[pptp-server] speed issues

Frank Cusack fcusack at fcusack.com
Tue Mar 26 03:57:06 CST 2002

On Mon, Mar 25, 2002 at 09:55:16PM +0000, Barsalou wrote:
> We did a test and I am wondering if others are experiencing the
> same.  When downloading a file (size doesn't seem to matter it
> takes about 6 times as long using the VPN link as doing same via
> http or ftp.

How are you downloading over the VPN link?  What version of pptpd?
What link speeds are we talking about here?

>  What are some things that I can do to possibly speed things up?  
>  That seems like way more overhead than there should be.  I have 
>  played with the MTU's and stuff with out much effect.
>  I do get a lot of out of order packets.

That's to be expected.

>  Wouldn't that affect http and ftp the same though?

No.  And it shouldn't affect pptp; the server *should* queue out of
order packets.  However if your IP stack does TCP-SACK then it could
make a big difference.  I have to guess it is unlikely this is a factor.

If pptpd's windowing is simplistic or naive (I understand it to be at
least one of these) you will likely have problems with performance.

Looking through list archives, Patric Sandberg seems to be the man that
would know about these things, if he's still hanging around.


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