Software router state of the art

Florian Weimer fw at
Mon Jul 28 20:42:08 UTC 2008

* Joe Greco:

> I'm not sure where the claims about "{one, few} flow{s}" are coming from.
> Certainly the number of flows on a typical UNIX box acting as a router is
> not that relevant unless you specifically configure something like 
> stateful firewalling, because the typical UNIX box simply doesn't have a
> *concept* of "flows."  It deals with packets.

You are mistaken.  Linux routing is flow-based.  Ever wondered what
those "dst cache overflow" messages mean you see during a DoS attack?
It's the flow cache complaining that it can't expire records in an
organic manner.

I don't know much about FreeBSD.  I think it got a route cache after
FreeBSD 4, too.  That's the reason why the FreeBSD 4 IP stack is still
so popular.

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