Renumbering for better aggregation (was Re: too many routes)

J.D. Falk jdfalk at
Tue Sep 9 23:04:23 UTC 1997

On Sep 9, Phil Howard <phil at> wrote: 

> One of the effect of a downstream provider renumbering to aggregate
> IP space, is that they will be handing space back upstream.  That's
> fragmented space and now it makes the upstream provider _look_ less
> efficient because they have to still go get /19's or larger from the
> NIC, but now have all these small holes.

	That's a good theory, those small holes could
	eventually add up to bigger blocks, and the process would
	continue using recycled instead of newly allocated space,
	but that won't always be able to happen.

> We need to make sure the upstream provider is given an incentive to
> get the downstream provider to aggregate.

	You get into sticky territory there.  *grin*

> Implement the ability to do filtering based on the total number of routes
> of a given size per ASN.  The way this would work is that an array of small
> 8 bit (mayber smaller) numbers would be kept per ASN.  There would be 8
> numbers corresponding to network sizes /17 to /24.  When a new route of a
> given size comes in, it's corresponding size number is incremented.  If the
> total for that size in that ASN exceeds a maximum value configured for that
> size, then the new route is filtered out.
 [ . . . ]
> I just came up with this idea, so it hasn't been refined.  Do shoot it down
> if it deserves to be shot down, but realize that any flaws haven't had a
> chance yet to be resolved, and that maybe this could work if fine tuned.

	Interesting idea...not sure if it would be adoped by a large
	group of providers, but interesting nonetheless.

> > 	My guess would be that it'd be a little more difficult if
> > 	you or your customer were trying to reaggregate without the
> > 	impetus that your existing addresses didn't have valid 
> > 	reverse DNS any more, and were gonna be forcibly reclaimed
> > 	in a few months.
> You cut things off like DNS, and the customer, having to renumber anyway,
> will renumber to another ISP.  

	That wasn't us (the company I worked for at the time) who cut
	off the reverse DNS -- that was AGIS.  Check the NANOG archives 
	for posts regarding how I felt about that at the time.

J.D. Falk                         voice: +1-415-482-2840 	
Supervisor, Network Operations      fax: +1-415-482-2844

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