Quoting RFC2860 [Re: I-D Action:draft-azinger-scalable-addressing-00.txt]

[michael.dillon at bt.com]

> 	this points out that global uniqueness is important to Fred (and
> me too)
> 	but that assured / presumed _full_ connectivity is less so. 

On the Community Of Interest Networks (COIN) that my employer operates
for the global financial community (RadianzNet) and other companies
operate for aviation (SITA) and the automotive industry (ENX, ANX)
global uniqueness is very important, but any sort of external connectivity
is often forbidden. COINs sit in a middle ground between the Internet and
SCADA networks. A SCADA network has no business being connected to anything
other than a very tightly closed and restricted control network. A COIN
may choose to have some limited connectivity with the Internet. In the case 
of RadianzNet which I know best, just about every one of the several hundred
networks connected to us, also have connections to the Internet. It's just
that we enforce a policy of no direct traffic interchange. For example, 
an Internet connected site cannot exchange FIX traffic directly with a site
on RadianzNet even though there are wires and routers in existence that 
*could* provide connectivity. Instead they must use a FIX service provider
that has connectivity to both the Internet and RadianzNet.

I think that the general architecture of COINs is common in the world of
business and commerce, and one could liken them to the VANs which were
larger than the global Internet until around 1999. Some COINs like
RadianzNet, SITA, ENX/ANX are very visible but I think there are lots
of smaller ones and many so-called extranets connecting the trading
partners of a large company, share the main characteristic of COINs
in that they require globally unique addresses but do not require any
connectivity guarantees with the public Internet.

Globally unique addresses are required because the interconnect mesh
of COINs is constantly changing. New businesses connect to the network,
mergers happen, and all of these hundreds of networks cannot use 
a set aside private network addressing block unless it is very large
and guarantees no collisions. In the IPv4 world, the RFC 1918 block
is so small that many global companies have run out of private network
addresses or are on the verge of running out, or have implemented
multi-layered NAT to reuse RFC 1918 addressing internally. For IPv6
expectations are higher, and since there is no shortage of globally
unique addresses, there is no good reason not to use them.

As for routing slots, COINS have minimal impact. Most ASes that
participate in a COIN will also have Internet connectivity as
well and will use routing policy and firewalls to control
traffic.

--Michael Dillon