[e2e] Changing dynamics

Pekka Nikander pekka.nikander at nomadiclab.com
Sat Feb 21 23:53:23 PST 2009

>> Instead of trying to optimise some queues in an end-to-end fashion  
>> and fighting of whether the optimal queue size is 1 or 4, perhaps  
>> we should aim to keep the fibers bitted up all the time, and all of  
>> the memories filled with usable data?  Isn't lit but idle fiber or  
>> powered but unfilled storage essentially waste?
> You cheated and said "powered" - but in general, no, there are cost/ 
> green reasons to not use things when you don't need to.

Oh, I may be wrong, but my understanding is that you cannot easily  
power up and down parts of RAM, parts of a hard disk, or fast enough  
the sending LED on a fiber.

It may also turn out that the opportunities to cut user-perceived  
latencies (such as in downloading) may have greater benefits than what  
the marginal energy savings would be from powering down partial  

>> Are we seeing a Content Wall joining the well-known Memory Wall?
> It's not a content wall - it's the speed of light.  As the saying  
> goes, "2.99 x 10^8 m/s: It's not just a good idea - it's the law."

You are missing the point.  It is not about the speed of light, it is  
about the changing rates.  For memory wall, it's about CPU cycle vs.  
DRAM random access latency.  For the presumed content wall, it might  
be long-haul transmission cost vs. storage cost.

> As bandwidth and storage -> infinity, we'll want ways to abuse that  
> bandwidth and storage to get low latency access to content.  If I  
> were making a blatant plug, I'd say that after we get everyone using  
> ECN, we then should get all the app writers to use DOT [1] for their  
> applications.  Scott might say to deploy DONA [2], and Van might say  
> to use his (afaik unnamed) system [3].

Of course, something like that is the broad picture.  I'm trying to  
look a little bit closer.


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