[ih] Why did location/identity separation not happen? (Was: Internet without entrenched factions?)

[John Levine]

It appears that Dave Crocker via Internet-history <dhc at dcrocker.net> said:
>> That choice helps, but does not guarantee, uniqueness, but also 
>> results in some pragmatic problems - such as the difficulty of moving 
>> your mailbox from one ISP, corporation, or organization to another. 
>> Humans still try to contact me using email addresses from decades 
>> ago.  There is no "email portability" scheme analogous to the 
>> telephone system's number portability.
>
>Well, sort of, yes there is.  There are services supporting an email 
>address that is independent of the ISP mailbox you use. They are, of 
>course, just aliasing services.   Besides some commercial example, 
>alumni email address mechanisms do this.

The telco equivalent would be call forwarding which is a real thing but not the
same.

Number portability tried a variety of approaches as described in RFC 3482 and
ended up adding a level of indirection into the call setup process. It also
changed the meaning of phone numbers. They used to be like IP addresses, with
the leading digits identifying a switch, and the trailing digits the number on
that switch. Now they're more like email addresses. At call time the calling
system or a nearby tandem looks up the called number, now called the directory
number (DN) and finds a location routing number (LRN) to identify the switch. If
the number hasn't been ported it'll be the same number, while if it has been
ported it'll be a number assigned to the switch. Then it routes the call as it
used to but using LRN to find the switch, and the switch uses the DN to identify
the subscriber.

This worked for phone numbers because telcos are regulated so the regulators
could order the telcos to do it. Also, phone numbers have a fixed simple format,
a sequence of digits between N and M length, so it's straightforward if
expensive to build the forwarding database. Neither is true for e-mail*, so
forwarding is the best we're going to get.

Even within telephony there's limits to portability. North America is unusual in
that there is a single unified number space for fixed and mobile, so you can
port between the two. In most countries, fixed and mobile numbers are in
separate number spaces so you can port from one mobile carrier to another, but
not between fixed and mobile. 

North America has geographic rate centers, and currently you can only port
between carriers in the same rate center. The large mobile carriers are present
nearly everywhere so that doesn't matter for them, but there's ongoing arguments
about if and how to provide nationwide portability for landline and small mobile
carriers.

R's,
John

* - if you want to forward foobar at example.com, do you also forward
foo.bar at example.com, and foobar-ext at example.com? Or maybe example.com and
example.net have the same set of mailboxes so you'd forward both. Only the
target system knows.