[arin-ppml] Rationale for /22

Owen DeLong owen at delong.com
Fri Jul 31 14:59:19 EDT 2009

On Jul 30, 2009, at 5:10 PM, Michael K. Smith wrote:

> On 7/30/09 4:05 PM, "Owen DeLong" <owen at delong.com> wrote:
>> On Jul 30, 2009, at 3:46 PM, Leo Bicknell wrote:
>>> In a message written on Thu, Jul 30, 2009 at 05:48:06PM -0400,  
>>> William Herrin
>>> wrote:
>>>> If I may draw it back to the question I started with: Can you  
>>>> offer a
>>>> well grounded reason to believe that changing the minimum  
>>>> allocation
>>>> size for *multihomed* systems is likely to affect the size of the
>>>> global table?
>>> I believe it is reasonable to assume each decrease in prefix size
>>> allows more orgs to qualify, and thus increases the routing table.
>>> Now it may be we only add 1000 orgs, of which 800 previously were
>>> multi-homing with cutouts, so the net is 200 routes, but that  
>>> doesn't
>>> mean it's not a decrease.
>> I don't get this...
>> Under current policy, any org that multihomes qualifies for a /24  
>> from their
>> upstream.
>> Given that, any org that multihomes already qualifies to put a  
>> route in the
>> DFZ.
>> What increase are you concerned about that is added by moving the  
>> boundary from /22 to /24?
>> Today, they can save $100/year and get space from an upstream that
>> they don't pay ARIN for, as well as getting a  /24 even if they  
>> want to
>> multihome a single host.  That's CURRENT ARIN policy.
>> If we move the boundary to /24, then, in addition to that option,  
>> networks
>> that have ~128 - ~400 hosts would gain the option of applying to ARIN
>> and getting a /24 or /23 to multihome with that was independent of
>> both of their providers.
>> Why would someone who is not willing to multihome for $100 less
>> pay $100 more to multihome _AND_ jump through more hoops just
>> because we changed the ARIN boundary?
>> Owen
> Are you saying you think that a small provider with a upstream- 
> provided /24
> wouldn't want to jump through the hoops to be provider independent?   
> In the
> past, I've been in just this type of position, advertising multiple / 
> 24's
> assigned from upstreams until I could justify a /20 from ARIN.  If I  
> had the
> opportunity to number out of a /24 instead of waiting until I had a / 
> 22 I
> would have jumped at the chance.
I'm saying that said same entity would not increase the routing table by
getting their space from ARIN.

Nobody who wants to multihome is avoiding doing so because they can't
get space from ARIN.

> What was the rationale for the /20 in the first place?  Was it more  
> than an
> arbitrary number?  I can't see any detraction from getting providers  
> to get
> an ARIN-assigned /24 instead of having to get a /24 from one  
> provider and
> route it out another, being historically on the "purchasing" side of  
> that
> arrangement.  The only downside I can see is providers that think  
> having a
> customer with their assigned space somehow binds them together,  
> fiscally
> speaking.
Exactly.  I'm disagreeing with Leo's assertion that allowing ARIN to  
longer prefixes would somehow increase the routing table.


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