Hello, Our 2008 server began to work very slowly within 2 weeks. Our web sites (iis 7.5) are loading very slowly and sometimes its freezing. We began testing with wireshark and saw that our packets are lost during transmission. The client demands the same packets several times, please check below. (CLIENT): 11 3.492500 Client Server TCP 54 61220 > http [ACK] Seq=316 Ack=5521 Win=66240 Len=0 (SERVER) : 12 3.495204 Server Client TCP 1434 [TCP Previous segment lost] [TCP segment of a reassembled PDU] (CLIENT):13 3.495225 Client Server TCP 66 [TCP Dup ACK 11#1] 61220 > http [ACK] Seq=316 Ack=5521 Win=66240 Len=0 SLE=6901 SRE=8281 (SERVER) :14 3.604038 Server Client TCP 1434 [TCP segment of a reassembled PDU] (CLIENT):15 3.604062 Client Server TCP 66 [TCP Dup ACK 11#2] 61220 > http [ACK] Seq=316 Ack=5521 Win=66240 Len=0 SLE=6901 SRE=9661(SERVER) :16 3.606074 Server Client TCP 1434 [TCP Previous segment lost] [TCP segment of a reassembled PDU] ... (CLIENT):23 3.714810 Client Server TCP 74 [TCP Dup ACK 11#6] 61220 > http [ACK] Seq=316 Ack=5521 Win=66240 Len=0 SLE=11041 SRE=16561 SLE=6901 SRE=9661 (SERVER) :24 3.718211 Server Client TCP 1434 [TCP Fast Retransmission] [TCP segment of a reassembled PDU] We cehcked the frames in detail and saw that majority of the errors are "IP checksum offload errors" . when we disable "Checksum offload" from our network adapter, then we began to receive lots of "suspected transmission" and server is still slow. Interesting thing is in one of our IP's in our server we are not receiving this error, and the web sites using that IP is rapid enough. Do you have any idea what is going on ? thanks in advance Kamil

Hi, Please make sure the server is up to date. Also install the latest driver of the NIC. In order to narrow down this issue, you can use individual NIC instead of this Network adapter. If the issue related to the NIC, you need to contact the NIC vendor support for further investigation. Your understanding is highly appreciated. Best Regards, AidenAiden Cao TechNet Community Support

Hi Aiden, Thank you for your reply. I am not very good at network issues. Would you please tell me how to test individual NIC ? thanks in advance

Hi, Do you have more than one NIC on this server? Have you configure the NIC teaming on this server? Is the NIC driver up to date? I mean if problem still persists, you may consider to using an alternate network adapter to test. To narrow down if the issue was cause by the specific NIC. Best Regards, AidenAiden Cao TechNet Community Support

Hi, Do you have more than one NIC on this server? Have you configure the NIC teaming on this server? Is the NIC driver up to date? I mean if problem still persists, you may consider to using an alternate network adapter to test. To narrow down if the issue was cause by the specific NIC. Best Regards, AidenAiden Cao TechNet Community Support

Hi Aiden, I talked with my hosting proveider, to change my NIC in the server and the problem solved. thank you for all your effort