Naming, Addressing, and IPv6
Steve Silverman
Houston Associates

The IETF has always been somewhat unorthodox in their use of the term “address.” In IPv4, one 32-bit field (dubbed an address) is used for both routing and identification. In IPv6, the address has been significantly updated (to 128 bits) but the confusing use of the term “address” has been maintained. This article will attempt to clarify the issue.
 
Terminology
In standard usage, a name or identification points to a particular person (or piece of equipment). If the person moves to a new location, their name stays the same.
 
An address tells one how to find a particular location. If I first live in Virginia and then move to California, I keep my name but change my address so mail or visitors can find me. The function of an address is to enable a package (or packet) to be routed to that location. The address must be assigned in accordance with the way the network works or certain "expenses" are increased. This will be discussed below.

 IPv6
IPv6 is defined as having a 128 bit address. What is often overlooked is that half of that address, 64 bits, is an endpoint identifier (RFC3587) that always stays the same (i.e., a name). Only the upper 64 bits are an address in the usual meaning of the term. One consequence of this is that the address space is large (1019) but not quite as large as some depictions indicate. This is not to say we're going to run out of addresses in the near future, but we shouldn't get too sloppy in throwing around the address space.
 
Separation of Naming and Addressing
This separation of naming and addressing allows several useful functions. While IPv4 allowed some mobility, IPv6's separation of ID and routing makes it much easier to implement mobile terminals. We still tend to assign the address to the terminal rather than to the person. One possibility is a personal identity card that could signal your presence to nearby terminals, which would in turn signal your home agent. My prediction is that 20 years from now, we will take for granted a level of transparent reachability for each person that is barely conceivable today. The dark side of this is loss of privacy and the intrusion that accompanies such reachability. If the network can find you to receive a call, it knows where you are. Perhaps people may learn to use the off button on the phone or the identity card.
 
One major business opportunity is a "phone butler" that screens phone calls, makes appointments, discards spam and junk phone calls, and lets emergency calls through. Let us hope that this miracle of artificial intelligence, processing power, and battery conservation arrives before the spammers do.