Address clustering intuition

Geert Jan de Groot GeertJan.deGroot at
Thu Nov 9 22:22:20 UTC 1995

On Thu, 09 Nov 1995 10:16:39 -0700  "Walter O. Haas" wrote:
> I've formed an intuition that, if all IP addresses were portable (ie.
> independent of ISP) and assigned on a strictly geographic basis, then
> there would *automatically* be clustering of addresses equivalent to
> that obtained from CIDRization as a result of marketplace forces and
> the practicalities of technology.

No, this does not work. Looking at Europe, I know of several ISPs
to which the shortest path from here (Amsterdam, the Netherlands)
is via MAE-EAST; they either don't have external connectivity
on the continent itself, or we have no provider willing to provide
transit between here and their continental connectivity.

There is a second, similar reason: assume that A and B each operate
in the same area. They use different carriers for transit to MAE-EAST.
Who of these is going to announce the aggregated announcement?
If A does it, it pays for the transit for customers of B.
If they both announce it, then they still pay for eachother's


Geert Jan

PS: it seems that a FAQ on this is desired (CIDRisation, router capacity 
growth vs routing table growth, flaps, need to renumber, etc), basically
the topic of various discussions on NANOG, CIDRD, and probably
other places. Volunteers?

> Note that this results from the address being, not the property of the
> ISP or the end user, but rather of a geographic location.  In other words
> under my scheme if I picked up and moved a hundred miles I'd have to
> renumber, but if I just switched ISPs I wouldn't.
> -- Walt

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