IP over WDM traffic engineering

Traffic engineering in IP/WDM networks can be pursued in two fashions: overlay and integrated. With overlay traffic engineering, operations in one layer can be independent from those in the other layer. Traffic engineering solutions developed for either IP networks or WDM networks can be directly applied to each layer, respectively. At the present stage, an anticipated first step towards IP over WDM is to hook up IP router interfaces to optical add/drop multiplexer client add/drop ports. This forms an overlay network in which WDM serves as the server layer and IP behaves like the client layer. This overlay client-server network is a natural match to the notion of overlay traffic engineering. With integrated traffic engineering, optimization with respect to selected objectives is pursued coordinately across both the IP and WDM layers. It is made possible by mechanisms such as multi-protocol lambda switching that allows a unified control plane across both layers. With the emergence of more sophisticated hardware that integrates functionality of both IP and WDM at each network element, integrated traffic engineering can be performed more naturally and efficiently.