16 vs 32 bit ASNs [Re: BBC does IPv6 ;) (Was: large multi-site enterprises and PI]

Iljitsch van Beijnum iljitsch at muada.com
Mon Nov 29 10:13:55 UTC 2004


On 29-nov-04, at 7:45, Pekka Savola wrote:

>>> I think it's not. The problem will not go away then, it will just 
>>> take
>>> longer before it appears again. The policies have to get stricter, 
>>> there
>>> is no point in 'fixing' your problems by not fixing the issue that
>>> created them in the first place.

>> Well, how many AS numbers would you like to give out? 30000 in 20 
>> years? 100k a year? A million in a month? 32 bits will then give you 
>> 2863 millennia, 429 centuries or 357 years, respectively.

> Well, as I have said... having to go to 32 bit AS numbers shows that 
> we've failed at ASN policy-making and failed at creating a scalable 
> multihoming solution.

I can see where you're coming from, but I have to disagree. We are now 
more than halfway through the AS number space. If we extrapolate 
current consumption we'll be flat out in 5 to 10 years. That is current 
consumption, which presumably doesn't include any IPv6 multihomers. It 
also doesn't include a significant amount of latent demand, as there 
are lots of PI or PI-like block in the routing table without an AS 
number to go with them. Now reclaiming may put off the inevitable for a 
few years, but what good does this do? We only need one or two years to 
implement 32 bit AS numbers, so spending all this effort and time to 
gain extra time that we don't need (if we start implementing 32 bit AS 
numbers in the not too distant future) is just a waste of resources.

> We don't _want_ to have to give out thousands of AS numbers per month 
> or even a year.  We'd (well, I at least :) would rather that that the 
> endsites had other means to do multihoming which wouldn't require such 
> global resources.

A few thousand AS numbers per year can easily be consumed by new ISPs, 
and new multihoming mechanisms are probably not going to work with IPv4 
or require too many additional addresses to be practical in IPv4, so 
we'll still see AS numbers be consumed by IPv4 multihomers.

> ASN exhaustion is IMHO just a symptom of the real problem.  Enlarging 
> the ASN space does not cure the disease, just makes it worse.

The symptom of the real problem would be _excessive_ AS number 
consumption. My argument is that _normal_ AS number consumption in 
itself warrants the upgrade. And there is nothing wrong with treating 
symptoms, by the way. We really don't want to arrive at a situation 
where it becomes increasingly difficult to obtain an AS number for 
those who legitimately need one.




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