[ppml] Policy Proposal 2007-6 - Abandoned

John Paul Morrison jmorrison at bogomips.com
Fri Apr 27 15:49:48 EDT 2007

Owen DeLong wrote:
>> Yes, I believe this would lead to a run on IPv4 space
>     Please provide any documentation you can to support this belief.
>     Certainly, the equivalant policy in EVERY other RIR has not 
> created this problems in
>         any other region, so, I'd like to see any data you have that 
> supports this belief.
I don't know how this would lead to a run on IPv4 space, because I have 
had to justify several /24's for
customers - allocated out of Carriers/Telco IP address space to be used 
for BGP multi-homing.
It's a hassle, you are tied to one carrier's address space, and you
have more dependence on the carrier's BGP policies than if you had your 
own /24.
I would prefer to have a direct allocation, but whether I get a /24 from 
a carrier or ARIN, doesn't
really change the address consumption.

The requirement for a /24 to do BGP multi-homing is basically arbitrary, 
but it dates back to concerns
about routing table size. If you could convince the majority of ISPs and 
AS's that /25's  or even longer
prefixes belong in the global routing tables, then you could come up 
with a workable IPv4 multi-homing
solution that doesn't require a /24 allocation. However in practice, 
longer prefixes may not be routable.

Perhaps the wording of 2007-6 should be changed to remove the reference 
to a /24 allocation and focus
on the actual need.  Routing table bloat is a concern, but I'm not sure 
it's as big an issue as it once was 5 or 10 years ago.
If routing table size is really a problem, it's going to be made worse 
with IPv6, since that's going to cause
more growth.  (I'm sure you can have an efficient IPv6+IPv4 RIB in 
backbone routers, but IPv6 will only add routing
entries, and at that point, who cares whether a route is an IPv6 /48 or 
an IPv4 /28?)

If ARIN sets aside some space specifically for multi-homed ASs, which is 
allowed to have /25 or longer allocations, carriers
can still filter the rest of the routing table to restrict more specific 
routes, and can make exceptions for this
address space. But the technical challenges will have to be addressed by 
the carriers and end users, because
prefixes longer than /24 could easily be non-routable.

John Paul Morrison

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