Re: Help with troubleshooting performance issue

Capture the data on the PPP interface and analyse it using Wireshark.
Look for retransmits.  PPTP may be failing to allocate kernel memory
for socket operations, and it should react by discarding the packet
rather than trying again.  PPP may be doing something similar.  If
there is packet loss, the TCP stream will slow down.

PPTP data is handled by a user-space process rather than by the kernel
alone, and so contention between the SCP and FTP processes and PPTP
may be cause.  Do the machines have multiple CPUs or only one?

PPTP wasn't originally designed with this I/O rate, so I'm surprised
you are even getting 4 or 5 MBps.  I have always observed a
performance degradation with PPTP.

Have you tried OpenVPN yet?

-- 
James Cameron
http://quozl.linux.org.au/

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