Date: Wed, 16 May 2001 17:43:10 +0300 (EEST)
From: Pekka Savola <[EMAIL PROTECTED]>
Message-ID: <[EMAIL PROTECTED]>
| The problem is that if dialups, adsl's etc. should be given /48, but the
| organization is allocated one /48, how do you proceed? Take for example
| universities offering dialup, or companies doing it for the personnel;
This depends upon the environment. In some cases there is essentially an
ISP in existence, which should have a /35 (or whatever that turns out to be)
from which to hand out pieces, one of which would be a /48 for itself, and
the rest for its "customers".
In most cases however (such as the university that employs me), the subnets
handed out to dial ins are just a part of our network (they are for v4, and
will remain so for v6), and are all managed together - dial in users get
as much address space as they need (and independent of the technology that
they use to connect). I have a subnet for home from that space which is
just as much as I need. Because of the relationship that exists all this
is pretty easy to manage - that is, that the subnet happens to exist in
my house doesn't make it any difficult than a subnet that exists in some
university owned building.
Students we tend to push towards using a commercial ISP though in general,
it makes lots of sense all around.
But note that I wasn't advocating a /48 for every dial up user - I think that
much smaller allocations will work fine for almost all (down to /64)
low end connections (clearly a /64 will work for everyone with only a
single subnet at the other end, provided the routing is managed correctly).
What is important is to make available the address space that people
actually need - and not to be too bothered about their rationale for their
needs (up to as big as /48 allocations anyway) - if they think they need it,
allocate it, just default to smaller for people who have no idea.
(A question on the ISP form might be "Do you need more than a hundred million
addresses?").
| This might lead to an increased size of routing tables as you
| might not be able to aggregate the prefixes properly.
The original model had the ISP returning their /35 (after an overlap
period) when they get given the /32 (or /33 or /29 or whatever it is)
when they have outgrown it, precisely to avoid this problem. Of course,
this means that all of their customers need to renumber. This kind
of thing was the prime motivation for making renumbering practically
possible, and comparatively easy - not the "I want to change ISPs and
don't want to have to renumber" which is of rather lower importance
(anything caused by a voluntary action is much easier to deal with than
something you have to do without choice and without any obvious benefits).
kre
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