Voice over IP and Voice over ATM
Voice over IP will be one of the driving factors of the next years of internetworking
In local networks Voice over IP already is a working solution (e.g. for Cisco on their new campus in Silicon Valley)
In the wide area, the availability, security and QoS of IP networks is not yet on-par with the requirements of voice
RSVP, DiffServ and many other schemes promise a solution to the QoS problem
ATM was designed for (among other things) voice and the CBR or VBR services can be used for that purpose
Nevertheless, voice is still rarely run directly over ATM, a more common solution is to have Voice over IP take advantage of the QoS provided by an underlying ATM service
Voice over ATM is a working solution today, in the long run I would be my money on Voice over IP and DiffServ