On Fri, Oct 24, 2008 at 12:58:27PM +0200, Sebastian Reitenbach wrote:
> Hello everybody,
>
> I'm experiencing a very bad network performance, when I try to connect
> to a remote server.
> The point-to-point connection is a E3 line, with 34MBit/s, with a cisco 2800
> router on each side, terminating the point-to-point connection.
>
> These cisco routers have two gigabit interfaces, and a serial
> point-to-point E3 controller. Below my network layout:
>
> +-------------+
> |Remote Server|
> +-------------+
> |GigaBit Ethernet
> +------------+
> |Remote Cisco|
> +------------+
> |Serial E3 Line
> |
> +------------+ GigaBit Ethernet +---------+
> |Local Cisco |---------------------|Linux Box|
> +------------+ +---------+
> |GigaBit Ethernet
> +-------+
> |BSD Box|
> +-------+
>
> I use iperf to measure the connection speed.
> The OpenBSD box, and the Linux box are in two different networks,
> so the connection between these two is also routed.
> When I use iperf between the Linux-Box and the BSD-Box, then
> iperf measures about 500MBit/s, so thats fine.
> When I use iperf between the Linux Box and the remote server,
> then I get sth. about 32 MBits, that's fine too.
> When I use iperf between the BSD box and the remote server,
> I only get 2MBit/s.
> Then I thought, maybe the interface where the BSD box is connected
> is the problem, so I connected it to the interface on the cisco,
> where the Linux box was connected before, but still only the
> 2MBit/s speed to the remote host.
> I also tried different OpenBSD boxes, with different network adaptors,
> one with bge, another one with fxp, but also, no difference.
> With both BSD boxes, connection to the Linux box is fast,
> connections to the remote server is slow.
> Then I tried to fiddle around with pf, scrub rules on the BSD box.
> I tested with disabled firewall, with
> scrub no-df
> scrub set-tos lowdelay
> scrub set-tos throughput
> and some more, but without any observable difference in the speed.
> The Linux box and the BSD boxes both had the same MTU on their interfaces,
> and also no dropped packets, or errors on the interfaces.
>
> When I connect the Linux box behind the OpenBSD box, and then try to connect
> from the Linux box to the OpenBSD box, the performance becomes slow.
>
> So right now I'm a bit puzzled, and have no idea, why the connection to the
> remote host is fast when using a Linux box, but so slow when using OpenBSD.
> Are there any differences in the IP packets that OpenBSD and Linux creates?
> I'm going to capture the network traffic on the Linux and OpenBSD box to be
> able
> to compare the IP packets.
> Is there any tool where I can replay the packet sequence on OpenBSD that I
> have
> recorded with tcpdump on the Linux box?
>
> Unfortunately, I don't have access to the remote cisco, or remote
> server, so I cannot check anything there.
>
> any hint is greatly appreciated.
OpenBSD uses a pretty low default send and receive buffer size for
sockets. Try increasing net.inet.tcp.recvspace and
net.inet.tcp.sendspace, after reading a bit about bandwidth * delay
products.
-Otto
>
> If there is more information needed from my side, to explain the problem,
> don't
> hesitate to ask.
>
> kind regards
> Sebastian
>
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