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I installed PPTPD on both Redhat and ubuntu, and I found that the ubuntu is more slow than Redhat by testing, that is to say, Need I do some network optimization with Ubuntu?

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3 Answers

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We use FreeBSD as PPTP terminator because of fully in-kernel PPTP implementation, so it has no overhead for copying packets to and from userspace for en/decapsulation. Quad-core Xeon with hyperthreading handles near 400 users and 250Mbit of PPTP traffic in peak with load average near 2.5, but it needs good Intel network adapters to handle packets with low CPU usage.

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thanks!! could you tell me how do you know "so it has no overhead for copying packets to and from userspace for en/decapsulation." –  larry Jan 24 '11 at 12:57
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FreeBSD has netgraph framework, that allows to build any packet handling scheme from small blocks, each doing some simple operation(unix-way, yeah). All these blocks works fully in kernelspace and one more thing needed is a userspace daemon to handle incoming requests and connect these blocks together. Most popular such daemon is MPD (and possible only one existing) mpd.sourceforge.net –  gelraen Jan 24 '11 at 13:04
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" CPU: Intel(R) Xeon(TM) CPU 3.00GHz (3004.49-MHz 686-class CPU) FreeBSD/SMP: Multiprocessor System Detected: 8 CPUs FreeBSD/SMP: 2 package(s) x 2 core(s) x 2 HTT threads" and yes, server with this CPU and 2 Intel PRO/1000 network adapters really handles ~2 hour peak of 250MBit/s internet traffic on one interface and sends all this traffic encapsulated in PPTP via another interface. And LA at that time hangs near 2.5 –  gelraen Jan 24 '11 at 15:25
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Traffic accounted via netflow and statistics over last 5 minutes exported to Cacti. It is real traffic, not just testing trash. –  gelraen Jan 25 '11 at 9:22
    
I think "250MB" should be "250Mbit", right?, you know, 1B = 8b –  larry Feb 15 '11 at 2:13
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In response to your question - what exactly are you trying to achieve? You want to have a fast PPTP server, or are you picking between CentOS and Ubuntu?

In my experience, with things like PPTP, it's the overhead of the protocol that slows it down, so I generally either have a dedicated appliance just for PPTP, or bags of memory, and processor speed to compensate.

So much of the PPTP equation we can't account for, in fact most of it, because it's all coming from outside the network. I use a dedicated IP, and 1:1 NAT to help speed it up, (takes the load away from the firewall/gateway), and multiple gig nics.

Good Luck :)

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After a lot of problems, tests and trails we ended up with pfSense on a Fit-PC2i. This configuration has run for almost a year now with no down time, and good performance.

pfSense is based on FreeBSD. It is really easy to install and configure, even if you are not familiarly with BSD. It has intuitive web interface and runs on very limited hardware.

Fit-PC2i is a small PC, with an Intel Atom processor, two ethernet interfaces, 1 or 2 GB RAM and no moving parts. Perfect for router software like pfSense.

Happy PPTPing

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