Cell Switching
The PSTN is based on time division multiplexing (TDM) and circuits of fixed capacities
In TDM certain time-slots are assigned for each connection, that means the communication is totally synchronous
In traditional telco networks frames are repeated at 125 ms intervals corresponding to the 8 kHz sampling rate of speech
The other extreme is datagram services with best-effort delivery and no bandwidth guarantees, such as LANs and IP networks which are totally asynchronous
In virtual connection based packet switched networks, band-width and some delay guarantees can be given to connections
Cells are relatively short, fixed-sized packets, which can be sent in an isochronous manner
Cell switching makes it possible to offer real-time and non-real-time services on the same network