[ppml] My view on IPv4 (was: Re: IPv4 wind-down)

Michel Py michel at arneill-py.sacramento.ca.us
Mon Apr 2 23:54:48 EDT 2007

Hi Iljitsch,

> Iljitsch van Beijnum wrote:
> It will be the kind of NAT where a service provider puts 10,
> 100 or even 1000 customers behind a single IP address, and
> the number of usable TCP ports starts being a problem.

This is not as bad as it appears. I have some customers with 100 to 300
PCs out of a single IP and I never saw the number of simultaneous ports
above 1K out of a possible 64K.

> Forget about port mappings

There are easy solutions: you are customer #3245, ports 32450 to 32459
are NATted to your IP, configure your P2P apps to use these ports.

> and hence any applications that are more complex than client-server.

As long as 95% of the users are ok with that, there is no problem. What
does Joe User care? Email, surfing, P2P, and Skype. The same way
applications have been made NAT friendly, they will be made 2xNAT
friendly. Specifically, applications that open 50 ports at a time will
be pointed out and will either adapt or die, just like apps that can't
cross NAT have become confidential.

> We need the water to boil at some point so the frog jumps out.

I agree, but I project that 10K hosts behind a /28 and possibly /29 NAT
pool will cause no major issues, therefore the water is not going to get
hot any time soon. Emerging markets in countries that don't have enough
IPv4 will not be made of geeks who want their own IP address, and double
NAT will remain the solution in a world where not having v4 is not an

> In other words: the running out of IPv4 space is a
> necessary requisite for wide scale IPv6 adoption.
> Without it, nothing is going to change.

If your goal is IPv6 deployment, I agree. I would point out though that
most businesses and users are not IPv6 evangelists, they don't care if
IPv6 is adopted, and they will continue to do what they have done so
far: go the cheap route, which is heavily NATted v4.

> Therefore, any policy that seeks to artifically avoid running out
> is harmful because it perpetuates an address starvation model. 

And any policy that seeks to artificially accelerate the running out is
suicide, because it will take all the people that rely on v4 out of
their lethargy to oppose it.

> - it's unfair that more than 50% of all IPv4 address space
> is held by US entities which then get to make a lot of money
> from them, while the developing world holds next to no address
> space and would have to buy it from richer countries.

Making money has never been about being fair.


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