Packet rescheduling in real-time using token-passing protocol in WDM Ring Access Networks

This paper proposes a novel real-time packet rescheduling algorithm using a token-passing protocol to achieve QoS on a WDM Ring Access Network. The proposed rescheduling algorithm is called PEM (PDS-EAC-MTD) algorithm. The PDS (Priority-Differentiated Scheduling) algorithm deals with real-time packets, and allows them to be transmitted first, such that the front line of the prescheduled nonreal-time packets can be inserted into the queue. The EAC (Earliest Available Channel) algorithm selects the earliest available data channel, independently of the availability of the destination. The MTD (Minimum Time Difference) algorithm selects the minimum-time-to-wait channel to transmit the nonreal-time packet and is quick to establish the path of the real-time packets. The updated information including the Scheduled Data Table and the Channel Available Time Table, is then broadcasting to other access nodes using token-passing protocol to maintain the status of packet scheduling/rescheduling consistency. Overall, the PEM algorithm has the best performance over the other three algorithms, NPEM, PEE, and EATS in terms of average delay time for different traffic loads and number of channels.