[c-nsp] CEF memory usage

Rodney Dunn rodunn at cisco.com
Fri Oct 7 10:47:19 EDT 2005


Let me try and clear some confusion up here because as
I see a lot people make general observations and it explodes
to some "the sky is falling" scenario.

a) 12.3T does not have the changes to support MPLS NSF that
   went in to 12.2(22)S 
b) 12.2(22)S is the ONLY place where we made those improvements and
   yes they were improvements. There were some side effects such
   as increased memory usage, some bugs due to the new code, etc.
   With the release of 12.2SB when it comes out for the 72xx/75xx
   those memory usages should come back close to the numbers before.
   Now the memory usae I'm talking about is the per prefix usage
   by CEF and MPLS. The *base* memory usage of the image will increase
   because there are a lot more features coded in those images.

The overall throughput improvement of a box with multiple features
applied on various interfaces improved with the CEF changes also.
How much depends on the traffic profile/distribution through the
interfaces and the features configured. It was an improvement
in overall packet switching performance. It's very likely those
changes will show in i a future T release at some point such
as 12.4T.


Rodney


 

On Fri, Oct 07, 2005 at 10:17:11AM -0400, Joe Maimon wrote:
> OK
> 
> We have heard a lot on how 12.3T, 12.2(25)S have new CEF code that is 
> (extremely) memory inefficent.
> 
> Practicaly speaking that translates into difficulties doing BGP full 
> tables with previously sufficient RAM, like 256M on 7500's and 7200.
> 
> Is there any plan, DDTS, timeline, release, interim fix or any intention 
> to address this?
> 
> Is there a definitive list of images that can be used today w/o the new CEF?
> 
> Thanks,
> 
> Joe
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