IPv6 - real vs theoretical problems

Tony Hain alh-ietf at tndh.net
Mon Jan 10 16:02:14 CST 2011

*requested anonymous* wrote:
> (I don't post on public mailing lists, so, please consider this
> private.
> That is, I don't care if the question/reply are public, just, not the
> source.)
> On 1/10/11 11:46 AM, Tony Hain wrote:
> > ... yes I know you understand operational issues.
> >
> > While managed networks can 'reverse the damage', there is no way to
> fix that
> > for consumer unmanaged networks. Whatever gets deployed now, that is
> what
> > the routers will be built to deal with, and it will be virtually
> impossible
> > to change it due to the 'installed base' and lack of knowledgeable
> > management.
> >
> > It is hard enough getting the product teams to accept that it is
> possible to
> > build a self-configuring home network without having that be crippled
> by
> > braindead conservation. The worst possible value I can see for
> delegation to
> > the home is /56, yet that is the most popular value because people
> have
>   ^^^^^^^^^^^^^^^^^
> Why would you say /56 is the worst possible value?  Just curious --

I am actually trying to develop a simple set of 'auto conf' rules for all the CPE vendors to build against, and for a Joe-sixpack plug-n-play network configuration a /56 means there is only one topology option beyond single subnet. 

> my provider doesn't offer IPv6 yet, but, I think they will soon.
> I was going to ask for a /56 for my home net.  If I ever get around
> to using them to set up a domain for my wife's business, I will ask
> for a /48, but, for a house without a private domain, /56 seems
> perfect.

You are thinking of a managed network. Connect a random graph of boxes, then figure out a subnet scheme that all cpe vendors can implement that will correctly deal with prefix delegation and hierarchical routing. 

> I don't expect to run out in my lifetime, or even my children's
> or grandchildren's lifetimes if somehow the house stays in the family
> ;-)
> How many subnets will they really need, no matter if every lightbulb
> is on the net?

Wrong question. In a managed network that would be the right question, but in an unmanaged one the right question is how many sub-delegations and how many branches per sub-delegate are going to be automatically figured out. 

> My frame of reference is that while we need to make the addresses big
> enough, we also need to preserve the hierarchy.  There is no shortage
> of addresses, nor will there be, ever, but there could be a shortage
> of levels in the hierarchy. I assume you would like a home to have a
> /48?  But, from my provider's /32, that is only 4 levels at the
> assumed nibble boundary.  I think my provider could use another
> two levels.

If your provide has more than 10,000 customers they should never have gotten a /32. The braindead notion that everyone needed to rush out and get a /32 has not helped get IPv6 deployed. The /32 value was the default one for a startup provider. Every provider with a customer base should have done a plan for a /48 per customer, then gotten the right size block to start with. Any provider with a /32 and more than 10k customers needs to do that now and swap for 'a real block', instead of trying to squeeze their customers into a tiny block due to their insufficient initial request. 

> I also think ~256 subnets has stood the test of time -- seldom in
> the last 25 years has a geographically contiguous enterprise network
> (such as a university or company) required more than 256 subnets --
> except for cisco, microsoft, et al., but not, e.g. most colleges,
> universities, research centers, etc.  More addresses, sure, but,
> not usually more than 256 subnets.  So, even in a world where
> every possible device has its own set of addresses -- how many
> subnets will I really need?

Again, wrong question. Most of the possible subnets in a Joe-sixpack configuration will be 'wasted'. So what? That space will be wasted sitting on the shelf at IANA in 500 years when someone comes up with a better idea. IPv6 is not the last protocol known to mankind (unless the 2012 predictions are true), so most of its potential space will be wasted. Get over that point and accept that innovation requires thinking differently than the limited myopia of the past.

> Also from my frame of reference -- we need to work on making addressing
> and re-addressing easier and more automatic for consumers anyway, so,
> if /56 is not enough, we can easily and painlessly switch to a /52
> with no problems.  

Easy in a managed network where it is possible to update code and expect that things will happen in a timeframe that makes development worth the effort. Impossible in consumer land where it is well documented that things are never updated, and all vendors need to play by the same simple rules because there is no hope that the consumer will know how to tweak them.

> And, if I decide to grow an enterprise from home,
> I feel that I should be able to re-address as needed over the course
> of time anyway, so, I would rather make re-addressing easier than
> put all my eggs in the large-enough-/48 basket.  What if I grow so
> large that I buy someone else's company, or otherwise merge?  We have
> to solve the re-addressing problem anyway, in which case, /48, /52, /56
> assignments should not be a big deal.
> What am I missing?

You are thinking like every other network engineer on Nanog, not like a consumer that doesn’t understand why some configurations are not possible. The only way to avoid support calls is to make it trivial for the devices to deal with just about anything that a consumer might do, and it has to be scalable enough over time to deal with the fact that a device from today will still be in use 10-15 years from now. Evolution of the rules is possible over very long timeframes, but more complex and costly. Starting with a short-sighted, managed network viewpoint is a guarantee that it will be impossible to innovate in the unmanaged home network space.


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