[ih] IP addresses are not phone numbers, was Some Questions over IPv4 Ownership

[John Levine]

>  All it takes is motivation. The phone company was motivated to
>separate phone numbers from switch ports by mobility. Is there a
>similar motivation in the IP world to make a 128 bit hex number
>permanent personal property?

I suppose that if the motivation comes along with trillions of
dollars, maybe.  In the real world, no.

RFC 3482 has a well-written overview of the way that telephone number
portability works.  Anyone interested in the topic should read it
before speculating about how it works or making analogies to other
services.  Go read it now, I'll wait.

There's a couple of rather essential differences between routing phone
calls and routing IP packets.  One is that phone numbers, unlike IP
addresses still have a great deal of geographic locality, since number
allocations are tied to geography, and number portability is limited
to within local areas.  Regardless of portability, all numbers that
start with +33 are in France, and all numbers that start +1212 are in
New York City.

This means that the phone system doesn't need anything analogous to
the Internet's backbone routers that know all 300,000 randomly
allocated IP address prefixes.  All they need is a few hundred
international country codes, or a few thousand prefixes in a
portability area.

Another rather important difference is that the phone system only
needs to do one portability lookup per phone call or per SMS.  Even
the most enthusiastic teen texter sends only a few messages per
minute, as opposed to a computer which can easily send hundreds or
thousands of IP packets per second, each of which has an IP address
that needs to be routed.

Mobile phone roaming doesn't work like number portability; it's
basically call forwarding.  No matter where in the world you go, your
phone and phone number are still tied to your home carrier.  If you
and I are standing next to each other in the US, and you call my
mobile phone which has a UK phone number, the call goes from the US to
my carrier in the UK, and then back to the US.  The home carrier needs
only to remember which network a roaming user is on, and perhaps a
routing number on that network.  Roaming databases update very slowly;
even the most peripatetic traveller is unlikely to register on more
than a few networks a day.

So while it is sort of plausible that people could have portable email
addresses using DNS lookups, e.g. whatever at user.isp.com rather than
user at isp.com, there's no way that's going to happen for IP addresses.
Fortunately, since we have the DNS, it doesn't much matter what your
IP addresses are.

R's,
John