On Feb 8, 2013, at 12:25 AM, Hannes Gredler <[email protected]> wrote:

> tony,
> 
> agree that saving power is a worthwhile goal;
> 
> in fact existing hardware technology is making that happen today by
> e.g. automatically shutting down unused lookup engines, CPU cores, memory 
> banks etc.
> when there is low processing demand.
> 
> the part where i am not yet convinced is that additional off-peak 
> "optimization" of
> infrastructure links by e.g. computing a routing mesh which only uses
> 70% of the nominal links does actually give much power savings.
> 
> note that line cards which are running at 70% have already throttled down 
> their
> power consumption - so what is the point emptying the link and loading 
> another ?
> appears to me a zero sum game.
> 
> my concern about the core (and SP edge) is not about business or technology -
> it is more about if we try to optimize an already optimized (and solved) 
> problem.


If there are no more optimizations to be had, then talking about it isn't going 
to hurt anything.  

The point of emptying links is the ability to turn off NPUs (50-100W ea.), turn 
off edge optics (2-20W ea.) and most importantly turn off long-haul optics 
(100-400W ea.).  Yes, I realize that the latter part is really problematic 
because DWDM systems are balanced with all lambdas active, and that disabling 
any one of them can cause issues with other lambdas.  

Still, it would be nice to understand what CAN be done, if only to feel like 
we've truly explored every corner in the solution space and exhausted every 
option.

Tony

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