OS choice for an edge router

[Claudio Jeker]

On Fri, Sep 07, 2007 at 04:56:22PM -0700, Bakul Shah wrote:
> > This is not the case.  Flood ping doesn't reach the limit in any
> > way.  Have a look at the ping man page and flood ping description.
> 
> Ah yes, I was forgetting about the strict synchrony.
> 
> > Stock FreeBSD 6.2 or 7.0 can easily do 500kpps with good network
> > cards and fastforwarding enabled.  On a dual-Opteron 2.6GHz with
> > PCI-X Intel and Broadcom network cards I've done 800kpps in-out.
> 
> What is the throughput when fastforwarding is not used and
> packets go to different destinations?  Note that typically
> fastforwarding does not help much on a router since only one
> route is cached.

Wrong. Fastforwarding does not cache routes, it is more a process-to-
completion frowarding bypassing a lot of unneeded code.

> 
> > > Listen to what Louis Mamakos said!  Use FreeBSD primarily for
> > > the control plane.  May be there are NICs where you can
> > > offload some packet forwarding.... But that is a substantial
> > > change to FreeBSD.  Or live with what FreeBSD can do on a
> > > given box.
> > 
> > There are no NICs known that can do packet forwarding offload.
> > And neither is there support in FreeBSD for that.  You're probably
> > confusing this with checksum offloading or TSO (TCP segmentation
> > offloading) which isn't an issue with packet forwarding at all.
> 
> Indeed.  That is why I said "that is a substantial change to
> FreeBSD"!  But even offloading checksum can help as the CPU
> has less to do.
> 

Wrong. A router only needs to check and update the IPv4 checksum and doing
that can be done in a few simple instructions. There is no need to look at
the TCP or UDP checksum. So in the end checksum offloading has little
effect on forwarding performance.

-- 
:wq Claudio