On 27/08/13 08:06, Roland Perry wrote:
In message , at 20:59:48 on Mon, 26
Aug 2013, John Williamson remarked:
Dynamic IP addresses are a hangover from the days of dial-up links,
where you only went on line for as long as you needed to download,
say, new posts to newsgroups you followed. As you were charged by the
time you spent connected, you then went off-line to read and compose
your replies, then you connected again to send you replies and read
new posts. In this way, the telco only need one IP address for ten or
so subscribers.

It's a bit simpler than that - each modem had a static IP address, and
the subscriber inherited that IP address for the duration of their
session.

maybe originally. But that vanished when banks of modems were replaced
by kit that plugged straight into BT supplied trunks, and radius servers
came in.

In fact even when it was banks of modems connected to computers I cant
recall there was necessarily a 'one per modem' IP allocation. PPP auth
has generally been bound to the user, not the actual interface when
stiing up IP addresses.


Some schemes existed to allow people to dial specific modems (rather
than get a random one from a hunt group) which would mean they had a
more consistent IP address.

And of course some ISPs went one stage further and routed their
network such that subscribers were allocated a personalised static IP
address. In those days IP addresses were in copious supply for any ISP
who wanted to do that.
Except that now with 90% of people permanently connected everyone DOES
essentially have an IP address - it just gets reallocated from time to
time on dynamic setups.

And again, with the way backhaul is now run over ATM circuits, there is
no need for any 'geographical' routing of IP packets to a given
DSLAM. The ISP throws the IP packet into the ATM cloud and the routing
to the DSLAM is done with ATM routing handled typically by BTs ATM network.

Its not that way for cable though, which is why cable customers have IP
addresses that are related to the local cable hubs.

--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to lead are elected by the least capable of producing, and where the members of society least likely to sustain themselves or succeed, are rewarded with goods and services paid for by the confiscated wealth of a diminishing number of producers.