On Fri, Nov 22, 2013 at 11:59 AM, Ted Lemon
<ted(_dot_)lemon(_at_)nominum(_dot_)com> wrote:
On Nov 22, 2013, at 11:46 AM, Noel Chiappa
<jnc(_at_)mercury(_dot_)lcs(_dot_)mit(_dot_)edu>
wrote:
CGNs are expensive. Why would people prefer to maintain them if the
IPv6 infrastructure was working?
Cheaper than customer service calls.
That's almost certainly true now. I'm not talking about now. Really,
the big problem with CGNs is that they don't scale—this is why lw4over6 and
MAP represent a significant and useful innovation.
They will scale fine just like the dialup pools have scaled fine.
If the switchover is managed right, there will be no difference between the
functionality of an IPv6+CGN connection and an IPv4 connection. At some
point in the future, maybe in 5 years time, the IPv6+CGN connection will be
on the modern hardware and have the better performance than the legacy IPv4
connection and that is what will create demand to switch.
As the transition continues the percentage of the net that can only be
reached through IPv4 will decline from the current 95% to more like 5%. As
that happens, the load on the CGNs will gradually fall as less traffic
needs to be routed through them.
There was a time when the Internet was serviced mostly though 48Kb modems.
providers had rack upon rack of the thing and were doubling capacity every
12 months back in '95. But then the demand started to taper off and these
days it is legacy technology.
Or to look at it another way, the entire PSTN system plus SIP is nothing
more than a giant legacy transition infrastructure right now. Eventually
even the telephone numbers will go away.
Building carrier grade NAT and carrier grade gateways is essentially the
same problem. People might build boxes that only do one but anyone buying
them is taking a risk that they are not going to be forced into upgrading
them to support transition to IPv6.
One of the consequences of what happened yesterday in the US Senate is that
the Republican party just lost their ability to block appointment of FCC
commissioners who support and judges who recognize the right of the FCC to
implement policies to promote net neutrality and technical standards to
promote competition.
What I expect to see happen in the market is that in the next decade, CGN
will start to seem old-fashioned, and more and more what will be deployed
will be stateless port-sharing NAT hardware in the core, supported by
stateful NATs at the CP, just like we were doing before the CGN idea got
popular.
The nice thing about stateless NATs in the core is that they can be scaled
up and down according to need. So as more traffic is carried over the
native IPv6 network, you can start switching off boxes in the core. You
can track the demand, so you don't switch off boxes that are needed. You
can even goose the switchover by running your IPv4 NATs closer to capacity,
forcing traffic that could go over either transport to go over v6, because
it's working better, and Happy Eyeballs can tell.
--
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