1. VoIP encapsulates packets into IP packets for transmission over IP enabled devices, which may or may not use Frame Relay as a transport mechansim, VoFR encapsulates voice directly into Frame Relay packets, and therefore is limited to implementation in Frame relay environments.
I believe that VoFR is somewhat more efficient, and has some good mechanisms for minimizing delay for vocie packets, and fragementing all data and voice packets,(look up FRF.11 FRF 12 on Ciscos web page), but you typicallly have to build a fully meshed frame relay environment in order rfor remote sites to call each other directly, which can certainly add to recurring cost. I prefer VoIP implementations because of the inhernet redundanant reroutable nature of IP, and because you are not loked into a fully meshed frame relay environment, or Frame relay at all for that matter, however, you probably have to be more concerned with Quality of Service mechanisms, and variable delay with A VoIP implementation.
By the way there is also Voice over ATM, but I wont get into that.
There is also IP Telephony, which is the direct encapsulation of voice traffic into IP packets as the Desk ( the phone), this should not be confused with the above three technologies, which in my humble opinion should be more aptly called convergence technologies. Of course IP telephony can and does leverage anyone of these technologies for a full solution.
2. FXOf - Foriegn Exchange Office - The counterpart is FXS Foriegn Exchange station. These two are interrelated, but think of it this way - the code, fxo or fxs is what you want to attach to - If you want to connect to a Telco (or Central office) use an FXO port. This port does not generate dial tone. If you want to hook up a fax machine in your branch to your router, use an FXS port, this port will generate dial tone for the Fax Machine.
Hope this helps,
Regards,
Gary Matteson CCIE 5101
