On the DMZ (DeMilitarized Zone) the external services will be installed like a public web service. The advantage is that you can isolate the traffic from the internal servers. The firewall is set so that only traffic that is absolutely necessary is allowed from the DMZ to the internal servers. The details are written in the following articles:
17-Aug-2011: initial release. 29-Aug-2011: added apache web server. 07-Jan-2011: added nginx web server.