[TriLUG] PoPToP VPN performance

[Jeremy Portzer]

On Mon, 16 Feb 2004, Ryan Wheaton wrote:

> Hey guys,
> 
> I've finally gotten my PoPToP VPN server to accept connections 
> correctly, and all seems to be dandy, but it is unbelievably slow.  I 
> couldn't get exact Mb/s times, but when I tried to copy the CentOS ISOs 
> (about 1.8Gb) to a file share over the VPN, it was going to take about 
> 23 hours.  I have a cable modem at home, so i'd expect that performance 
> would be considerably worse for dial-up users.  I expected it to be 
> slower than physically being in the office, but not THAT much slower.  
> Is this kind of performance expected?  Is there any way to tune the 
> server to improve performance?

Did you run a similar test without the VPN to compare?  Don't compare 
apples (local LAN speeds) to oranges (cable modems).

Remember that your cable modem upload speed is probably about 384 
Kbit/sec (at least that's the standard in this area for TWC).  1.8 GB is 
about 1932735283 bytes or 15461882266 bits.  Dividing by (384*1000), this 
makes a theoretical minimum transfer time of 39321 seconds, or 10.9 
hours.

Now, that estimate doesn't take into account : normal overhead of TCP/IP,
any other network traffic, etc.  Add the overhead of the VPN and a 23-hour
estimate is indeed a lot slower, but not off by THAT much, especially
since you may not have run the download long enough to get a good
estimate.  And my calculation is based on a 384 Kbit/sec upload rate,
which could be slower on your cable modem, changing the calculations quite 
a bit.

--Jeremy
 
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