[arin-discuss] Trying to Understand IPV6

[Owen DeLong]

On Sep 13, 2010, at 3:49 PM, Alan Batie wrote:

> On 9/13/10 11:32 AM, michael.dillon at bt.com wrote:
> 
>> Anyone in this position should simply assign a /48 to every customer site
>> no matter how big or small. A one bedroom apartment gets a /48. A
> manufacturing
>> plant with 5 buildings including a 4-story office block, gets a /48.
>> No exceptions.
>> 
>> Later, when you have learned more, you might want to shift to only give
>> a /56 to residential customers if there is a good business reason, but
>> you are more likely to conclude that there is only a reason for large
>> ISPs to introduce this complexity.
> 
> I like to have my cake and eat it to: if you give /48, it's gone.  If
> you give /56, using 1 bits from the left (reserving the first 4 bits: 1
> customer block, 1 us block, 14 in reserve), you have a sparse allocation
> that, if the customer needs /48, you can easily expand them into by
> shrinking the netmask.  Eventually the bits from the left will run into
> the bits from the right, but by that time, we'll have a lot more
> experience with the subject.  If we need more /56's, we'll have them. Up
> until that point, if people turn out to need /48's (or more!), no problem.
> 
This is a really horrible approach... Yes, if you give a /48, it's gone.
So what?

If you need more /48s, then, get another /32 or even a shorter than /32
prefix.

Really... There's plenty of space to do this for quite a while and still not
even use 0.2% of the first 1/8th of the IPv6 address space.

For sparse allocation, allocate your /48s by bisection...

Customers (in order of allocation):

Internal:	XXXX:XXXX:0000::/48
First:		XXXX:XXXX:8000::/48
Second:		XXXX:XXXX:4000::/48
Third:		XXXX:XXXX:C000::/48
Fourth:		XXXX:XXXX:2000::/48
Fifth:		XXXX:XXXX:6000::/48
Sixth:		XXXX:XXXX:A000::/48
Seventh:	XXXX:XXXX:E000::/48
Eighth:		XXXX:XXXX:1000::/48
Ninth:		XXXX:XXXX:3000::/48
...
Fifteenth:	XXXX:XXXX:f000::/48
16th:		XXXX:XXXX:0800::/48
17th:		XXXX:XXXX:1800::/48
...
31st:		XXXX:XXXX:f800::/48
32nd:		XXXX:XXXX:0400::/48
33rd:		XXXX:XXXX:0C00::/48
34th:		XXXX:XXXX:1400::/48
35th:		XXXX:XXXX:1C00::/48
...
63rd:		XXXX:XXXX:fC00::/48
64th:		XXXX:XXXX:0200::/48
65th:		XXXX:XXXX:0600::/48
...
	

As you can see, you get lots and lots and lots of customers installed
before they get packed with any level of density. Specifically, you
get 255 customers installed before you have to put any of them
close enough that they can't all be expanded to 256 /48s (a /40).
You get 4095 customers installed before you have to worry
about any of them not being able to expand to a /44.

You can have your cake and eat it too without complicating your network as you describe.

Owen


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.arin.net/pipermail/arin-discuss/attachments/20100913/cf83c9c4/attachment.html>