Re: Waste will kill ipv6 too

[Owen DeLong <owen () delong com>]

> On Dec 28, 2017, at 14:31, Thomas Bellman <bellman () nsc liu se> wrote:
>
> > On 2017-12-28 22:31, Owen DeLong wrote:
> >
> > Sure, but that’s intended in the design of IPv6. There’s really no need
> > to think beyond 2^64 because the intent is that a /64 is a single subnet
> > no matter how many or how few machines you want to put on it.
>
> > Before anyone rolls out the argument about the waste of a /64 for a point
> > to point link with two hosts on it, please consider that the relative
> > difference in waste between a /64 with 10,000 hosts on it and a /64 with
> > 2 hosts on it is less than the rounding error in claiming that a /64 is
> > roughly 18 quintillion addresses. In fact, it’s orders of magnitude less.
>
> [...]
>
> > We may, someday, wish we had gone to some value of N larger than 128,
> > but I seriously doubt it will occur in my lifetime.
>
> My problem with the IPv6 addressing scheme is not the waste of 64 bits
> for the interface identifier, but the lack of bits for the subnet id.
> 16 bits (as you normally get a /48) is not much for a semi-large organi-
> zation, and will force many to have a dense address plan, handing out
> just one or a few subnets at a time, resulting in a patch-work of
> allocations.  24 bits for subnet id would be more usable.

That’s absurd. The intent is a /48 per end SITE. Not per organization. According to ARIN policies, the definition of an 
end site is a single building or structure or a single tenant within a multi-tenant building or structure.

With nibble boundary round-up in policy, an organization with more than one site can get at least 16 /48s. Further, a 
university could (technically) get a /48 for every dorm room. 

> Consider e.g. a university or company campus.  There are probably at
> least 16 departments, so I would like to use 8 bits as department id.
> Several departments are likely to have offices on more than one floor,
> or in more than one building, so I would like to let them have 4 bits
> to specify location, and then 8 bits to specify office/workplace within
> each location.  And allow them to hand out 16 subnets per workplace.
> That adds up to 24 bits.  So a /40 would be nice, not a /48.

A campus is, by definition multiple end sites. 

> Similarly, an ISP that wants a structured address plan, e.g. to encode
> prefecture, city and part of city in the address, will quickly use up
> bits in the customer id part of the address.

An ISP can qualify for up to a /12 in a single allocation. They get two levels of hierarchy at which they can aggregate 
and do a nibble-boundary round-up.

As such, I’m not sure how many bits you want for that that you feel you can’t have. Remember, /32 is just the default 
no questions asked minimum v6 isp allocation. Not the maximum. I know of at least three isps that have /24s or more of 
ipv6 space. 


>    /Bellman

Owen