I'm using iperf to estimate network performance between Windows and Linux.

For TCP iperf shows 312 Mbits/sec from a Linux server to a Windows client, but it shows only 160 Mbits/sec from a Windows server to a Linux client.

For UDP iperf shows 147 Mbits/sec and 82% loss from a Linux server to a Windows client, but it shows 92 Mbits/sec and 0% loss from a Windows server to a Linux client.

I can't uderstand why iperf result is different when I change the direction from "Linux->Windows" to "Windows->Linux".

Could anyone please explain me why it happens and what is it related to? Thanks.

I have 1Gb network and: 1) Windows XP SP3, iperf 2.0.4 win32 threads; 2) Ubuntu 11.04 Server, iperf 2.0.5 pthreads


Sounds like either a speed or duplex mismatch. Check the duplex settings on both adapters. I would ensure they are set to auto-negotiate.

Per Greg Ferro "Gigabit Ethernet must have auto-negotation ENABLED to allow negotiation of master / slave PHY relationshitwhp for clocking at the physical layer. Without negotiation the line clock will not establish correctly and physical layers problems can result."

  • Thanks for the answer. My network adapter status is "connected, speed - 1Gbps" in Windows, but 'Speed&Duplex' property on 'Advanced' tab doesn't have 1000Mpbs value, just 10 and 100 Mbps (half/full). I have no idea what does it mean? Bad network driver or..? – Rom098 Sep 28 '11 at 13:41
  • Are you using a gigabit switch between the clients? – Fergus Sep 28 '11 at 17:01
  • I've asked my sysadmin for network configuration status. He is sure that we have 100Mbit switches in our network. But we've just found that routes are different for W->L and L->W. He doesn't know why, and he's trying to investigate it now. So it looks like we have network configutation issues, not Windows or Linux problems. Anyway, thank you again. – Rom098 Sep 29 '11 at 9:13

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.