IPFW with user-ppp's NAT

Wojciech Puchar wojtek at wojtek.tensor.gdynia.pl
Sun Mar 16 17:25:28 UTC 2008

>> what's wrong in userland natd?
> Performance.  With userland natd, every packet that passes through natd
> must pass from kernel to userland (causing one context switch) and back
> again (causing another context switch).  This will be slower and use more
> CPU than doing it all inside the kernel, without any context switches.

true, anyway for my two 2Mbps symmetric connection (all for nat), and 
three 4/0.5Mbit connections (part for nat, mostly for squid) all natd 
processes takes at most 3 percent of single core (core2duo).

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