[pptp-server] performance tweaks

[Charlie Brady]

On Fri, 1 Feb 2002, Michael Barsalou wrote:

> What is the current thinking about performance problems.  We are
> getting lots of out-of-order packets.
>
> I looked through the archives and couldn't find any definitive
> solution or things to try and fix this problem.

The protocol is broken. It doesn't handle gracefully missing or out of
order packets. PoPToP 1.1.2 is a big improvement as it makes an effort to
reshuffle out of order packets.

PoPToP does not cause out of order packets. They are an unavoidable
consequence of multiple routing and congestion on the Internet.

> Here are the things that I believe will help:
>
> Setting the mru/mtu to 1450 in the pptpd.conf file
> removing the speed setting in the pptpd.conf file.

How would those things help? As far as I can tell the speed setting is
ignored.

> Anything else?

Only ever using PoPToP 1.1.2 is the most important thing that can be done.

Applying my patch and using stateful encryption may help, but at some
reduction in security. I don't know whether the patch will help or not,
but it does affect the response of the MPPE encryptor to missing or out of
order packets. The current PoPToP implementation is not compliant with the
published protocol - but only for stateful encryption, which is little
used.

--
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