and industry networking standards including X.25 as network performance at configurable central, regional and local an interface to packet mode devices, X.31 for access to ISDN levels. This page intentionally left blank Fast packet switching K L Moran B Sc (Hons) CEng MIEE Sprint International Contents 55.1 Introduction 55/3 Frame Relay 55/3 Cell Relay 55/6 Conclusions 55/9 55.5 References 55/10 This page intentionally left blank Introduction 55/3 55.1 Introduction handle all types of transmission, not just data; as well as providing much higher transmission speeds within the 150 to 600 megabits per The telecommunications industry is currently being driven by second range. Now, applications that depend on high bandwidth can switching technology which is changing at an ever increasing pace. co-exist on the same network, as well as the low speed (64kb/s and The demand for high capacity systems is becoming increasingly less) data applications addressed by traditional packet switched important for providing both sophisticated networking applications networks. and offering flexible new services. Fast Packet Switching is a new digital communications approach Today's carrier systems, E1 (2.048Mb/s) in Europe and T1 that is revolutionising communications networking strategies, and (1.5Mb/s) in the United States, provide a popular choice for net- proprietary FPS implementations are already widely used in the US working voice traffic and data employing Time Division Multiplex- and gaining momentum internationally. There is however some ing (TDM) techniques. This is due mainly to the functionality and confusion surrounding the term 'Fast Packet Switching'. It is cost savings that intelligent TDMs offer, and the fact that there have usually taken as a concept covering Frame Relay and Cell Relay not been any other alternatives; that is until Fast Packet Switching technologies, as illustrated in Figure 55.1. came onto the scene. Frame Relay uses a variable length frame, and as such creates In today's corporate networks voice t