Problems on windows
Hi,
We are using iperf as one of the underlying tools in the SURFnet
Detective (detective.surfnet.nl) and I'm seeing some really strange
behaviour. In our setup we have a bunch of linux servers on 1 GBit, and
when testing from linux clients over the WAN we get between 300-800mbit
depending on how many threads, window size etc (using TCP).
Using iperf 2.01 on windows I don't get more than 20 mbit. Using the -P
option crashes that version. Nevermind, I downloaded version 2.02 based
on cygwin, and decided to test some more from home. Home is an ADSL2+
connection 12mbit down, 1mbit up.
Surprisingly, when running iperf 2.02 with multiple threads, my upstream
bandwidth grows as I add more threads. With 1 thread it's 0.70Mbit, but
with 4 threads and a window size of 512k I get 2 mbit, this climbs to
3mbit upstream with 20 threads. With my ADSL2+ this simply isn't
possible (1mbit upstream max), so I suspect "something is wrong".
This puts me between a rock and a hard place:
1) multithreaded client (TCP) on WinXp looks unreliable, at least in the
ADSL range
2) single threaded (TCP) on high bandwidth networks is at least an order
of 10 lower on WinXP then the Linux box sitting next to it on
high-bandwidth networks.
Has anybody else observed this behaviour, or even better, has anybody a
solution for this?
Thanks!
Maarten Koopmans
Manager Middleware Services
SURFnet