Getting a "portable" /19 or /20

David R. Conrad david.conrad at
Tue Apr 10 20:39:21 UTC 2001


At 03:45 PM 4/10/2001 -0400, Greg Maxwell wrote:
> >       Aggregation buys time, that's it.  Aggregation does not make the
> > current routing methods any more scalable.

No.  Aggregation hides information.  Information hiding promotes 
scalability.  Current routing methods can theoretically be as scalable as 
anyone could ever want if you place well known constraints, namely single 
homing and pure provider based addressing, on entrants into the routing 
system.  Of course, as neither of those constraints are particularly 
appealing to anyone but top-tier service providers and the incremental cost 
of violating those constraints are so small that you quickly get into a 
"tragedy of the commons" scenario.

>In IPv4 yes, because you can't have perfect aggregation, too much network
>multihoming and old prefixes and it's to painful to change address blocks.
>In IPv6, if implimented right aggregation provides for virtually limitless
>scalability for unicast traffic.

IPv6 is not magic.  IPv4 and IPv6 use the same routing paradigm, so if you 
can have virtually limitless scalability with v6, you can have virtually 
limitless scalability with v4.  Problem is:

a) multi-homing is demanded by the market and for multi-homing to make 
sense, you must stop hiding information.  I don't see the market demand 
changing with the deployment of IPv6.

b) CIDR requires renumbering.  If people want to change providers, they 
must renumber into their new provider's block, even with IPv6.  IPv6 is 
supposed to make renumbering easier, however I personally don't believe the 
current addressing model used for IPv6 makes it that much easier than IPv4, 
so there will still be resistance to renumbering in IPv6.


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