[ih] Some Questions over IPv4 Ownership

[Dave CROCKER]

On 10/14/2010 12:27 PM, David Sitman wrote:
> This summer, the Ministry of Communications in Israel began considering a change
> in ISP licensing which would require ISP's to support email address portability,
...
>      this has caused us quite a bit of consternation.


It should.

Like many appealing ideas, it suffers upon careful consideration of the changes 
needed to make it happen.

Email addressing, registration and routing each have significant design and 
operations differences from the original telephone system.  Jack's example of a 
forwarding mailbox hints at the difference:  The address is tied to a mailbox. 
If you go elsewhere, the message still has to route through the old place.  With 
telephone number portability, the actual conversation does not "go through" the 
original provider.  (There is a routing layer that is separate from the 
conversation layer, which is not true for email.)

In addition, note that the domain name portion of the email address is a "name" 
of the provider.  That carries massive semantics, in contrast with the 
neutrality of a telephone number.  One would think that portability should not 
forever tie you to the name of your original provider.

Still, it's worth asking whether it is at all practical to create email 
portability?

The answer is not only yes, but... it's been done repeatedly and without 
mandating anything:

    Create an independent service that offers "portable" addresses.  Namely, it 
just is a forwarding service.(*)  (There are elaborations of this design that 
might get clever with per-user domain names and MX records, but I'll keep it 
simple. In reality, making the lookup handling be helpfully different from the 
message transfer handling -- that is, allowing the message communications to be 
"direct" -- is actually quite difficult, at a per-user granularity, relative to 
the current system.)

    This is a value-add overlay to the existing service... with no change to the 
existing service.  As long as the forwarding service stays in business you can 
have your actual mailbox anywhere you want.

    Note that going out of business is another point of difference between the 
telephone number management system versus the email portability idea.  The 
former doesn't have to worry about continuity of service in the face of 
bankruptcy while the email one does.


d/

-- 

   Dave Crocker
   Brandenburg InternetWorking
   bbiw.net