[143331] in North American Network Operators' Group
Re: IPv6 end user addressing
daemon@ATHENA.MIT.EDU (Owen DeLong)
Sat Aug 6 12:51:19 2011
From: Owen DeLong <owen@delong.com>
In-Reply-To: <CAHDzDLDLcSAQR5fmNeStFsqt1DttCrAhY7WtVxP57nt0t5DmHg@mail.gmail.com>
Date: Sat, 6 Aug 2011 09:48:55 -0700
To: Mukom Akong Tamon <mukom.tamon@gmail.com>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
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On Aug 6, 2011, at 3:40 AM, Mukom Akong Tamon wrote:
> On Fri, Aug 5, 2011 at 11:18 PM, Doug Barton <dougb@dougbarton.us> =
wrote:
>> For example, if you reserve a /48 per customer but actually use the
>> first /56 out of it, you are safe if _you_ need the other /56 for =
some
>> reason, or if the customer needs to expand into the full /48.
>=20
> +1. Be generous in planning and then assign what makes operational
> sense. Be sure to make sure that as you dole out smaller than blocks
> to customers that requested from your RIR, you preserve your ability
> to give a client a second block from the same aggregatable range.
>=20
The way to address this better is to use allocation by bisection to your
customers rather than giving them /56s.
If you give a site a /48, it is very unlikely they will ever need an =
additional
prefix for that site. Of course if you're talking about a customer that =
is
using a single connection to you to feed multiple sites, that's a =
different
issue and will require additional planning.
For anyone that already understands allocation by bisection, you can
skip the rest of this message.
What I mean by allocation by bisection is simply issuing prefixes such
that each issued prefix has the largest possible contiguous aligned
space available for expansion. Let's assume 2001:db8::/32 as our
starting point and that we are assigning /48s to 50 end sites from it.
(I'm skipping the whole hierarchy to fit inside a /32 and keep the =
example
simple).
We'd assign 2001:db8::/48 for our own infrastructure and support =
machines.
The first customer would get 2001:db8:8000::/48.
The next customer would get 2001:db8:4000::/48, then 2001:db8:c000::/48.
In the next round, we'd assign 2001:db8:2000::/48, 2001:db8:6000::/48,
2001:db8:a000::/48 and 2001:db8:e000::/48
This would be followed by =851000::/48, =853000::/48, =855000::/48, =
=857000::/48,
=859000::/48, =85b000::/48, =85d000::/48, and =85f000::/48.
At this point, we've assigned 15 customers, and each of them could be
expanded from /48 to /36 without invading any of our existing =
assignments.
Continuing, we would assign the next 16 customers as:
2001:db8:0800::/48, 2001:db8:1800::/48, 2001:db8:2800::/48,
2001:db8:3800::/48, 2001:db8:4800::/48, 2001:db8:5800::/48,
2001:db8:6800::/48, 2001:db8:7800::/48, 2001:db8:8800::/48,
2001:db8:9800::/48, 2001:db8:a800::/48, 2001:db8:b800::/48,
2001:db8:c800::/48, 2001:db8:d800::/48, 2001:dbu:e800::/48,
2001:db8:f800::/48
That brings us to 31 customers all of whom have room to expand
their /48 up to a /37 (though I wouldn't recommend doing /37s
as they are not nibble-aligned, so, outside of exceptional =
circumstances,
you would be unlikely to expand in place beyond /40 at this point.)
The next 32 customers would fill in the 2001:db8:?400::/48 ranges
and the 2001:db8:?c00::/48 ranges. This limits those customers
now to /38s.
Owen
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