Re: Fast v.s classic forwarding in NetBSD 4.0

[Putrycy <putrycydestengier%gmail.com@localhost>]

Thank you very much for your answer. Explaination is clear, id like to
ask another questions though..

Which of those mechanisms is used by default ? Where to find any
documentation ? Is fast forwarding
fully functional in terms of working with advanced features, like
IPSEC, or are there any known problems
about FF ? Thanks A LOT.

P.

2010/7/12 Joerg Sonnenberger <joerg%britannica.bec.de@localhost>:
> On Fri, Jul 09, 2010 at 01:15:58PM +0200, Putrycy wrote:
>> Im having problems understanding relation between "classic"
>> (ip_input.c) and fast (ip_flow.c) forwarding. Could
>> anyone please explain what exactly is the difference, which mechanism
>> is used when, and what is corelation between those two ?
>
> ip_input.c does a full routing table look up for every packet. It has a
> single entry cache for the most recently used route, but that is
> normally not very efficient.
>
> ip_flow.c does flow-table based routing. It does a lookup for the packet
> header in an rb-tree and if it finds an entry, it uses the cached route.
>
> The primary difference between fast forwarding and normal forwarding is
> that the former traverses a bit less of the network stack and is quite a
> bit more efficient if there is a reasonable small to medium set of
> active connections AND the number of routes is high. I doubt it makes a
> different for a home router.
>
> Joerg
>