Initial Allocation Policy

Background
----------

The advisory council of ARIN asked ARIN to consider changing the current
allcation policy.  The initial allocation to a new LIR/ISP should be
reduced from a /19 to a /20.  The reason being that this would make it
easier for new ARIN customers to receive an allocation directly from
ARIN rather than from their up-stream provider.  According to ARIN's
local allocation policy they would then need to justify the utilisation
of only a /21 instead of a /20 previously allocated to them by their 
upstream provider. 

Another motivation is to improve conservation of address space by
reducing the amount of unused addresses in initial allocations.
The new policy would not increase the load on the global routing,
because the same amount of allocations would still be given out, just
one longer prefix. 

Before deciding on this proposal ARIN has asked the other regional 
registries (APNIC and RIPE NCC) to also consider this change.


Considerations
--------------

Based on the RIPE NCC allocation data starting in 1992 we investigated
how much impact the proposed change would have on the conservation of
address space.  We determined how many LIRs in our service region had
not used more than a /20 from their initial /19 allocation within one
year.  The results are as follows:

Of 1410 LIRs checked 304 (22%) had assigned not more than a /20 during
the first 12 months of operations.  This means that 78% of the LIRs had
used more than a /20 within one year.  The total amount of allocated but,
after one year, not yet assigned address space was equivalent to 19 /16s.
Some of the LIRs which did not have assigned more than a /20 after one
year have since become inactive and the address space concerned will not
be assigned in the foreseeable future.  However 272 of the 304 are still
operational and it is likely that most of them will assign more address
space in the future. 

Further investigations showed that about 50% of those LIRs who haven't
used more than a /20 appear to be multihomed. 


Conclusions
-----------

These results have been presented to the LIR WG at the 31.  RIPE Meeting
in Edinburgh.  The LIR WG is the body defining local address space
policy for the RIPE NCC.  The LIR WG didn't feel that this is a reason
to change the current allocation policy.  The benefits for conservation
are not significant. 

However, the consequences for aggregation are likely to be noticeable 
if 80% of LIRs require a second allocation within a year.
Furthermore the LIR WG expressed concerns about the routability of
longer pefixes in the light of current prefix-length dependent filtering
and flap dampening policies. 

Under the current circumstances the LIR WG did not see a valid reason to
change the current allocation policy. We ask the ARIN membership to
take this into consideration and consider other ways of achieving 
the aims of the proposed change.