no higher-level layer requirements such as voice compres- termination of signaling and no routing of narrowband sion, silence detection/suppression, and idle channel re- calls in the IWFs. moval. AAL2 is divided into two sub-layers: the The interworked voice and data network of the future Common Part Sub-layer (CPS) and the Service Specific promises the best of all network worlds: the installed Convergence Sub-layer (SSCS). base of Frame Relay, the speed and quality of ATM, and Network infrastructure CHAPTER 3.2 the ubiquity of IP. Currently, fragmentation techniques in capitalize on the demand for digital voice? The drama is Frame Relay, IP, and ATM are quite similar, but priori- just unfolding. tization techniques, signaling protocols, and voice com- Although significant progress has been made in engi- pression algorithms are not compatible. Progress is being neering packet networks (Frame Relay, IP, and ATM) to made toward standardization within each protocol and carry voice as well as data, today's market is demanding interworking between them, but considerable work still a true convergence of these technologies into a single and remains. ubiquitous communications service without being lim- Because a comprehensive standard has not been ited by the underlying technology. The next challenge, adopted for any one technology, it is unrealistic to expect then, is to develop interconnecting and interworking the emergence of interoperability standards between standards in order to deliver voice services ubiquitously technologies in the near future. Interworking solutions over Frame Relay, IP, and ATM. will therefore have to be proprietary. It is essential that VoFR service is enabled by the use of Frame Relay the interoperability be transparent to the users, who want communications devices, such as routers or FRADs, to communicate throughout the network efficiently and configured with voice modules. These devices are without concern for the technological issues involved. sometimes referred to as Voice FRADs, or VFRAD