On physical frame time-slot switching over DWDM

The merging trend of three separate networks, i.e. telephone, cable TV and computer networks, demands underlying communication systems to provide a mechanism to transmit and switch bit streams at very high speed, and to satisfy different users\´ QoS requirements. DWDM, with its transmission rate at tens of tera bits per second in a single fiber, becomes the most promising candidate for such convergence. However, switching techniques in DWDM have not yet fledged for such a merged high-speed network. We present a novel concept called the physical frame time-slot switching (PFTS). With PFTS, transmission time of a fixed-length physical frame is defined as a "time-slot", and used for multiplexing a single lambda channel and for user data switching over a DWDM platform. A maximum length of Ethernet MAC frame is exactly fitted into a PFT (physical frame time-slot), and one or more PFT(s) can be assigned to a time-critical user data stream according to required QoS parameters, such as throughput and time delay. PFT switching operates in an asynchronous mode on the basis of single PFT in a lambda; and hence eliminates the need of lambda switching and global synchronization among clocks in a network. In an "out-band signaling" network, PFTS enables user data transfer platform to be reduced to a single physical layer.