North American Network Operators Group

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

  • From: Michael.Dillon
  • Date: Tue Nov 30 07:23:32 2004

> Of course, every ASN would not be active.  But if we'd have 32 bit 
> ASNs, there would be "no need" (or so folks would argue) to be strict 
> in the policies -- everyone and their uncle could have one.  Folks 
> could even get ones for their homes, theis SOHO deployments, or their 
> 3-person, on-the-side consulting companies.  And logically, each of 
> these should have their own PI prefixes and a slot in the global 
> routing table.
> Scalable? NO.  Not just the number of routes, but also the churn those 
> routes would make.. Oh god.

This is where a sensible geographical addressing hierarchy
comes in. Start by allocating a very big chunk of the v6
address space to geographical addresses. This chunk should
be approximately the same size as the chunk that we expect
to use with the current allocation system. We can easily
afford to block off this much space in v6.

Now, subdivide this chunk into 6 geographic blocks. 5 of
those blocks will go to the 5 existing RIRs including
Afrinic. The 6th will go in reserve to be subdivided in
smaller pieces to places that don't fit the RIR system.
Antarctica, ships at sea, airplanes, space stations. 
There is no guarantee that we would need any of this
6th block, but better safe than sorry.

Now, within its geographic block, each RIR would need
to develop some plan for subdividing its region into
geographic areas that roughly follow the trade and
fiber flows of the region. The subdivision is rough
because it is not the boundaries that matter, it is
the exchange points. Geographic addresses will not
work without exchange points. The allocation scheme
will be to give addresses to echange point areas
in such a way that all addresses within an area
can be aggregated outside the area.

This way, the global routing tables see only 5 or
6 routes for the entire geographic space. Of course
some larger providers with lots of intercontinental
connectivity will see a larger number of routes to
the different areas within a region. But only local
providers and exchange points need to see the full
detail of any particular area.

This provides a way for smaller organizations to
get provider independent blocks of IPv6 addresses
so that they can change providers within their
geographic area without renumbering. It doesn't
solve every problem of renumbering, but it does
provide a way for a very large number of smaller
organizations to enjoy the same advantages of
the larger companies without dirtying the pool
in which the larger companies play.

This is scalable. It introduces hierarchy in two
ways. One, the geographic addresses form a separate
routing topology from the flat mesh that most on
this list seem to want. This makes the flat mesh
more scalable. Secondly, the geographic addresses
form a topological hierarchy internally which allows
that topology to scale much bigger than the flat 

This is fundamentally an operational solution.
No protocol changes are needed, the IETF doesn't
need to do a thing. This plan would not work unless
the RIRs plan and enforce the geographical hierarchy.
On the other hand, this is well within the capabilities
of the RIRs (and the NRO) to implement.

--Michael Dillon