[pptp-server] Severe performance problems

[Gianluca Insolvibile]

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
>