Biggest mistake for IPv6: It's not backwards compatible, developers admit

S.P.Zeidler spz at
Wed Apr 1 06:58:03 CEST 2009


Thus wrote Leo Vegoda (leo.vegoda at

> On 31/03/2009 10:00, "S.P.Zeidler" <spz at> wrote:
> [...]
> > Traditionally, in the RIPE region (not counting historical PI from before
> > PA was invented), the way to get PI space in v4 is to get an AS first
> > (or mostly, to get an AS and the PI space to route with it as a bundle).
> I recall networks qualifying for exactly as much IPv4 PI space as they would
> qualify for PA space without a multi-homing requirement. So very small
> networks might well only get a /29 of PI space.
> This high granularity of PI assignments was a possibly a disincentive to an
> excessive number of requests. Or it might have encouraged people to inflate
> the interface count to something more than 128, ensuring a /24 assignment.

Even back when I was an active LIR hostmaster (1998-2001 roughly) it was
more theoretically possible than practical to get PI without the reason
'multihoming' being in evidence. I somehow doubt that changed into the
direction of easier availability :) And I distinctly remember a case with
a PI request where the 3 year plans would have been covered by a /25, but
the argument of routability yielded the customer a /24 (after some
extended complaining at the responsible hostmaster @RIPE, granted).

> In any case, it looks like the number of PI assignments exceeded the number
> of PA allocations back in 2003:
> (slide 9)

If that really is all the requestor will need, it does save address space.

> I note that RIPE policy proposal 2006-05 would set the minimum assignment
> size to /24 in some multi-homing cases. On the other hand, things seem to be
> changing in a way that assigns a higher ongoing cost to PI assignments,
> which might balance out the equation somewhat.

It would certainly remove the "pay once, own forever" lure of PI space over
a PA allocation that currently is in effect.

spz at (S.P.Zeidler)

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