Lync 2013 - Opening to the outside (federation and lync meetings)

Hi All,



I just setup Lync 2013 in our environement. I had a question regarding opening Lync 2013 to the outside world? A couple of things: 

1.) For Federation purposes

        2.) Lync Meetings

We currently have 100 employees configured for Lync. Should we setup a Edge Server (with a dedicited NAT Adddress and put on a DMZ), or do we just setup a NAT address on the server. Like I mentioned above we would like to setup a ferderation(skype, third party users) and Lync meetings. Any advice for planning this would be awesome!