Re: ip_input - chksum - why is it done so early in ip_input?
From: Ruslan Ermilov (ru_at_freebsd.org)
Date: 01/17/04
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Date: Sat, 17 Jan 2004 02:35:41 +0200 To: Sten Daniel S?rsdal <sten.daniel.sorsdal@wan.no>
On Sat, Jan 17, 2004 at 12:50:04AM +0100, Sten Daniel S?rsdal wrote:
>
> Apologies for the cross-post, i wasnt sure if this was hackers or net material.
>
> I've often wondered why ip checksumming is done on every incoming
> packet and not only on the packets that need to be delivered locally.
> It looks like a very expensive way of doing it, especially on high
> PPS. Basically all hosts do checksumming so why not just pass the bad
> packet on, making the forward process alot cheaper (cpu wise)?
>
> I ran some tests (unable to disclose results) by removing it completely
> and it seems to make a noticable impact on the performance.
> Especially on for example gaming services where there is a high PPS versus
> actual data.
>
> Besides that i'd like to add that FreeBSD has the fastest forwarding engine
> i've seen on any free OS. It's in my opinion a very suitable OS for
> routing/forwarding.
>
Have you tried ``sysctl net.inet.ip.fastforwarding=1''?
It's documented in the inet(4) manpage.
Cheers,
-- Ruslan Ermilov FreeBSD committer ru@FreeBSD.org
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