[ipv6-wg] 96 more bits... time for some magic after all?

On Fri, Oct 25, 2013 at 5:24 PM, Benedikt Stockebrand
<bs at stepladder-it.com> wrote:
> Hi Shane and list,
>
> Shane Kerr <shane at time-travellers.org> writes:
>
>> All,
>>
>> [ gah... hit the wrong key and sent this unfinished ]
>>
>> We saw two presentations by network architects at the RIPE meeting that
>> used bits in their IPv6 addressing plan to carry meaning beyond simple
>> network topology and packet routing.
>> [...]
>> This includes the long-standing historical goals of conservation,
>> aggregation, and accuracy.
>>
>> Using bits in IPv6 networks for other purposes is orthogonal to those
>> goals.
>>
>> What should we do about it?
>
> as long as they don't need more than "their share" of the address space
> as defined by the policy applied to everyone: Nothing.
>
> More important however is the question how to deal with them if /when
> they show up because they have unnecessarily "depleted" their address
> assignment thanks to encoding stuff in it.  I strongly suggest to send
> them home to renumber their network (and hope it hurts enough to teach
> them and everyone watching a lesson).
>
> It's not much different than with IPv4.

It is just bits, numbers, never forget that.

How people/ISP/something chose to use what is available to them really is
upto them. We have some experience since we started to use IPv6 back in
the 90s, and we also have some guidelines on what is a good idea, and
what is a really horrible idea.

What is a bad idea, so far almost all agree somehow, is to put too much
semantic into the IPv6 address. Some is great, and usefull, but chose
wisely. Only difference from IPv4 is the amount of space you can _misuse_.


It's upto each and every operator do make the chose _they_ think is the
right for themself. If they ignore the advices given and run out, renumber.

If they run out due to size and growth, and they haven't wasted space,
used their available /29 wisely by every advice given...give them
another prefix.



> Beyond that, there are some more aspects to consider:
>
> - Work the numbers.  With IPv4 addresses and 32 bits we have kind of
>   managed to come to grips at an intuitive level.  With IPv6, this
>   simply doesn't work anymore; a /29 for Deutsche Telekom is
>   ok. However, if they start to code more stuff into the addresses, this
>   will quickly break down.  In other words: No matter what, 128 bits are
>   still just 16 bytes.  If other people follow suit and start to encode
>   things in their addresses, we may run out of space *very* quickly.

I did some calculation long time ago, 2002-2003 or around there, only
thing I remember is that IPv6 isn't really that huge, it's big and plenty for
sure but if we start to waste we will run out quite fast. Very fast.
One way to waste is to give every single customer a /48 when you are
really really big. /56 work just fine really, even for techies like me :)


However IPv6 is big enough that most people will not feel any pain with
it, some however will start to get into trouble in 5-10years time, guess
more like around in 7 years. The reason? They made a too static model
on how they wanted to use their available space. But you have to be
big to get into that trouble.


> - Remember that they effectively nicked the extra five(?) bits from the
>   subnet ID, by handing out /56s instead of /48s as originally
>   intended.  They can only do that so often.

There was major discussion just to get that /56 into the documents.
Upto that point there was /64 pr.LAN, /48 for the rest. Now we're relaxing
it even more. Are discussion on moving away from /64's on the wire to...

Doesn't this sound like A/B/C-class network vs CIDR?




>From my own experience over the years, since early days in 97 upto
now, there isn't a one size fits all as I too believed in the early
days of IPv6.

* For one server running in the cloud I got a /112, that work just fine really.
* Somewhere else I'm using a /50 on the wire, that also work just fine.
* I have tried to use an entire /48 but failed. I tried to build my
own network with VPN, routings and everything across the different
servers and routers I have spread around. That /48 was big enough for
me:)
* I tried to build a big routed, multisite network using a /56, that
also worked upto a certain size :)



-- 

Roger Jorgensen           | ROJO9-RIPE
rogerj at gmail.com          | - IPv6 is The Key!
http://www.jorgensen.no   | roger at jorgensen.no