classful routes redux

Mon Nov 7 19:38:22 UTC 2005

Thus spake <Michael.Dillon at btradianz.com>
> 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.

And let's not forget that various parts of that "thin layer" connect to each 
other in something approaching a partial mesh with no transitive 
reachability.

While I doubt that it's anywhere near enough to account for all the "MIA" 
ASNs, nor do we have any way of knowing for sure, but many of those folks 
cannot get by with private ASNs for those networks for the same reason they 
can't use RFC1918 space.  Others give in and use static routes and 
double-NATs.

S

Stephen Sprunk        "Stupid people surround themselves with smart
CCIE #3723           people.  Smart people surround themselves with
K5SSS         smart people who disagree with them."  --Aaron Sorkin 