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Hello all,

I am trying to set up a 10Gig Ethernet system between an FPGA and a Windows 7 PC. The FPGA sends UDP packets to the PC continuously and that works fine. I have written a WinSock application in the PC which just receives the packets and sends a UDP packet to the FPGA once it received 'X' number of packets. Here is the problem:

The Windows PC is sending 128 packets to the NIC for every single packet that the PC application sends. Let me simplify. When the PC application sends N packets, I see N*128 packets at the FPGA end. When I checked the packets with Wireshark, I found that in those 128 packet set, the TTL and the IPv4 Header Checksum are the only fields that change. The TTL decreases to 1 and eventually the packet is destroyed. I really can not understand the behaviour. I am sure my PC application is not buggy because, I tried sending UDP packets from a tool I found online and the same behaviour repeats. Also, this behaviour is true for PINGs as well.

So, somehow the PC is giving 128 packets to the NIC for every packet generated by the PC App.

FYI, I have done some tweaks to the NIC properties such as IPv4, UDP checksum offloading and enabling RSS. I have increased the Rx Buffer to 40000 and enabled Jumbo Frames. This is to achieve max data rate.

I am a beginner in Ethernet. Could anyone please explain this strange behaviour.

asked 06 Apr '16, 04:08

vinaymv's gravatar image

accept rate: 0%

closed 06 Apr '16, 04:36

Jaap's gravatar image

Jaap ♦

The question has been closed for the following reason "Question is off-topic or not relevant" by Jaap 06 Apr '16, 04:36

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question asked: 06 Apr '16, 04:08

question was seen: 616 times

last updated: 06 Apr '16, 04:36

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