[arin-discuss] IPv6 End User Assignments

[michael.dillon at bt.com]

> > You have a warped sense of size and waste. A /21 is hardly massive. 
> > With IPv4 I have received several /16 allocations from ARIN, and in 
> > IPv6, a /21 or /16 represents the same proportion of the 
> total address 
> > space.
> > In the IPv4 world
> > an ISP with a /21 is a small ISP in a single town. Waste is 
> simply not 
> > an issue with IPv6.

> Only large ISP's can afford to do so with impunity. A /32 is 
> not sufficient for a default allocation of /48 per customer. 

First of all, /32 is irrelevant. You figure out how much you need
and if you are a large ISP, then you will get a /23 or /21 or 
whatever you can justify. And you justify it based on a /48 to
every customer.

But let's assume that you got a /48 and exceeded your business 
plans. Simple. When you are getting low on /48s, just go back to
ARIN and get more /32s. ARIN is not likely to runout in your
lifetime.

If and only if, you project that you will have difficulty meeting
the HD ratio when you ask for more /32s, then assign /56 to some
or all of your residential customers. This is only likely to be
a problem for the very largest ISPs.

> That makes it effectively only 16 times larger than an ipv4 
> /20, which suggests additional prefixes or renumbering pain.

No, no, no.
Your statements change nothing. An IPv6 /21 is the same proportion
of the total IPv6 space as an IPv4 /21. If an IPv4 ISP with
a /21 allocation is using a tiny amount of IPv4 space, then an
IPv6 ISP with a /21 is also using a tiny amount of space. The
difference is that only the largest ISPs will need a /21 of IPv6
space and it will last them for many years.

> People are trying to carve up their allocated space now, in 
> an intelligent manner as much as possible. Getting it right 
> at this point could avoid pain later, so this is important.

Agreed. Don't apply for a /32 until you have done some analysis
first. And if you need a bigger block than /32, get it right
from the beginning. 

--Michael Dillon