[sclug] Who needs a /48?

[Paul Lettington]

On Wed, Apr 10 2013 14:27:56 +0000, Ed Davies wrote:
> On 2013-04-07 19:47, Keith Edmunds wrote:
> > Well, if you choose to use BT as your ISP... Seriously, I wouldn't. In my
> > experience, the smaller ISPs are way, way better. I'm now with Andrews and
> > Arnold, and would recommend them (they're not as expensive as I thought
> > they would be, and they are good).
> 
> Interesting. I see that A&A offer /48 addresses. Space is big, etc,
> but still this seems a bit wasteful. We've, in effect, run out of
> IPv4 /32 addresses. 65536 (minus a few) times is a lot more but there
> are a lot of bods on the planet, too.

<delurk/>

I work for A&A, and yes, we allocate /48s per customer. The customer may
well have multiple lines or hosted servers etc, and can choose to route
smaller blocks from that /48 to their lines as they see fit. By default
we route a single /64 to each ADSL line.

We have 2001:8b0::/32, and the following seven /32s after that are
reserved for our use when we need them, which effectively gives us
2001:8b0::/29. That will let us give /48s to 500,000+ customers before
this becomes a problem.

> By the time you've dropped a few bits off the front for different
> addressing schemes that only leave a few hundred addresses for each
> of the 10 billion or so people likely at peak peeps - a small enough
> number that some sort of careful management would be required.

I have to question the maths here. How many bits are you dropping off
the front, and what for? There are 2^^48 /48s in the 128 bit IPv6
address space. Given your peak population of 10 billion, that's 28,000
/48s for every individual's personal use, and each /48 contains a
trillion trillion addresses.

Even a single /48 used for the whole world's address space is enough to
give these 10 billion people over 120 trillion addresses each.

> I can just about see the argument for a /80 address. It allows you
> 32 bits to route any existing IPv4 addresses you are using plus
> another 16 bits to fence those off and route anything IPv6 you have.
> Why would anybody want any more?

I don't know. I can't think of a use for more, but since the address
space is so big, is there any need to worry about it?

> Any advance on that?

It's worth noting that IPv6 allocations are currently only happening
from 2000::/3 which is 1/8th of the possible address space. If the world
chews through that significantly faster than expected, the plan is to
re-think the address allocation policy before moving on to the next
1/8th.

-- 
Paul.