[c-nsp] Redirects / hair-pinning traffic vs. performance

[Rodney Dunn]

Curious..I don't know that platform forwarding architecture.

But what does 'sh int stat' give you?

Also, sh ip traffic a couple times once you start the traffic.


On Thu, Jun 18, 2009 at 07:13:02PM +0200, Peter Rathlev wrote:lso

> On Thu, 2009-06-18 at 00:01 +0000, Peter Rathlev wrote: 
> > I have the need to introduce some PBR to solve a hopefully temporary
> > problem. Some of the traffic being routed will leave the same interface
> > as it arrives on.
> > 
> > My worry is if this would have any performance impact the traffic
> > arrives on and leaves from the same interface. I could imagine that some
> > forwarding implementations might penalize this scenario.
> 
> Follow up: We've tested this and it works fine. It seems to have some
> CPU impact when the unit policy routes, but not much. When pushing 100
> mbps traffic through the CPU rises to ~25-30% for a few seconds (spent
> on interrupt switching) and then falls down ~5% again.
> 
> This might be PBR-specific and have nothing to do with the traffic
> arriving on and exiting the same interface though. We will be doing some
> more (production) testing soon, with more flows and more bandwidth. I
> can't see why the number of flows should matter since the 3560 AFAIK
> just pushes packets, but I also can't see why the start of a TCP session
> should matter. The "ip route-cache" hasn't been disabled of course; I
> assume this would have a detrimental effect on performance.
> 
> Regards,
> Peter
> 
> 
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