[arin-discuss] /29 limit for ARIN SWIP whois

[Leo Bicknell]

In a message written on Sun, Jan 06, 2008 at 10:23:23AM -0500, Joe Maimon wrote:
> Is there any overriding reason to limit ARIN swip to /29 or bigger?

I will point out (in IPv4):

/32 assignment (e.g. dial up, DSL, etc) is by definition 100% utilized.

In terms of subnets, which only make sense if you have two more
more devices (router + one or more hosts):

/31 subnet by definition is 100% used.
/30 subnet by definition is 100% used (router, host, network, broadcast).
/29 subnet is at minimum 50% used (router, host, network, broadcast).
    If we further assume this was done because a /30 was not large 
    enough (e.g. people are doing the right thing) there must be at
    least 5/8's, or 62.5% in use.  Also, while the standard may be 80%
    utilization, which would require 7 of the 8 IP's to be in use;
    that leaves an interesting corner case where 5/8 and 6/8 can't 
    fit in a /30, but don't meet 80%.  Thus it makes sense to count
    5/8 and 6/8 as fully utilized, making it all but impossible to
    have an underutilized /29.

Now, one of ARIN's primary uses for the data is to insure assignments
were made in accordance with ARIN's rules when someone requests
more space.  There's no reason to review a /30, /31, or 32, as
there's no chance those assignments were under-utilized.
 
-- 
       Leo Bicknell - bicknell at ufp.org - CCIE 3440
        PGP keys at http://www.ufp.org/~bicknell/
Read TMBG List - tmbg-list-request at tmbg.org, www.tmbg.org
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