My first post on Xen-Users, so ..
i've discovered a strange problem.
-A Windows server 2003R2 (x86) with GPL PV driver 0.9.9
ipferf 1.7.0 (from 2003)
-dom0 a opensuse 11.0 xen:
# rpm -q -a |grep -i xen
-1 interface as trunk on dom0, with some vlans's and xen bridges
-1 test machine in same subnet as the domU windows 2003 server.
on testmachachine: iperf -c <domU-IP> -p 2000
on domU iperf.exe -s -p 2000
gives great performance, about 850Mbit/s
The other way around:
on domU iperf -c <test-machine-IP> -p 2000
on test machine; iperf -s -p 2000
gives dramatically low results like 50KBit/s (no typo!)
same tests as above but instead of a remote test machine using to dom0
gives values beyound our physical limit (1.5GBit/s) in both ways.
(That may lead to a conclusion the something is wrong with the physical
network, but it's not, see point 4 )
4) iperf tests in both directions from dom0 to the remote machine are just
excellent. So nothing seems wrong with the physical network.
After some research i found exceptional many transmit tcp checksum
errors. for that i:
-disabled all NIC offloading on the test machine (ethtool -K ethx ... off)
-disables all NIC offloading on dom0 (ethtool -K ethx .... off)
-and finally disabled offloading in gplpv driver settings (gui)
-just to be sure also created a registry setting to disable NIC offloading
And still, after all this , while sniffing (tcpdump) on the virtual
interface at the dom0 (vifx.0) the first syn packet seems to have a
correct checksum, but the next packet (ACK 3th packet in tcp 3-way
handshake) has an incorrect checksum.
All folowing packets that are transmitted have all tcp checksum errors
So exept for the first outgoing SYN no other correct TCP checksum packets
seems to leave the system.
An other test met simple ftp results in terrible slow uploads (from domU
to test machine)
I did't investigate this ftp further, however it intreges me why from my
findings _any_ data gets transferred
just created a tcpdump on the vif of the ftp session, and found by the eye
no packet without checksum error. the relative acknowledge numer is in all
transmitted packets '0'.
While using the regular realtek NIC driver in xen i got a TX and RX
performance from about 85Mbit/s witch is acceptable for a 100MBit/s NIC
emulation, but not for the perpose i want to use (Gbit)
I also tried to sniff in the domU itself, but the M$ monitor tool seems
just not to see the NIC. didn't try winpcap/wireshark yet.
Any thoughts, experiences solutions?
Many thanks in advance
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