[358] in North American Network Operators' Group
Re: CIDR FAQ
daemon@ATHENA.MIT.EDU (Dave Siegel)
Fri Aug 18 15:17:05 1995
From: Dave Siegel <dsiegel@net99.net>
To: rrv@uiuc.edu (Ross Veach)
Date: Fri, 18 Aug 1995 11:49:08 -0700 (MST)
Cc: gwright@connix.com, nanog@MERIT.EDU
In-Reply-To: <v02120d09ac5a828207df@[192.17.16.74]> from "Ross Veach" at Aug 18, 95 01:00:21 pm
Resent-From: nanog@MERIT.EDU
> One can also accomplish this with a lot less thought by simply making each
> allocation be as far away from all other allocations as possible within a
> given CIDR block. For example, allocate xx.xx.0/24 first, xx.xx.128/24
> second, xx.xx.64/24 third, xx.xx.192/24 fourth, xx.xx.32/24 fifth, etc.
>
> If one only allocates 50% of the space using that kind of an algorithm,
> then every single prefix can be doubled to become a /23. If one only
> allocates 25% or the space, then every single prefix can be quadrupled to
> become a /22.
>
> Of course, we'd have to convince the authorities that 25% to 50%
> utilization of a CIDR block in this manner is a good thing so we could get
> new /16 or bigger blocks...
Which is the entire problem. We go through about 512 Class C's in roughly
6 weeks (at least last time I checked). The InterNIC won't give out more
CIDR blocks until we have utilized 90% or more of our blocks (read that
swipped).
We get a /15 prefix from the NIC, and in 6 weeks, it's 100% assigned, and
within 8 weeks of the initial assignment, 95% of the entire block is routing.
What I would rather do, is chop everything into little bits by relative
location to a NAP, and summarize a huge CIDR block with a specific MED (for
those that will take it). Then, it doesn't matter how message my core
get's with /22's, everything looks clean from the outside.
Dave
--
Dave Siegel Director of Engineering, Net99
http://www.webcity.com/ (602)249-1083 24x7 NOC line
http://www.rtd.com/~dsiegel/ (520)318-0696 My Tucson Office
