Design of the Internet backbone

- Router : TCP/IP 2nd layer related, switching device (ATM, Frame Relay), traffic engineering, the products are most expensive 

- SONET/SDH: very high speed fiber optic network technology (more information)

- WDM/DWDM: advanced optical network technology. Dense wavelength division multiplexing (DWDM) technology to offer a comprehensive, flexible, and scalable transport solution that reduces network costs (more information)