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
Mülheimer Strasse 7
53840 Troisdorf
Tel.: +49 2241 12737-55
Fax.: +49 2241 12737-14
E-Mail: bernhard.d...@sea-gmbh.com
Web: www.sea-gmbh.com
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