Frame Relay is a technology that exists from 1988 (more or less). Ethernet is older (mid 70's).
Why we classify as a WAN technology Frame Relay if Ethernet can do the same (and even better!)?
As far as I understand, with ATM it's almost the same...
I really don't understand the use of Frame Relay or ATM to interconnect two networks in the WAN world because we can do it with Ethernet connections (i.e. a L2 Ethernet switch).
It is because the need of being able to transmit both voice and data and the time-frame of this technologies?
If I need to connect two IP LANs I would do it using a router or a switch so... why these technologies? What is changing if I need to connect two networks in the "WAN world"?