Checksum Error LWIP

[Altera_Forum]

I am seeing checksum errors when using the cyclone development board (192.168.100.5) connected to a hub connected to my PC (192.168.100.5).  

 The error seems to add a 1 sec delay before it moves on. The delay is to much for my application.  Any idea how to address the issue or shorten the delay after checksum error is found?  I am using IDE Version: 1.1.0 Build: 137.   Here is the trace of the packets around the 1 sec delay using Ethereal. The communication is using TCP.  No. Time Source Destination Protocol Info  29475 33.995761 192.168.100.7 192.168.100.5 TCP [TCP Dup ACK 29474#1] 2662 > 4097 [ACK] Seq=1 Ack=20109313 Win=64240 Len=0  No. Time Source Destination Protocol Info  29476 33.996663 192.168.100.5 192.168.100.7 TCP [TCP Out-Of-Order] 4097 > 2662 [PSH, ACK] Seq=20108725 Ack=1 Win=2048 [CHECKSUM INCORRECT] Len=1460  No. Time Source Destination Protocol Info  29477 33.997276 192.168.100.5 192.168.100.7 TCP [TCP Previous segment lost] 4097 > 2662 [PSH, ACK] Seq=20110773 Ack=1 Win=2048 Len=588  No. Time Source Destination Protocol Info  29478 33.997300 192.168.100.7 192.168.100.5 TCP [TCP Dup ACK 29474#2] 2662 > 4097 [ACK] Seq=1 Ack=20109313 Win=64240 Len=0  No. Time Source Destination Protocol Info  29479 35.257149 192.168.100.5 192.168.100.7 TCP [TCP Retransmission] 4097 > 2662 [ACK] Seq=20109313 Ack=1 Win=2048 Len=1460

[Altera_Forum]

<div class='quotetop'>QUOTE </div> 

--- Quote Start ---  The error seems to add a 1 sec delay before it moves on. The delay is to much for my application.  Any idea how to address the issue or shorten the delay after checksum error is found?[/b]  --- Quote End ---    To be honest you need to look at the cause of the checksum errors, or provide a simple test case to reproduce it. If you really want to change the retransmission frequency, which I think will only move your problem the the function you need to look at is tcp_slowtmr in tcp.c.

[Altera_Forum]

Which checksum is Ethereal detecting as wrong - The &#39;frame&#39; checksum, or the TCP checksum ? 

 There was a known bug in the ethernet driver with bad TCP checksums on odd length packets which I reported on this forum a couple of months back - Search for "Checksum" - The thread was called something like "lanc911.c bug - and a fix".   - Roddy