PPTP-Client constantly buffering packets

[idea4IT]

Hey guys,

I'm having issues with my pi that I'm using as a VPN gateway to my uni's network.
My pi is running dnsmasq, hostapd and ppptclient/pptp-linux, the hotspot part is working fine but I'm having performance issues with the pptp connection (ppp0).

Here's what I'm getting on archlinux and on raspbian:

Jan 01 01:14:48 alarmpi pptp[322]: anon log[decaps_gre:pptp_gre.c:414]: buffering packet 12573 (expecting 12544, lost or reordered)
Jan 01 01:14:48 alarmpi pptp[322]: anon log[decaps_gre:pptp_gre.c:414]: buffering packet 12574 (expecting 12544, lost or reordered)
Jan 01 01:14:48 alarmpi pptp[322]: anon log[decaps_gre:pptp_gre.c:414]: buffering packet 12575 (expecting 12544, lost or reordered)
Jan 01 01:14:48 alarmpi pptp[322]: anon log[decaps_gre:pptp_gre.c:414]: buffering packet 12576 (expecting 12544, lost or reordered)
Jan 01 01:14:48 alarmpi pptp[322]: anon log[decaps_gre:pptp_gre.c:414]: buffering packet 12577 (expecting 12544, lost or reordered)
Jan 01 01:14:48 alarmpi pptp[322]: anon log[decaps_gre:pptp_gre.c:414]: buffering packet 12578 (expecting 12544, lost or reordered)
Jan 01 01:14:48 alarmpi pptp[322]: anon log[decaps_gre:pptp_gre.c:414]: buffering packet 12579 (expecting 12550, lost or reordered)
Jan 01 01:14:48 alarmpi pptp[322]: anon log[decaps_gre:pptp_gre.c:414]: buffering packet 12580 (expecting 12552, lost or reordered)

After some internet research, I found out that there seems to be a problem with the mtu settings. But decreasing the mtus off all involved network adapters to 1416 doesn't solve the problem.
And adding the "--nobuffer" flag ends in:

Jan 01 01:16:41 alarmpi pptp[380]: anon log[decaps_gre:pptp_gre.c:414]: accepting packet 3502 (expecting 3501, lost or reordered)
Jan 01 01:16:41 alarmpi pptp[380]: anon log[decaps_gre:pptp_gre.c:414]: accepting packet 3504 (expecting 3503, lost or reordered)
Jan 01 01:16:41 alarmpi pptp[380]: anon log[decaps_gre:pptp_gre.c:414]: accepting packet 3507 (expecting 3505, lost or reordered)
Jan 01 01:16:41 alarmpi pptp[380]: anon log[decaps_gre:pptp_gre.c:414]: accepting packet 3510 (expecting 3509, lost or reordered)
Jan 01 01:16:41 alarmpi pptp[380]: anon log[decaps_gre:pptp_gre.c:414]: accepting packet 3512 (expecting 3511, lost or reordered)

Any ideas? Does anyone have further tricks how to improve my pi's network performance?

Cheers
Fabio

[idea4IT]

I think I fixed it myself. After disabling any overclocking config, the pptp-client doesn't buffer packets anymore but I'm still having performance issues.

When pptp is turned off, I get 1.2 MB/s which is the maximum but if it is turned on, I get around 300-700 KB/s and the connection is very inconsistent.

Any ideas, how to increase and stabilize the network/vpn performance?

Cheers
Fabio