[ppml] PIv6 for legacy holders (/w RSA + efficient use)

[michael.dillon at bt.com]

> With IPv4, NAT allows one to isolate most of the internal 
> network by using non-routable addresses.  So, switching ISPs 
> means renumbering the external nodes and revising some firewall rules.
> 
> With IPv6, without NAT, switching vendors with PA space means 
> renumbering both the external and the internal network.

With IPv6, ULA addressing defined in RFC 4193
http://www.ietf.org/rfc/rfc4193.txt allows one to isolate most of the
internal network using non-routable addresses. Combine that with the
typical enterprise configuration of firewall, web proxy, and internal
email service. You don't even need NAT in this scenario.

--Michael Dillon