It sounds like we are fairly certain that homes and some small
businesses will be given prefixes longer than /48 by their providers.
Are we also convinced that those small networks will require the
address independence feature provided by NAT66? I guess this question
boils down to whether we expect two (or more) hosts within a small
network to communicate directly with each other using global IPv6
addresses.
If we do need to address prefixes of longer than /48 in NAT66, that is
fairly easy to do. We just need to pick which sacrifices we are
willing to make. I can think of two choices:
(1) Add the checksum correction to a 2byte portion of the lower 64
bits when the prefix is longer than /48, thus modifying the IID. This
wouldn't be compatible with (currently unspecified) mechanisms that
require a constant IID, but we would already have that problem with
nodes that generate privacy addresses.
or
(2) Fix the UDP or TCP checksum instead of performing the checksum
correction algorithm when the prefix is longer than /48. The cost
here is that we lose the ability to encrypt/protect the transport
layer headers. In NAT66, we could explicitly make this correction for
UDP/TCP only, passing through other transport layers unmodified, which
might help to reduce the impact on new innovations at the transport
layer.
Margaret
On Mar 30, 2009, at 12:17 PM, Mark Townsley wrote:
My experience is that those brand new to IPv6 (and who don't do some
reading up front) first think of offering a /128, but are quickly
convinced that /64 is the real minimum (which is why I said I had
never seen one "seriously" consider a /128). Then, after some time,
they can be convinced to move the line up to a /56, but it takes a
second push - one that's a little bit harder than the first. Going
further, to a /48, is often a tough sell for residential.
That's my experience at least, YMMV. I've never actually seen a
residential /128 service, though I have seen /64, /60, /56 and /48.
- Mark
Marc Blanchet wrote:
Mark Townsley a écrit :
I'm in contact with a lot of broadband providers deploying and
thinking
about deploying IPv6, and have never seen one seriously consider /
128.
/64, yes. /60 certainly. But never /128.
I'm too "in contact with a lot of broadband providers deploying and
thinking about deploying IPv6".
and some were first thinking to give a /128 as the "basic service",
even
after some education on how "IPv6 works"... The possible arrival of
6ai/nat66 has already bring back this notion of /128, since it "just
maps" with their current v4 deployment/billing/OSS/...
note that I don't think /128+nat66-6ai is a good idea, but I would
certainly be careful claiming that it would not happen or it is not
on
the design table.
Marc.
- Mark
Wes Beebee (wbeebee) wrote:
... And ISP's could just say "we're only handing out one /128"
because
we're expecting you to deploy NAPT66 - and there are plenty of
vendors
willing to sell NAPT66 boxes...
- Wes
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