Natting at each POP

As IPV4 space becomes more and more scarce small operators are faced how to make their IP space stretch as far as they can.  One way to do this in a routed WISP environment is to do NAT translation on a per pop basis.  I have put together a Visio diagram to illustrate this.

The router at each POP in this simplified diagram is doing the nat translation for the customers behind the single public IP address.  If you have any customers who truly need a non-shared IP you can simply route an appropriate netblock to that POP and assign public IPs out that way.  You method of assignment may vary (Static, PPPoE, DHCP, etc.). Most customers will not need a true public IP address. The XBOX Live, Playstation live, and people who want to run servers will be the main ones.

The above example is a nice compromise between assigning public IPs to everyone and being able to track customers.  If you entire network is behind a single IP address you are more prone to getting blacklisted, and having issues tracking customers from the outside.