This paper describes recent experiences with evaluating and implementing advanced intermetwork communication protocols on top of ATM. First, performance results with conventional TCP IP over ATM based on Digital Equipment's Gigaswitch/ATM are reported. It becomes obvious that current protocols must be tuned specifically in order to exploit ATM performance. In order to address advanced quality of service issues based on resource reservation, the paper describes an implementation of IPng (IP next generation) and RSVP (Resource Reservation Protocol) over ATM. Solutions for mapping quality of service and traffic parameters in an adequate way are presented. Moreover, the issue of address mapping from IPng onto ATM is discussed. Implementation results and experiences in these areas are illustrated. Finally, ongoing current work on resource reservation in advance is presented. It is outlined that longer-term resource planning and scheduling provides additional benefits for selected ATM applications.