estimation of number of DFZ IPv4 routes at peak in the future

William Herrin bill at
Sat Mar 12 07:00:10 CST 2011

On Sat, Mar 12, 2011 at 2:17 AM, Joel Jaeggli <joelja at> wrote:
> I'm super-tired of the "but tcams are an expensive
>non-commodity part not subject to economies of scale". this
>has been repeated ad nauseam since the raws workshop if not before.
> You don't have to build a lookup engine around a tcam and in fact
>you can use less power doing so even though you need more
>silicon to achieve increased parallelism.

Hi Joel,

You're either building a bunch of big TCAMs or a radix trie engine
with sufficient parallelism to get the same aggregate lookup rate. If
there's a materially different 3rd way to build a FIB, one that works
at least as well, feel free to educate me. And while RIB churn doesn't
grow in lockstep with table size, it does grow.

Either way when you boost from 1M to 10M you're talking about
engineering challenges with heat dissipation and operating challenges
with power consumption, not to mention more transistors. I'll be
convinced it can be done for less than 2x cost when someone actually
does it for less than 2x cost.

Whether it's 2x cost or 1.2x cost, the point remains the same: we
could have routers today that handle the terminal size of the IPv4
table without breaking the bank.

Your favorite router manufacturer has made vague assertions about how
they would build one given sufficient customer demand. So make a

Bill Herrin

William D. Herrin ................ herrin at  bill at
3005 Crane Dr. ...................... Web: <>
Falls Church, VA 22042-3004

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