Traffic scheduling with per VC QoS guarantee in WDM networks

The future broadband network has to support wide range of applications with diverse service requirements, exemplified by the rigorous efforts in the development of the next generation integrated service Internet (IPng) and B-ISDN ATM. The existing proposals in the design of WDM networks have largely focused on supporting a single type of service, whether it is circuit switching or datagram, and relatively less attention has been given to guaranteeing the quality-of-service (QoS) of individual traffic stream at each station. This paper explores the possibility of providing an integrated service directly at the WDM optical layer while taking into consideration the unique QoS requirement from individual traffic stream. We introduce a framework based on a hierarchical link scheduling mechanism, one is to schedule packets from applications to the transmission queue of a station, the other is to schedule the actual packet transmissions among multiple stations. We show such separation is essential for achieving scalability in that a large user population can be accommodated, and for offering flexibility in that optimal scheduling algorithms can be designed in different level best tuned to the specific system requirements. The results show that the proposed mechanism is indeed capable of providing QoS guarantee for both real-time and non-real-time applications while at the same time achieving high overall throughput