shim6 @ NANOG

Iljitsch van Beijnum iljitsch at
Sat Mar 4 08:21:10 UTC 2006

On 4-mrt-2006, at 3:05, Stephen Sprunk wrote:

>> The alternative, of course, is to wait for IDR to implode and let the
>> finger-pointing begin.

> ... which is what I expect to happen.  A few folks will see it  
> coming, design a fix, and everyone will deploy it overnight when  
> they discover they have no other choice.  Isn't that about what  
> happened with CIDR, in a nutshell?

We got lucky with CIDR because even though all default free routers  
had to be upgraded in a short time, it really wasn't that painful.  
Ok, I wasn't there, but what I mean is that the problem was solved by  
aggregating already deployed address space, which isn't going to fly  
if excessive PI makes IDR implode in the future.

I've been in multi6, two multi6 design teams and shim6 for nearly  
five years, and I've seen many of the smartest people in the IETF  
community join in. I can tell you this: the only scalable solutions  
on the horizon are:

- moving multihoming related state out of the DFZ (this is what shim6  
- remove the requirement that every DFZ router carries every prefix,  
which can't be done as long as PI blocks sit at the top of the  
addressing hierarchy

There are many aspects to current IDR that can stand to be  
improvemed, but at the end of the day that doesn't shrink your FIB by  
orders of magnitude.

The closest thing to a magic, pain-free solution would be to allocate  
PI blocks such that it's possible to aggregate them together and  
ignore the more specifics for far away regions of the world, so that  
in 2030 you don't have to carry 60000 Chinese PI blocks world wide  
that all sit behind the same Great Firewall anyway, but no, that  
doesn't make sense because how can I multihome to ISPs in Shainghai  
and Toronto then, this will never work.

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