Shim6, was: Re: filtering /48 is going to be necessary

Leo Bicknell bicknell at
Tue Mar 13 08:48:05 CDT 2012

In a message written on Tue, Mar 13, 2012 at 02:19:00PM +1100, Geoff Huston wrote:
> On 13/03/2012, at 2:31 AM, Leo Bicknell wrote:
> > It was never clear to me that even if it worked 100% as advertised that
> > it would be cheaper / better in the global sense.
> I think that's asking too much of the IETF Leo - Shim6 went through much the
> same process as most of the IETF work these days: bubble of thought, BOF sanity
> check, requirements work, protocol prototyping, technology specification.

I think you took my statement a bit too literally, as if I wanted
a proof that shim6 would be cheaper than building larger routers.
That would be asking way too much.  However, shim6 for me never
even passed the theoretical smell test economically.

To make routers handle more DFZ routes basically means putting more
memory in routers.  It may be super fancy super expensive fast TCAM
to handle the job, but at the end of the day it's pretty much just
more memory, which means more money.  There's a wild range of
estimates as to how many DFZ routers there are out there, but it
seems like the low end is 50,000 and the high end is 500,000.  A
lot of ram and a lot of money for sure, but as far as we can tell
a tractable problem even with a growth rate much higher than we
have now.

Compare and contrast with shim6, even if you assume it does everything
it was billed to do.  First, it assumes we migrate everyone to IPv6,
because it's not an IPv4 solution.  Second, it assumes we update
well, basically every since device with an IP stack.  I'm guessing
we're north of 5 billion IP devices in the world, and wouldn't be
surprised if the number isn't more like 10 billion.  Third, because
it is a software solution, it will have to be patched/maintained/ported

I'm hard pressed in my head to rationalize how maintaining software for
the next 50 years on a few billion or so boxes is cheaper in the global
sense than adding memory to perhaps half a million routers.

       Leo Bicknell - bicknell at - CCIE 3440
        PGP keys at
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