On woensdag, apr 30, 2003, at 18:20 Europe/Amsterdam, Stephen Sprunk
wrote:
this is an interesting point, but I think it has more to do with
whether
the prefixes are statically bound to customers than the length of
those
prefixes.
Of course.
why would giving customers static /64s result in fewer
routes in your IGP than giving them static /48s?
I was suggesting nothing of the sort; just assumed that _if_ you're
going to give a customer something fixed it would be a /48 while a
dynamic /48 doesn't make much sense the way things are now.
IMHO, dialup is a bad example because static IPs per customer are rare;
let's switch to the cable/dsl market.
Standard practice is to connect all customers in a given area (or
signed up
in a given period) to a single concentrator via some sort of virtual
circuit
(PPPoE, ATM, FR, etc). This concentrator then internally bridges all
of
these virtual circuits into a single subnet with a single prefix,
giving you
one route for N customers.
Ok, I'm not all that familiar with cable/ADSL, but isn't this more
often done by giving each customer a virtual point to point link? In
the case of PPP over ethernet I don't see how it could work otherwise.
Now of course you can then proxy ARP...
OTOH, if you assign a prefix to each customer,
you then have between N+1 and 2N routes for N customers.
Unless you aggregate, of course. For cable/ADSL that shouldn't be a
problem as the customers conveniently stay in the same place. :-) Not
so with dial.
The latter might
be justified if we're truly committed to eliminating NATs, but it
costs a
lot more in routes, in administration, and in address waste (assigning
a /48
to what is, in nearly all cases, 1-4 hosts).
So we should give them a /126???
I guess a /64 would be enough for most people. You are underestimating
the number of hosts, though: don't forget about IP phones, IP radios
and stuff like that. And I'm not even counting more obscure examples
such as IP refrigirators.