[ppml] /48 vs /32 micro allocations

Kevin Loch kloch at hotnic.net
Mon Mar 14 21:54:43 EST 2005

bmanning at vacation.karoshi.com wrote:

 > On Mon, Mar 14, 2005 at 07:08:38PM -0500, Kevin Loch wrote:
 >> Is there any benefit at all to allocating a /48 to name servers and
 >> exchange points instead of a /32?
 >     yes.

For example?

 >> There is no shortage of /32's, with 536 million of them in 2000::/3.
 >     it does -seem- pretty large, doesn't it?

I would argue that it is too large.  Do you really want
67 million possible routes?  Keep in mind that this
is for "Aggregatable Global Unicast Address Format".
It's very likely that if we relly did want 67 millions routes
we would be using a different address format outside of 2000::/3
since 67 million does not seem congruent with "Aggregatable".

 >     ISPs are free to filter on any boundar(y/ies) that they
 >     see fit to.  Many (most?) filter on published RIR allocation
 >     boundaries, some based on IETF recommendations, and SOME
 >     based on customer demand.

I agree but In IPv6 right now most appear to be filtering /49 and 
longer.  Is the micro allocation policy having an affect on this?
This is not about how you or I filter on our own network, it's about
the de-facto minimums that result from RIR policy, intentional
or not.

 >> RIR filter suggestions do not seem to matter, but allocation
 >> sizes do.
 >     Sort of.  No RIR delegation is explicitly routable. Routability
 >     is not an attribute of RIR delegations.  Routability is up to
 >     the respective ISP's.

And most ISP's eventually filter to the lowest common denominator,
and that determines the de-facto MRU.  RIR delegations have a
substantial effect on that.

 >> Market forces, technology limitations and end site assignment sizes are
 >> also factors but there is a real risk that RIR allocations will result
 >> in a smaller MRU than these factors otherwise would.  I'm not saying
 >> that using /32's for special allocations will prevent a /48 MRU, but it
 >> is irresponsible to ignore the effects that these /48 allocations may
 >> have.
 >     There are other effects associated w/ large delegations that
 >     remain sparsely populated.

Are there any allocations in IPv6 that will not be sparseley populated?
Even in bits 0-48 I would argue that most will remain sparsely
populated.  Only 56% of IPv6 allocations are even announced right now.

 >> So, to be on the safe and responsible side, should ARIN set a minimum
 >> allocation size of /32 for *any* direct allocation regardless of type?
 >     That would be bad - on many different levels.

Please explain.  Even if consensus is that this is a bad idea we should
have the reasons clearly stated.

Kevin Loch

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