Network Address Translation (NAT) and Port
Address Translation (PAT) were developed as
solutions to the diminishing availability of IP
addresses. NAT and PAT, as implemented today in
many network routers, allow a company or user to
share a single or a few assigned public IP addresses
among many private addresses (which are not
bound by an address authority).
Although these schemes preserve address space
and provide anonymity, the benefits come at the
cost of individuality. This eliminates the very reason
for networking (and the Internet): allowing peer-topeer
collaboration through shared applications.
IP version 6 (IPv6) provides an answer to the
problem of running out of address space. It also
allows for the restoration of a true end-to-end
model in which hosts can connect to each other
unobstructed and with greater flexibility. Some of
the key elements of IPv6 include allowing each
host to have a unique global IP address, the ability
to maintain connectivity even when in motion and
roaming, and the ability to natively secure host
communications.