Thus spake "Keith Moore" <moore@xxxxxxxxxx>
NAT-PT really needs to be wiped off the face of the earth. It
provides all of the disadvantages of IPv4+NAT with all of the
transition costs of IPv6.
Indeed it does. However, it has significant benefits as well:
1) It eliminates the need for all sites to dual-stack their hosts between
the time v4 exhaustion hits and the last v4-only site disappears, which
could be a decade or more. There's also no sign this will actually happen
in time without NAT-PT, leading to fragmentation of the Internet into
v4-only and v6-only parts that can't talk to each other.
2) It may eliminate the need to dual-stack entirely; NAT-PT allows a site to
flash cut from v4 to v6 without a long transition period. This would
provide substantial cost savings to leaf site operators, many of whom are
not deploying v6 today due to the perceived cost of dual-stacking. We
remember the days of having to manage IP(v4), IPX, AppleTalk, DECnet, etc.
all on the same network and aren't looking forward to returning to that
mess.
3) Deployment of NAT-PT would instantly provide hundreds of millions of
hosts that _appeared_ to be dual-stacked, accelerating the deployment of v6
and bringing forward the day we can turn off v4 in the DFZ (even if
individual leaf sites are still v4-only internally).
If there is ever any significant penetration of NAT-PT, then the
pseudo-IPv6 network will not be able to support any more kinds of
applications than the NATted IPv4 does today.
In the beginning stages, yes. However, unlike v4 NAT, if one has a problem
with NAT-PT and how it affects applications, all one has to do is deploy v6
and they go away. Well, at least those that aren't actually caused by
having a stateful firewall...
Besides, nearly everyone is behind a v4 NAT today, so things aren't going to
get any worse for v4 traffic, and they'll gradually improve for v6 traffic
as folks deploy it and start to bypass their NAT-PT devices.
All of this "applications for v6 aren't designed to cope with NAT" stuff is
bunk. Applications are designed to use both v4 and v6 because there's no
market for v6-only apps. Apps have already paid the cost of dealing with
NAT (if it affects them) and so will future apps until we can manage to drop
v4 entirely. If NAT-PT allows us to drop v4 sooner, it's that much sooner
app developers can stop paying that cost, and that's good for everyone.
S
Stephen Sprunk "Those people who think they know everything
CCIE #3723 are a great annoyance to those of us who do."
K5SSS --Isaac Asimov
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