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RE: [Xen-users] a lot of packet loss

To: Attila Szamos <szamosa@xxxxxxxxx>
Subject: RE: [Xen-users] a lot of packet loss
From: "Fischer, Anna" <anna.fischer@xxxxxx>
Date: Fri, 1 May 2009 23:50:06 +0000
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Thread-topic: [Xen-users] a lot of packet loss
> Subject: Re: [Xen-users] a lot of packet loss
> 
> I tried another tcpdump-thing.
> 
> I pinged from the VM to another non-xen-kernel machine. I ran a
> tcpdump on the xen host machine and the ping-target machine. The point
> is that on the host machine, on which the ICMP packets flow through:
> 
> 01:29:53.075672 IP perftest-vm2 > perftest7: ICMP echo request, id
> 24077, seq 8, length 64
> 01:29:53.075841 IP perftest7 > perftest-vm2: ICMP echo reply, id
> 24077, seq 8, length 64
> 01:29:54.075686 IP perftest-vm2 > perftest7: ICMP echo request, id
> 24077, seq 9, length 64
> 01:29:54.075884 IP perftest7 > perftest-vm2: ICMP echo reply, id
> 24077, seq 9, length 64
> 01:29:55.075700 IP perftest-vm2 > perftest7: ICMP echo request, id
> 24077, seq 10, length 64
> 01:29:55.075926 IP perftest7 > perftest-vm2: ICMP echo reply, id
> 24077, seq 10, length 64
> 01:29:56.075715 IP perftest-vm2 > perftest7: ICMP echo request, id
> 24077, seq 11, length 64
> 01:29:57.075728 IP perftest-vm2 > perftest7: ICMP echo request, id
> 24077, seq 12, length 64
> 01:29:58.075742 IP perftest-vm2 > perftest7: ICMP echo request, id
> 24077, seq 13, length 64
> 01:29:59.075761 IP perftest-vm2 > perftest7: ICMP echo request, id
> 24077, seq 14, length 64
> 01:30:00.075769 IP perftest-vm2 > perftest7: ICMP echo request, id
> 24077, seq 15, length 64
> 01:30:01.075783 IP perftest-vm2 > perftest7: ICMP echo request, id
> 24077, seq 16, length 64
> 01:30:02.075798 IP perftest-vm2 > perftest7: ICMP echo request, id
> 24077, seq 17, length 64
> 01:30:03.075812 IP perftest-vm2 > perftest7: ICMP echo request, id
> 24077, seq 18, length 64
> 01:30:04.075825 IP perftest-vm2 > perftest7: ICMP echo request, id
> 24077, seq 19, length 64
> 01:30:05.075840 IP perftest-vm2 > perftest7: ICMP echo request, id
> 24077, seq 20, length 64
> 01:30:05.075987 IP perftest7 > perftest-vm2: ICMP echo reply, id
> 24077, seq 20, length 64
> 01:30:10.082287 IP perftest-vm2 > perftest7: ICMP echo request, id
> 24077, seq 21, length 64
> 01:30:10.082448 IP perftest7 > perftest-vm2: ICMP echo reply, id
> 24077, seq 21, length 64
> 01:30:11.079923 IP perftest-vm2 > perftest7: ICMP echo request, id
> 24077, seq 22, length 64
> 
> On the perftest7 machine if a packet arrives, it gets a reply. So it
> seems that the packets are lost on the network. It imples that the
> problem is with the network, but If I dont use domU-s, there is no
> unreplied packets.

Well it depends. It could be that those lost packets actually never leave Dom0. 
Do you see them going out on the physical interface (e.g. peth0 or something 
like that) on Dom0 ?

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