The telephone number situation in the United States
has been one of continual crisis for years, because
of rapid growth in use (in part because of Internet
access!). The area served by a given "area code" would
be split into smaller areas with multiple area codes;
these days, those areas aren't necessarily even contiguous.
That is mostly because the telco(s) tried to impose a fixed address length
on a scheme that really should have remained variable. Telephone numbers
overseas are truly variable. When you dial 011+3, the remaining digits can
be anywhere from one to a thousand. The local end just stores them all
until you say you are done (by pausing or hitting the # key), and then it
routes it as far as it can, and passes the rest onto some other node.
I'd suggest that address assignment policy should
keep process lightweight, so that it is realistic for
businesses to regularly ask for assignments in more
granular chunks ...
But if you use a truly variable scheme, you don't have to assign anything at
all.
Say Company X wants some addresses, and it is in an area where all addresses
start with 9482. You just add some digits, tell them what they are, and
they can add as many addresses as they want behind those digits. All you
have to care about is that 94825xxxxx gets routed to Company X. The rest of
the address allocation is their business. They might have just two digits
on the end, or they might have forty.
With fixed-length addresses, you're in trouble as soon as you make an
assignment. You might assign 94820000 through 94829999 to Company X. The
problem is that, if Company X needs only 200 addresses, you've wasted 9800
addresses, and you can't give them to anyone else. Conversely, if Company X
ever needs more than 10000 addresses, you have to completely reallocate
everything, or fragment their address range. Either way, you lose.
... big users would be willing to request another 256
when the new branch office opens, then another 64 for
the summer interns...
All well and good, except that it fragments the address space, making it
impossible to route on just a portion of the address--you have to start
looking at the entire address, all the time.
-- Anthony