by francescato.diego
I am using STM3220-G Eval board.
Sample application  ST library - \STM32F2x7_ETH_LwIP_V1.1.0\Project\FreeRTOS UDP_TCP_Echo_server-netconn.
No any changes to the examples. No any changes to the board.
To test this app. I send with a maximal speed packets with length from 60 to 1460 bytes.
At the beginning it works perfect. But after while (hundreds thousands of packets) I see the speed is reduced. With ethernet scan I can see that STM32 have delayed TCP Ack for few seconds. As a result computer send TCP retransmition telegrams. And STM32 sends Dublicate TCP Ack.
As soon as Evaluation board got this state. It reacts the same way for any also single TCP telegram from computer. The Disconnection and reconnection once more do not solve the problem. I have to restart Evaluation board to reset this behavior.
TO reduce the problem source i have tested it in a direct connection (no any switcher).
I set on debug mode on Lwip - I didn't get any warning messages no fault messages. I can see all the telegrams comes to and from Lwip stack with a correct CRC. 

I tried to switch off the Nagle Algoritm - but it had no effect.

I will appreciate any help about.
Thank you.