Slashdot: UK ISP PlusNet Testing Carrier-Grade NAT Instead of IPv6

Joe Maimon jmaimon at
Fri Jan 18 04:58:46 UTC 2013

Owen DeLong wrote:

> And this is where you run off the rails… You are assuming that NAT today
> and CGN provide similar functionality from an end-user perspective.

To the extent that CGN functions like the clueless linksys daisy-chain, 
then yes it does.
> The reality is that they do not. CGN is a substantially more degraded
> form of internet access than current traditional per-site NAT.
> 1.	The end-site does not control the NAT box.

The vast majority of end site today either do not control the NAT box or 
do not know how to control the NAT box.

> 2.	UPnP and NAT-PMP do NOT work through CGN.

And without this wondrous technology, nothing works behind a NAT! 
Whatever did we do before the invention and mass adoption of UPnP and 

> 3.	There is no other provision in most CGNs to allow for inbound
> 	connection trickery that allows many of today's applications to
> 	function in spite of NAT.

Clearly we have run out of trickery as multiple layers of NAT stumps 
even the finest of our tricksters.

We will have to wait and see on this one. There is a complex interaction 
between protocol development, application deployment, cpe technology and 
user behavior all influenced by the NAT reality we are all witness to.

Will this interaction adopt and adapt CGN? Clearly your opinion is not, 
but its only an opinion.

>> Wireless has - remind me - how many /8's compared to, say, Google?
> Are you sure that 75% of VZW's IP addresses are assigned to end-customer
> devices? I am not.

No, actually, I believe what he said is that OF the Addresses ASSIGNED 
to devices, 75% are end-customers.

Far more are likely not in use by any specific device at any given point 
in time.

And what else exactly would VZW  be doing with those addresses? Running 
more servers and infrastructure then wireless clients to use them?

> First, it's more like 1/100 customers that are not already behind NAT
> of some form, so your 37 years drops to 0.37 years (a little more than
> 4 months).

Rather disingenuous of you. We are not addressing "some form" of nat. We 
are addressing the specific form of CGN. Of which far fewer then 1/100 
customers are behind.

How about much simpler math. Assume 75% IP in any provider organization 
are for subscribers. Assume an average 5-10 subscribers per CGN IP.

Clearly, that organization's subscriber growth will be limited by CGN 
technology, not by address scarcity.

> This seems very disruptive and rather heavy on the overhead for a 4-month
> stop-gap.
 > Owen

Think locally for a bit. Addresses are not instantaneously fungible 
across the internet. Any provider who can pull this off will have far 
more then a 4-month stop-gap. They may even have enough to peddle on the 


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