Hi,
myproblem was caused by a performance issue within the linux kernel
version used ( https://bugzilla.kernel.org/show_bug.cgi?id=74051 ) so it
is solved by using a more current kernel version or explicitely applying
the corresponding patch to the kernel.
Regards
Bernhard
Am 13.08.2015 um 10:07 schrieb Bernhard Dick:
> Hi,
>
> currently I see big performance problems with TCP connections within an
> OpenVPN tunnel. The OpenVPN server is connected via UMTS, on that
> connection I get about 2MBit UL and 10MBit DL rate.
> Inside the tunnel I get a quite good download speed (client -> server),
> the upload speed (server -> client) however is terrible, iperf gets
> about 30-80 KBit/s the tunnel via TCP. UDP traffic inside the tunnel is
> nearly at the speed of the UMTS connection.
> With wireshark I see a lot of TCP retransmissions on the tunnel
> interface, most of them leading to duplicate ACKs. Tcptrace shows me a
> RTT of about 800ms inside the tunnel, ICMP requests however are showing
> about 70-80ms.
> The problem is independent of the OpenVPN connection type (udp or tcp)
> being used. I also experimented with the fragment, mssfix, tun-mtu and
> link-mtu siwtches, they didn't help either.
> Do you have any ideas how to improve the TCP performance?
>
> Regards
> Bernhard Dick
>
--
Bernhard Dick, Dipl. Informatiker
S.E.A. Datentechnik GmbH
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Tel.: +49 2241 12737-55
Fax.: +49 2241 12737-14
E-Mail: bernhard.d...@sea-gmbh.com
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