Using WDM Technology to Carry IP Traffic

In this paper, we consider three options for using WDM (Wavelength Division Multiplexing) technology to carry IP traffic. First, WDM multiplexers/demultiplexers (transmission technology) can be used on direct physical links between IP routers to increase the transmission bandwidth of fibers. Second, WDM networking technology (with reconfigurable add/drop multiplexers, crossconnects, and tunable lasers) can be used in a provisioned mode, where lightpaths are established a priori. Third, WDM networks can be used in a switched mode, where lightpaths are set up and released on demand. We address the user-plane protocol stack problem and routing problem in all three cases. We conclude that the first option is clearly a winner as already proven in its widespread use. The success of the second option for carrying IP traffic is dependent on (i) whether equipment costs for WDM can be kept lower than with other networking technologies, and (ii) whether traffic shaping is possible at the edges of the WDM circuit-switched network to enable it to carry bursty self-similar IP traffic in a bandwidth-efficient manner when compared to other networking technologies. Finally, we proposed the use of the third option for large file transfers, which is an application for which circuit switching is a better networking alternative than packet switching.