[arin-ppml] IPv6 Allocation Planning

michael.dillon at bt.com michael.dillon at bt.com
Thu Aug 12 05:40:57 EDT 2010

> I was simplifying a bit.  About a third of our customers are dynamic
> 802.11 hotspot customers.  Since those are each single hosts,

You've got to be joking. Have you never heard of tethering? This is
where one device with a wireless connection, allows a second device
to transport traffic over that connection. I did it back in 2000
with a Nokia mobile phone tethered to a Palm V over infrared to run
a web browser and check my email at yahoo.com. Nowadays it is more
often a 3G cellphone tethered via wifi to a netbook or iPad, but
there are many variations, some of which involve so-called mifi
where a wifi device acts as a router for a bunch of other

That means that many of your customers have 2 hosts and some
of them have entire subnets connected. On IPv6 you should not
give a wifi customer less than a /64, and it may even make sense
to assign a /56 given the march of miniaturization and device

> I can't
> foresee allocating  more than a /64 per hotspot 

Even if you assign /64s to the customers on the hotspot, it still
makes sense to allocate a /48 to the hotspot.

Here is a rule of thumb. Write up your IPv6 addressing plan.
Now look at each level of the aggregation hierarchy and ask
yourself, "am I being wasteful?". If the answer is no, then
you got it wrong and should increase the allocation size at 
that layer and probably all layers above it.

If you don't do that you are just shooting yourself in the foot
and will need to redo your network architecture in 3 years
while your competitors are laughing at you because they understood
the fundamental ACCORDION principle of IPv6 addressing. You have to
be able to expand each level in the hierarchy without affecting
higher or lower levels in the hierarchy.

For instance, a customer signs up for Internet access for their
laptop at home. You assign them a /48. You never hear from
them again except to buy bigger bandwidth every do often
and one day you are driving by and see that this
customer now has a medical clinic with 10 people working
there and a special radiology clinic with a scanner that
sends multi gigabyte scans to the local hospital several
times a day. You walk in and there are network connected
devices everywhere. The TV in the waiting room is showing 
Hulu programs, the phones are all Cisco VoIP devices,
the medical personnel are all carrying iPadv7 tablets
and there are three closets full of cables and server racks
which the chief doctor uses to serve up his lectures 
via the Open University on the Internet. And that /48
allocation still has space to spare.

That is what IPv6 addressing is meant to bring us.

--Michael Dillon

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