I&#39;ve been trying to narrow down where my performance bottleneck(s) is (are). I just ran &quot;iperf&quot; from a Windows PC (XP SP3) to my Ubuntu 9.10 server. With iperf in &quot;server&quot; mode on the PC, and the client running on the Ubuntu machine, I get<div>
 0.0-60.0 sec  4.23 GBytes   606 Mbits/sec</div><div><br></div><div>Reversed (iperf &quot;server&quot; running on Ubuntu server, client running on the PC), I get</div><div> 0.0-60.0 sec  1.13 GBytes   162 Mbits/sec</div><div>
<br></div><div>Wha...?? Both client and server runs on the PC report TCP window size to be 8 KB, but the Linux client reports 22.4 KB and the Linux server reports 85.3 KB. Increasing that to 256K on both ends has little effect. Does anyone have any suggestions?</div>
<div><br></div><div>The Windows NIC is a Realtek RTL8169/8110 Family Gigabit Ethernet; the Ubuntu server is using the Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 01). Time to replace a NIC or two?</div>
<div><br></div><div>Kevin</div>