[pptp-server] Severe performance problems

[Gianluca Insolvibile]

I posted that kind of data since I think it's not unlikely that different
versions/patches of kernel and pppd behave slightly differently (e.g.
out-of-sequence packet reordering, stateless MPPE, and so on). Hence,
performance may actually be affected by their version.

On the other side, my config files contain no parameters related to data-plane
handling of packets (except for 'speed', which I did not use anyway) and are
mostly related to authentication mechanisms, encryption, etc.

Gianluca

Robert Dege wrote:
> 
> I'm just curious, but would performance have to do with the version of
> ppp/kernel that users are using?  I don't remember people posting the
> versions of the PPP software that they were using, I remember more of
> their config files instead.
> 
> I'm using ppp-2.3.11 with Kernel 2.2.19, and I believe that I have a
> decent throughput.  Of course, despite transferring data via smb, I
> haven't really tested the total possible capabilities.  But I think I
> might test it today, just to see :)
> 
> -Rob
> 
> > Yes, actually I forgot to mention that performance in my case is not at all
> > influenced when I switch off encryption. The same even when passing from MPPE
> > 128 to MPPE 40.
> >
> > Gianluca
> >
> > George Vieira wrote:
> > >
> > > Yes this sounds true but rememeber alot of people having speed problems have
> > > switched off encryption and it still made no difference so that can't be the
> > > problem.
> > >
> > > thanks,
> > > George Vieira
> > > Systems Manager
> > > Citadel Computer Systems P/L
> > >
> > > -----Original Message-----
> > > From: Charlie Brady [mailto:charlieb at e-smith.com]
> > > Sent: Thursday, 13 December 2001 3:00 AM
> > > To: Gianluca Insolvibile
> > > Cc: pptp-server at lists.schulte.org
> > > Subject: Re: [pptp-server] Severe performance problems
> > >
> > > On Wed, 12 Dec 2001, Gianluca Insolvibile wrote:
> > >
> > > > 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.
> > >
> > > An interesting theory indeed.
> > >
> > > A google search for "nagle tcp" reveals a number of possibilities,
> > > including:
> > >
> > > http://www.icase.edu/coral/LinuxTCP.html
> > > http://support.microsoft.com/default.aspx?scid=kb;EN-US;q235624
> > >
> > > The key negotiation for MPPE might introduce significant latency, and that
> > > could affect the TCP transmission and retransmission timers.
> > >
> > > Remember too that PPTP packets must come in off the wire, go through the
> > > kernel, then into pptpd, then through the kernel and into pppd, then back
> > > through the kernel and into the application on the server. And vice versa
> > > on the way back out to the client.
> > >
> > > All this adds up to quite a lot of processing. Add to that 3DES
> > > encryption/decryption for each packet.
> > >
> > > Charlie Brady                         charlieb at e-smith.com
> > > Lead Product Developer
> > > Network Server Solutions Group        http://www.e-smith.com/
> > > Mitel Networks Corporation            http://www.mitel.com/
> > > Phone: +1 (613) 368 4376 or 564 8000  Fax: +1 (613) 564 7739
> > >