[arin-ppml] Rationale for /22

[Owen DeLong]

On Jul 28, 2009, at 10:46 AM, Kevin Kargel wrote:

>> AFAIK, there are no ISPs allowing customers to multihome with less
>> than a /24 currently but many who are allowing those /24s.  So if  
>> that
>> Org gets a /24 from ARIN or a /24 from it's ISP, there is the same 1
>> entry in the table.
>
> This is incorrect.  If the Org gets a /24 from it's upstream ISP  
> there is
> the same entry in the routing table.  If the Org gets a  
> discontiguous /24
> from ARIN there is an additional entry in the routing table.
>
> What it boils down to is whether or not the Org's ISP can aggregate  
> the
> netblock.
>
If an ORG multihomes with a /24 from their ISP, then, that /24 will  
appear
in the routing table either from the second transit provider, or, from
both transit providers, depending on configuration.

If an ORG multihomes with a /24 from ARIN, then, the /24 from ARIN will
appear in the routing table from both transit providers.

Otherwise, there is no difference to the routing table for a  
multihomed /24.
>
>
> But if ARIN is handing out the /24's instead of the ISP isn't the  
> likelihood
> far greater that the /24's will not be agregable?  I doubt that ARIN  
> will be
> able to only hand out /24's that would be.
>
The likelihood of the next /24 being aggregable is low regardless.

>
> I have no problem with extending the minimum mask length so long as  
> it is
> tied hard to a requirement that anyone with a long mask have only one
> allocation, and to get another allocation the long mask netblock  
> must either
> be aggregated in to the new allocation or returned.
>
So how about a policy like:


1.	Amend current policy to extend mutihoming to /24 instead of /22 for  
end users.

2.	Add the following phrase to policy:

	If an organization requesting additional space already possesses one  
or more
	ARIN assignments less than /22, ARIN will, if possible make available  
to the
	organization sufficient space to aggregate existing smaller blocks  
into the new
	space in addition to the justified additional space and shall allow a  
period
	of no less than 18 nor more than 36 months before reclaiming the  
previously
	assigned smaller blocks. If ARIN does not have a sufficiently large  
block, ARIN
	shall issue space in such a way as to alllow maximal aggregation  
possible
	and the return of as many addresses as possible after renumbering.

Owen

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