The need for high bandwidth in today's IP-based Internet, and the promise of WDM to provide this high capacity, is fueling the current investigations on IP-over-[attachment=142]
WDM networks. Internet growth not only requires providing immense bandwidth but also triggers the need for providing the guarantees with respect to quality of service, security, and fault tolerance. Currently telecommunication networks use SONET/SDH for transmission, multiplexing and protection. It is implemented over WDM. As a result we are using the IP over SONET/SDH over WDM. The alternative approach is IP directly over WDM bypassing the SONET/SDH layer. This approach will give the advantages of overall reduction of equipment cost and management complexity. It will also improve the bandwidth efficiency. The issue that must be addressed in such a network is effective interoperation of IP and WDM. This could involve changes in either layer to take the advantages of other. Here the critical challenge is to provide the capability to instantiate and route lightpaths in real time and to support a variety of protection and restoration scheme. This involved efficient control mechanism and traffic engineering, which need be interoperable with existing technology.