[pptp-server] Giving up waiting for packets on LAN?

[Thorvald Natvig]

Greetings,

I'm using pptpd-1.1.2 with ppp-2.3.11 on Linux 2.2.19, plus the mppe
patches.

The VPN link works fine for normal 'low intensity' traffic, but as soon as
I start a full speed FTP transfer, the log on the server fills with:

May 30 22:23:28 eva pptpd[30516]: Buffering out-of-order packet; got 3178 after 3176
May 30 22:23:28 eva pptpd[30516]: Buffering out-of-order packet; got 3179 after 3176
May 30 22:23:28 eva pptpd[30516]: Buffering out-of-order packet; got 3180 after 3176
May 30 22:23:28 eva pptpd[30516]: Gave up waiting for 1 lost packets beginning with 3177
May 30 22:23:28 eva pptpd[30516]: Buffering out-of-order packet; got 3277 after 3275
May 30 22:23:28 eva pptpd[30516]: Buffering out-of-order packet; got 3278 after 3275
May 30 22:23:28 eva pptpd[30516]: Buffering out-of-order packet; got 3279 after 3275
May 30 22:23:28 eva pptpd[30516]: Gave up waiting for 1 lost packets beginning with 3276

(repeat a whole lot)

Naturally, speed crawls to almost nothing. Under WinME, about 250 kB/sec
is maximum, while Win2k manages up to 800-900 kB.

Normally, I'd credit this to actually lost packets, but the server and the
client are just on two different local VLANs, each connected to a 100Mbit
switched port, and there should be no dropped packets. Pingflooding,
extensive ttcp etc reveals no dropped packets, and the server CPU is never
loaded about 20-30%. If I just turn the VPN off, the same FTP transfer
strolls along with 8-9 MB / sec.

Any ideas on what's wrong and how I can fix it?