[arin-ppml] ARIN-prop-127: Shared Transition Space for IPv4 Address Extension

[Matthew Kaufman]

On 1/20/2011 11:42 AM, William Herrin wrote:
>
> Setting aside one
> space that every ISP can use seems like a smarter solution than each
> ISP carving out a piece of their otherwise publicly routable space for
> the task.

Why?

And I'll note that if *any* ISP carves out a piece of their space for 
this, *any other* ISP can reuse exactly the same space.

In fact, a bunch of ISPs could get together and simply apply for space 
now, or out of the transition-reserved pool, or buy it through the 
transfer market for this purpose.

>
>
> I just programmed 10.0.0.0/8, 172.16,0.0/12 and 192.168.0.0/16 on my
> network. My ISPs are now conclusively shown to have a conflict with my
> active and valid internal addressing.
>
> Seriously Wes, that's not a sound argument. There are only 70,000
> /24's in RFC1918 space and folks who don't take their home routers'
> default often select much more than a /24. Of _course_ any ISP of
> non-trivial size is going to conflict with some of his customers if
> they're both selecting from the same relatively small pool.

As far as I can tell, if you don't care about your customers always 
being able to talk to each other the collision space is only against a 
single /30, not a whole /24, of RFC1918 space, if you're doing it right.

And if your customers do want to talk to each other, you can make that 
work with much less than a /24 worth of collision space as well, though 
some customers who make certain internal address assignment and routing 
decisions will be unable to reach others.


>
> This is a red herring. Customers who deliberately break their networks
> are in a whole different category than the ones where I've
> inadvertently stomped on their reasonable and legitimate
> configuration.
>

Well, once my ISP starts assigning out of, say, 10.0.0.0/8, it might not 
be "reasonable and legitimate" for my customers to expect that using 
10.0.0.0/8 indiscriminately internally any more.

Transition is going to be painful and require changes. This is, in some 
cases, one of those changes.

Matthew Kaufman