In many ways, ATM and Frame Relay are Similar.
Both allow PVC connections over a wan. Both allow signaling to discover and status VC's. FRF5 allows ATM to transport Frame relay. FRF8 allows ATM and Frame to interoperate.
Frame relay is defined between DDS (56k)and DS3. ATM is Defined between T-1 and OC-anything.
ATM, due to its small "MTU", is more suitable to Real time applications such as voice and video, especially at slower speeds.
Frame Relay interfaces are inexpensive, while ATM requires more expensive Hardware in order to SAR the packets into cells.
Frame relay is usually inexpensive, where ATM has historically commanded a premium price.
I'm sure I missed something. :)
