QoS multicasting and on-line traffic grooming in WDM optical networks

Wavelength Division Multiplexing (WDM) optical networks provide enormous bandwidth, and are promising candidates for information transmission in next generation high-speed Internet. In WDM networks, the fiber bandwidth is partitioned into multiple data channels in which different messages can be transmitted simultaneously using different wavelengths. The advances in Wavelength Division Multiplexing and fiber optic technology are seen as the key to satisfying the growing bandwidth demand in the Internet. As popularity of multicast services such as video conferencing and long distance learning continue to grow, it becomes imperative to design efficient routing and wavelength assignment algorithms to support these services. An important aspect of these real-time multimedia applications is the time dependency. The end-to-end delay Quality of Service (QoS) metric is associated with each source-destination pair and specifies the maximum permissible delay for the data traffic to reach the destination node. Establishing multicast connections with QoS constraints is an important problem in WDM optical networks. The available bandwidth on a single wavelength in current WDM based optical networks is 10 Gbps and is expected to reach 40 Gbps in the near future. However, the bandwidth requirement of practical applications is only in the sub-wavelength capacity range. Wavelengths are the critical resources in WDM networks. Thus, assigning an entire wavelength to carry only a single sub-wavelength capacity request leads to poor network utilization and undermines the network performance. Traffic grooming is a technique that is used to bridge the huge gap between the available bandwidth on a single wavelength and the user bandwidth requirement. It involves multiplexing several low speed connection requests onto a single high capacity wavelength channel. A practical wide area WDM network architecture for all-optical traffic grooming involves dividing a wavelength into multiple time slots and multiplexing different requests onto different time slots. Such a network is called as a WDM-TDM switched network or a WDM grooming network. It is important to devise new traffic grooming strategies that make better use of the available bandwidth so that the network performance can be maximized.