[pptp-server] Severe performance problems

[Gianluca Insolvibile]

And that's a prompt answer! ;-)

pptpd.conf has 'option /etc/ppp/options.pptp'. This is /etc/ppp/options.pptp:

lock
debug
auth
+chap
+chapms
+chapms-v2
proxyarp
mppe-40
mppe-128
mppe-stateless

I have seen the recent thread on the 'speed' option, but I am not using that. In
my case, I suspect something strange is happening with TCP flow control over the
PPTP channel, but just can't imagine what.

Gianluca


George Vieira wrote:
> 
> Well that was a bible and a half ;-) kiddin', but very in depth...
> 
> What does you /etc/ppp/options.* say....
> 
> Your not using the speed option are you?
> 
> -----Original Message-----
> From: Gianluca Insolvibile [mailto:g.insolvibile at cpr.it]
> Sent: Wednesday, 12 December, 2001 8:06 PM
> To: pptp-server at lists.schulte.org
> Subject: [pptp-server] Severe performance problems
> 
> Hi to everyone,
> 
> I am fresh new to the pptp-server list, so please forgive me if I am missing
> some obvious points or asking an FAQ. I already tried digging into this
> mailing
> list archives with no success.
> 
> Briefly, my problem is this: I set up pptpd on a Linux box and had a Windows
> 98
> machine connect to it via an (unloaded) Ethernet LAN. Control-plane works
> fine
> (MS-CHAPv2, MPPE 128 bit, and the like), but the data-plane performance
> (roughly
> measured via iterated ftp's of a 51.2 MB file) is quite disappointing.
> 
> On the server side I tried a Pentium III 800 Mhz, a K6-II 400 Mhz and an
> Athlon
> 945 Mhz, whereas on the client side I had a Pentium 166 Mhz, a Pentium 233
> Mhz
> and a K6-II 400 Mhz. Network cards were 10 Mbps in some tests and 100 Mbps
> in
> the others. In all cases, with any combination of the above, I measured a
> 1.5
> Mbps maximum throughput (transfers from the Linux server to a single Windows
> client), that seems to me embarassingly low. I haven't even tried with more
> precise measurement tools (like netperf) since I believe the results would
> not
> change that much.
> 
> Software versions I am using are as follows:
> Linux kernel 2.4.16 + openssl-0.9.6b-mppe patch
> ppp-2.4.1 + MSCHAPv2-fix and openssl-0.9.6-mppe patch
> pptpd 1.0.1 and 1.1.2
> Windows 98 clients with various patches (DUN 1.4 upgraded)
> 
> As far as I can understand them, no strange messages are reported by either
> pptp, ppp or the kernel. Negotiated PCKT_RECV_WINDOW_SIZE, as reported by
> syslog, is 32. I tried changing that in ctrlpacket.c to 2, 4 and 8 (hoping
> at
> least to see performance decrease) with no evident changes in throughput.
> 
> I collected a packet trace with tcpdump and am going to analyze that; at a
> first
> glance, it seems that a lot of TCP segments are being transmitted with
> unusually
> high inter-packet times (in the order of 10 msec, IIRC). I still do not know
> if
> this depends on the Linux side or on the Windows side.
> 
> Now, before getting mad with the TCP trace, the PPTP RFC and the kernel
> code,
> does anyone have any ideas that may help ? Any hints would be really
> appreciated.
> 
> Thanks for the patience of reading my long mail! ;-)
> 
> Best Regards,
>         Gianluca Insolvibile