[arin-ppml] "Millions of Internet Addresses Are Lying Idle" (slashdot)

[Leo Bicknell]

In a message written on Sat, Oct 18, 2008 at 09:01:17PM +0000, Paul Vixie wrote:
> "The most comprehensive scan of the entire internet for several decades
> shows that millions of allocated addresses simply aren't being
> used. Professor John Heidemann from the University of Southern California

Unfortunately while I might even give him that this is the most
comprehensive, I believe there are more than a few severe holes in
it that mean it may not be representative.

A large problem is that many hosts will not respond to unsolicited
ICMP, TCP, or other packets.  Indeed, many hosts today are protected
by multiple levels of this, service providers helpfully dropping
some packets before a organization based firewall dropping some
more, followed by a host based firewall dropping the rest.  I have
no doubt that millions of computers were missed as a result.

However, the larger problem is that this is the entirely wrong
definition of "in use".  Let's take a simple example of a University.
They may have wired dorm rooms, students with laptops, and wifi
enabled classrooms.  If you ping at 11AM, the classroom IP's respond,
and the dorm ones do not, if you ping at 11PM, the dorm rooms
respond, the classrooms do not.  And if you ping at 12 noon when
they are all walking to lunch almost none of either respond.

This survey equates in use to be having a computer actively using
it and responding at the time of the probe.  I would submit that
is a very poor definition.  The dorm room block and classroom blocks
are both "in use" every day, and unfortunately the technology
involved does not make it possible to move back and forth.

In fact, the interesting thing to do here is simple.  Cross reference
the "pingable" IP's in a block of space with requests over the past
month to google, or akamai, or updates.microsoft.com and see what
percentage of the "unpingable" IP's are in fact in use on a regular
basis.  We could haggle over if "in use" means active in the last
day, week, or month, if it really matters.

A pretty chart for sure; in terms of being helpful for planning the
future, it's borderline chart junk.

-- 
       Leo Bicknell - bicknell at ufp.org - CCIE 3440
        PGP keys at http://www.ufp.org/~bicknell/
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