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

Joe Maimon jmaimon at
Fri Jan 18 18:03:53 UTC 2013

Lee Howard wrote:

> If an ISP is so close to running out of addresses that they need CGN,
> let's say they have 1 year of addresses remaining.  Given how many ports
> apps use, recommendations are running to 10:1 user:address (but I could
> well imagine that increasing to 50:1).  That means that for every user you
> NAT, you get 1/10 of an address.
> Example:  An 10,000-user ISP is growing at 10% annually.  They have 1,000
> addresses left, so they implement CGN.  You say to assuming 90% of them
> can be NATted, so next year, 100 get a unique IPv4 address, the other 900
> share 90 addresses.  At 190 addresses per year, CGN bought you five years.
> I think your 90% is high.  If it's 70%, you burn 370 per year.
> That doesn't include the fact the increased support costs, or alienated
> customer cancellations, or any of the stuff I talked about in TCO of CGN.
> Lee

2-5 years from a currently one year supply?

Factor in the current base and growth for at least another decade is 

If it works for the new subscribers, it will work for the existing ones.

Does anybody doubt that successful CGN deployment easily translates into 
many years more of v4?

We understand that there are hosts of theoretical and practical impacts. 
What we do not yet know is how the public and providers at large will 
react or adapt to these impacts.

If just the right balance of CGN negativity and resulting v6 adoption is 
the result, then we will all muddle through more or less ok.

Otherwise we will be seeing either frantic v6 migration everywhere or 
even slower pace then what we have now.


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