IPv6 end user addressing

Thu Aug 11 01:33:46 UTC 2011

On Wed, Aug 10, 2011 at 8:40 PM, Mark Andrews <marka at isc.org> wrote:
> No.  A typical user has 10 to 20 addresses NAT'd to one public address.

I'd say this is fair.  Amazingly enough, it all basically works right
with one IP address today.  It will certainly be nice to have the
option to give all these devices public IP addresses, or even have a
few public subnets; but it does require more imagination than any of
us have demonstrated to figure out how any end-user will need more
than 2^8 subnets.  That's still assuming that device-makers won't
decide they need to be able to operate with subnets of arbitrary size,
rather than fixed-size /64 subnets.

> There was a concious decision made a decade and a half ago to got to
> 128 bits instead of 64 bits and give each subnet 64 bits so we would
> never have to worry about the size of a subnet again.  IPv6 is about
> managing networks not managing addresses.

Thanks for the explanation of how to subnet IPv4 networks and use
RFC1918.  I hope most readers are already familiar with these
concepts.  You should note that IPv6 was not, in fact, originally
envisioned with /64 subnets; that figure was to be /80 or /96.  In the
mid-1990s, it was believed that dramatically increasing the number of
bits available for ISP routing flexibility was very beneficial, as
well as making access subnets so big that they should never need to
grow.  Then SLAAC came along.  Except SLAAC doesn't do necessary
things that DHCPv6 does, and the cost of implementing things like
DHCPv6 in very small, inexpensive devices has gone down dramatically.

I am amazed that so few imagine we might, in within the lifetime of
IPv6, like to have more bits of address space for routing structure
within ISP networks; but these people do think that end-users need
1.2e+24 addresses for the devices they'll have in their home.

I don't have to use my imagination to think of ways that additional
bits on the network address side would have been advantageous -- all I
need is my memory.  In the 90s, it was suggested that a growing number
of dual-homed networks cluttering the DFZ could be handled more
efficiently by setting aside certain address space for customers who
dual-homed to pairs of the largest ISPs.  The customer routes would
then not need to be carried by anyone except those two ISPs, who are
earning money from the customer.  This never happened for a variety of
good reasons, but most of the technical reasons would have gone away
with the adoption of IPv6, as it was envisioned in the mid-90s.

There seems to be a lot of imagination being used for SOHO networks,
and none on the ISP side.  What a shame that is.

Owen, I do agree with the point you made off-list, that if huge
mistakes are made now and the IPv6 address space is consumed more
rapidly than the community is comfortable with, there should be plenty
of opportunity to fix that down the road.

-- 
Jeff S Wheeler <jsw at inconcepts.biz>
Sr Network Operator  /  Innovative Network Concepts