Coexistence of advance and immediate reservation in WDM networks: Some RWA strategies

Wavelength division multiplexing (WDM) networks are advocated as a transport technology for the emerging bandwidth-intensive applications (e.g., Interactive video, ultra-high definition TV, grid computing, e-science, etc.). These applications inherent distinct features such as either delay-sensitive or delay-tolerant. Immediate reservation (IR) and advance reservation (AR) service models have been proposed for satisfying these applications demand, respectively. AR connection requests book network resources relatively far ahead than when they are utilized. The book-ahead time of AR connections not only exacerbates the provisioning rate of IR connection requests, but also results in disrupting IR connections if they are operating on the resources reserved for AR connections, once AR connections become active. To guarantee the service continuity of IR connections and efficiently utilize the network resources, this paper presents four RWA strategies for a dynamic scenario where connection requests belong to both IR and AR (fixed window) traffic demands. Each strategy exploits the connection holding-time awareness in a different way to improve the network blocking probability (BP), and eliminate disruption of IR connections. The book-ahead time of AR requests is varied to investigate its effect on the provisioning rate of AR and IR connection requests. Simulation results confirm that the proposed RWA strategies are able to improve network BP significantly. Moreover, the network total provisioning rate and consequently the resource utilization can be improved substantially by setting the book-ahead time not more than twice the mean holding-time of AR connection requests.