On the support of bandwidth on demand service over wide-area WDM optical networks
Future broadband networks must support integrated services and offer flexible bandwidth usage. Most existing proposals for wide-area wavelength division multiplexed (WDM) networks employ circuit switching adopting the concept of lightpath, in which each circuit or lightpath occupies an entire wavelength. This, however, is not suited for end-to-end transport of information streams, typically with each stream having its unique traffic characteristics such as the bandwidth needed, different traffic bursty nature, and diverse service requirements. We explore the extensions of the functions of what we refer as the optical link control (OLC) layer, native on top of optical layer, to offer finer granularity of wavelength usage and further enable the possibility of bandwidth on-demand (BoD) service directly over WDM networks. The objective is to facilitate the support of integrated services over WDM networks and to mitigate the changes needed in the upper layers as well. The proposed approach attempts to exploit the strengths of both optics and electronics, in which packets are either routed end-to-end over a lightpath transparently, or forwarded from wavelength to wavelength by electronic switching, whenever required. Furthermore, in order to establish an end-to-end BoD connection, the issue of how to select the best wavelength to route the given connection is also investigated. The effectiveness of the proposal is evaluated by simulation.