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RE: CIDR Report

  • From: Owen DeLong
  • Date: Sat May 13 18:37:39 2000


> I actually agree with you here as well. relying on infinite router table growth is not a scalable strategy. We need something else.
> 
> 
> 
Just a small technicality here, noone is talking about infinite routing
table growth.  There are only 4 billion (roughly) possible prefixes
if you route every node as a /32.  While 4 billion is a large number,
it is far from infinity.

If you believe the IPv4 will continue for many years to come, then
the set of possible routes is very finite.

Of course, the number for IPv6 is much larger in theory, but when you
consider that the last 6 octets are reserved for the MAC address
(essentially), that leaves 80 bits, which is
1,208,925,819,614,629,174,706,176.  Again, a large number, but,
far from infinity.  When you further consider that on the backbone,
only the first eight octets are at all likely to be significant
for routing, you come to 18,446,744,073,709,551,616 prefixes,
which is still a large number, but even further from infinity.

In my opinion, eventually, we will need to find a way that each
organizational unit is issued a portable, non-renumberable prefix
which stays with that organizational unit.  Some larger
organizational units may need additional prefixes, depending on
the size of the suffix.

Generally, it follows that most strategies for aggregating such
prefixes will tend towards entropy as organizational units change
their topological relationships with other organizational units.

Thus, the only way to preserve aggregation is to make the prefixes
issued to organizational units a function of their topology, and
force renumbering.  While this is a simple matter for topologies
which involve only two organizational units as neighbors, it
becomes n! (n factorial) complex for organizational units which
have n neighbors.  Even with IPv6, I do not believe such a
prefix numbering scheme is practical.

Owen





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