[CentOS] OpenVPN throughput

Fri Aug 20 22:02:09 UTC 2010
Gordon Messmer <yinyang at eburg.com>

On 08/20/2010 09:44 AM, Boris Epstein wrote:
>
> Gordon, thanks, very helpful.

No problem.

> I thought ethernet NIC's limit MTU to 1500. Just tried to set mine to
> 9000 and failed - it is OK with values<= 1500 though.

Depends on the cards.  In order to use (or take advantage of) jumbo 
frames, all of the network gear between two hosts must support it and 
must be configured to use it.  More importantly, all of the equipment on 
any ethernet segment must have the same MTU.

Gigabit equipment often performs much better when using jumbo frames, 
but you basically must dedicate an entire LAN to the use of jumbo frames 
in order to use it at all.  The router for that segment normally 
fragments the packets for use on lines that don't support jumbo frames.

It's unlikely that your two hosts have jumbo frame support between them, 
but only your ISP would be able to tell you that for certain.  I 
provided benchmarks that were more or less ideal.  Faster CPUs or 
hardware encryption accelerators will get you closer to full gigabit speed.