classful routes redux

Mon Nov 7 10:57:39 UTC 2005

> What about those that are assigned and used but not [currently] visible
> on the public Internet [i.e., are on other internets]?

Indeed!

On Henk's slide number 5 he states:

"Each AS wants to be able to send traffic to any other AS"

This is NOT true. Many ASes explicitly do *NOT*
want to send traffic to any other AS. They only want
to send traffic to customers, vendors or business 
partners of some sort. In other words, there are many
so-called extranets which are basically internets
built using exactly the same technology as the Internet
however with more restrictive interconnect policies.

One way to visualize this is to imagine the Internet
as a cloud. At the core of the cloud are the core 
providers and at the edge of the cloud are the end 
user organizations, many of which appear to be
singly homed. However, hidden behind this edge is
a thin layer which represents a private internet.
It also connects many networks but it does *NOT*
exchange traffic with the public Internet. All the 
networks connected to these private internets are
also connected to the public Internet but they 
implement strict traffic separation policies 
internally. In some cases, this is an air gap but
these days it is often a bunch of firewalls.

In the 24/7 connected world of the 21st century
there is a lot of growth in these internets that
wrap around the Internet but don't exchange vital
fluids with it.

--Michael Dillon