Shim6 vs PI addressing

Stephen Sprunk stephen at
Fri Mar 3 17:53:44 UTC 2006

Thus spake "Todd Vierling" <tv at>
> On Wed, 1 Mar 2006, Iljitsch van Beijnum wrote:
>> 3. Route processing and FIB lookups scale worse than linear
>> 6. Moore can't go on forever, there are physical limitations
> The funny part:  Those on this list who have cited Moore's Law don't
> seem to have an understanding that it does not directly apply to
> custom routing logic (since general-purpose CPUs are no longer fast
> enough to do the lookups on the high end).  In addition, GP CPUs
> are no longer scaling exponentially, but rather closer to quadratically
> and approaching linear.
> In short, Moore's Law is dying,

Moore's Law says nothing about performance; it only refers to transistor 
densities.  In fact, current CPUs are still following the predicted curve, 
but they're turning fewer and fewer of those transistors into actual 
performance improvements.  That's what the move to dual-core is about: 
finding more productive ways to use the wealth transistors now available.

However, I agree that custom logic for routers does not necessarily follow 
the same curve; the volume is still low enough that vendors can't (or don't) 
use the best processes available.  Heck, even the best available main CPUs 
are several years behind what's available in the PC market (why ship a 2GHz 
CPU when you can ship a 500MHz one at ten times the price?).

> and even if it weren't, it is not a valid argument for "let the swamp in".

One of the key attributes of the v4 swamp is that most orgs got more than 
one assignment (aka routing slot), often dozens to hundreds; the proposed 
policies for a "v6 swamp" do not allow that.


Stephen Sprunk        "Stupid people surround themselves with smart
CCIE #3723           people.  Smart people surround themselves with
K5SSS         smart people who disagree with them."  --Aaron Sorkin 

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